1config ARCH 2 string 3 option env="ARCH" 4 5config KERNELVERSION 6 string 7 option env="KERNELVERSION" 8 9config DEFCONFIG_LIST 10 string 11 depends on !UML 12 option defconfig_list 13 default "/lib/modules/$UNAME_RELEASE/.config" 14 default "/etc/kernel-config" 15 default "/boot/config-$UNAME_RELEASE" 16 default "$ARCH_DEFCONFIG" 17 default "arch/$ARCH/defconfig" 18 19config CONSTRUCTORS 20 bool 21 depends on !UML 22 23config IRQ_WORK 24 bool 25 26config BUILDTIME_EXTABLE_SORT 27 bool 28 29menu "General setup" 30 31config BROKEN 32 bool 33 34config BROKEN_ON_SMP 35 bool 36 depends on BROKEN || !SMP 37 default y 38 39config INIT_ENV_ARG_LIMIT 40 int 41 default 32 if !UML 42 default 128 if UML 43 help 44 Maximum of each of the number of arguments and environment 45 variables passed to init from the kernel command line. 46 47 48config CROSS_COMPILE 49 string "Cross-compiler tool prefix" 50 help 51 Same as running 'make CROSS_COMPILE=prefix-' but stored for 52 default make runs in this kernel build directory. You don't 53 need to set this unless you want the configured kernel build 54 directory to select the cross-compiler automatically. 55 56config COMPILE_TEST 57 bool "Compile also drivers which will not load" 58 default n 59 help 60 Some drivers can be compiled on a different platform than they are 61 intended to be run on. Despite they cannot be loaded there (or even 62 when they load they cannot be used due to missing HW support), 63 developers still, opposing to distributors, might want to build such 64 drivers to compile-test them. 65 66 If you are a developer and want to build everything available, say Y 67 here. If you are a user/distributor, say N here to exclude useless 68 drivers to be distributed. 69 70config LOCALVERSION 71 string "Local version - append to kernel release" 72 help 73 Append an extra string to the end of your kernel version. 74 This will show up when you type uname, for example. 75 The string you set here will be appended after the contents of 76 any files with a filename matching localversion* in your 77 object and source tree, in that order. Your total string can 78 be a maximum of 64 characters. 79 80config LOCALVERSION_AUTO 81 bool "Automatically append version information to the version string" 82 default y 83 help 84 This will try to automatically determine if the current tree is a 85 release tree by looking for git tags that belong to the current 86 top of tree revision. 87 88 A string of the format -gxxxxxxxx will be added to the localversion 89 if a git-based tree is found. The string generated by this will be 90 appended after any matching localversion* files, and after the value 91 set in CONFIG_LOCALVERSION. 92 93 (The actual string used here is the first eight characters produced 94 by running the command: 95 96 $ git rev-parse --verify HEAD 97 98 which is done within the script "scripts/setlocalversion".) 99 100config HAVE_KERNEL_GZIP 101 bool 102 103config HAVE_KERNEL_BZIP2 104 bool 105 106config HAVE_KERNEL_LZMA 107 bool 108 109config HAVE_KERNEL_XZ 110 bool 111 112config HAVE_KERNEL_LZO 113 bool 114 115config HAVE_KERNEL_LZ4 116 bool 117 118choice 119 prompt "Kernel compression mode" 120 default KERNEL_GZIP 121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 122 help 123 The linux kernel is a kind of self-extracting executable. 124 Several compression algorithms are available, which differ 125 in efficiency, compression and decompression speed. 126 Compression speed is only relevant when building a kernel. 127 Decompression speed is relevant at each boot. 128 129 If you have any problems with bzip2 or lzma compressed 130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 131 version of this functionality (bzip2 only), for 2.4, was 132 supplied by Christian Ludwig) 133 134 High compression options are mostly useful for users, who 135 are low on disk space (embedded systems), but for whom ram 136 size matters less. 137 138 If in doubt, select 'gzip' 139 140config KERNEL_GZIP 141 bool "Gzip" 142 depends on HAVE_KERNEL_GZIP 143 help 144 The old and tried gzip compression. It provides a good balance 145 between compression ratio and decompression speed. 146 147config KERNEL_BZIP2 148 bool "Bzip2" 149 depends on HAVE_KERNEL_BZIP2 150 help 151 Its compression ratio and speed is intermediate. 152 Decompression speed is slowest among the choices. The kernel 153 size is about 10% smaller with bzip2, in comparison to gzip. 154 Bzip2 uses a large amount of memory. For modern kernels you 155 will need at least 8MB RAM or more for booting. 156 157config KERNEL_LZMA 158 bool "LZMA" 159 depends on HAVE_KERNEL_LZMA 160 help 161 This compression algorithm's ratio is best. Decompression speed 162 is between gzip and bzip2. Compression is slowest. 163 The kernel size is about 33% smaller with LZMA in comparison to gzip. 164 165config KERNEL_XZ 166 bool "XZ" 167 depends on HAVE_KERNEL_XZ 168 help 169 XZ uses the LZMA2 algorithm and instruction set specific 170 BCJ filters which can improve compression ratio of executable 171 code. The size of the kernel is about 30% smaller with XZ in 172 comparison to gzip. On architectures for which there is a BCJ 173 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 174 will create a few percent smaller kernel than plain LZMA. 175 176 The speed is about the same as with LZMA: The decompression 177 speed of XZ is better than that of bzip2 but worse than gzip 178 and LZO. Compression is slow. 179 180config KERNEL_LZO 181 bool "LZO" 182 depends on HAVE_KERNEL_LZO 183 help 184 Its compression ratio is the poorest among the choices. The kernel 185 size is about 10% bigger than gzip; however its speed 186 (both compression and decompression) is the fastest. 187 188config KERNEL_LZ4 189 bool "LZ4" 190 depends on HAVE_KERNEL_LZ4 191 help 192 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. 193 A preliminary version of LZ4 de/compression tool is available at 194 <https://code.google.com/p/lz4/>. 195 196 Its compression ratio is worse than LZO. The size of the kernel 197 is about 8% bigger than LZO. But the decompression speed is 198 faster than LZO. 199 200endchoice 201 202config DEFAULT_HOSTNAME 203 string "Default hostname" 204 default "(none)" 205 help 206 This option determines the default system hostname before userspace 207 calls sethostname(2). The kernel traditionally uses "(none)" here, 208 but you may wish to use a different default here to make a minimal 209 system more usable with less configuration. 210 211config SWAP 212 bool "Support for paging of anonymous memory (swap)" 213 depends on MMU && BLOCK 214 default y 215 help 216 This option allows you to choose whether you want to have support 217 for so called swap devices or swap files in your kernel that are 218 used to provide more virtual memory than the actual RAM present 219 in your computer. If unsure say Y. 220 221config SYSVIPC 222 bool "System V IPC" 223 ---help--- 224 Inter Process Communication is a suite of library functions and 225 system calls which let processes (running programs) synchronize and 226 exchange information. It is generally considered to be a good thing, 227 and some programs won't run unless you say Y here. In particular, if 228 you want to run the DOS emulator dosemu under Linux (read the 229 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 230 you'll need to say Y here. 231 232 You can find documentation about IPC with "info ipc" and also in 233 section 6.4 of the Linux Programmer's Guide, available from 234 <http://www.tldp.org/guides.html>. 235 236config SYSVIPC_SYSCTL 237 bool 238 depends on SYSVIPC 239 depends on SYSCTL 240 default y 241 242config POSIX_MQUEUE 243 bool "POSIX Message Queues" 244 depends on NET 245 ---help--- 246 POSIX variant of message queues is a part of IPC. In POSIX message 247 queues every message has a priority which decides about succession 248 of receiving it by a process. If you want to compile and run 249 programs written e.g. for Solaris with use of its POSIX message 250 queues (functions mq_*) say Y here. 251 252 POSIX message queues are visible as a filesystem called 'mqueue' 253 and can be mounted somewhere if you want to do filesystem 254 operations on message queues. 255 256 If unsure, say Y. 257 258config POSIX_MQUEUE_SYSCTL 259 bool 260 depends on POSIX_MQUEUE 261 depends on SYSCTL 262 default y 263 264config CROSS_MEMORY_ATTACH 265 bool "Enable process_vm_readv/writev syscalls" 266 depends on MMU 267 default y 268 help 269 Enabling this option adds the system calls process_vm_readv and 270 process_vm_writev which allow a process with the correct privileges 271 to directly read from or write to another process' address space. 272 See the man page for more details. 273 274config FHANDLE 275 bool "open by fhandle syscalls" 276 select EXPORTFS 277 help 278 If you say Y here, a user level program will be able to map 279 file names to handle and then later use the handle for 280 different file system operations. This is useful in implementing 281 userspace file servers, which now track files using handles instead 282 of names. The handle would remain the same even if file names 283 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 284 syscalls. 285 286config USELIB 287 bool "uselib syscall" 288 default y 289 help 290 This option enables the uselib syscall, a system call used in the 291 dynamic linker from libc5 and earlier. glibc does not use this 292 system call. If you intend to run programs built on libc5 or 293 earlier, you may need to enable this syscall. Current systems 294 running glibc can safely disable this. 295 296config AUDIT 297 bool "Auditing support" 298 depends on NET 299 help 300 Enable auditing infrastructure that can be used with another 301 kernel subsystem, such as SELinux (which requires this for 302 logging of avc messages output). Does not do system-call 303 auditing without CONFIG_AUDITSYSCALL. 304 305config HAVE_ARCH_AUDITSYSCALL 306 bool 307 308config AUDITSYSCALL 309 bool "Enable system-call auditing support" 310 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL 311 default y if SECURITY_SELINUX 312 help 313 Enable low-overhead system-call auditing infrastructure that 314 can be used independently or with another kernel subsystem, 315 such as SELinux. 316 317config AUDIT_WATCH 318 def_bool y 319 depends on AUDITSYSCALL 320 select FSNOTIFY 321 322config AUDIT_TREE 323 def_bool y 324 depends on AUDITSYSCALL 325 select FSNOTIFY 326 327source "kernel/irq/Kconfig" 328source "kernel/time/Kconfig" 329 330menu "CPU/Task time and stats accounting" 331 332config VIRT_CPU_ACCOUNTING 333 bool 334 335choice 336 prompt "Cputime accounting" 337 default TICK_CPU_ACCOUNTING if !PPC64 338 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 339 340# Kind of a stub config for the pure tick based cputime accounting 341config TICK_CPU_ACCOUNTING 342 bool "Simple tick based cputime accounting" 343 depends on !S390 && !NO_HZ_FULL 344 help 345 This is the basic tick based cputime accounting that maintains 346 statistics about user, system and idle time spent on per jiffies 347 granularity. 348 349 If unsure, say Y. 350 351config VIRT_CPU_ACCOUNTING_NATIVE 352 bool "Deterministic task and CPU time accounting" 353 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 354 select VIRT_CPU_ACCOUNTING 355 help 356 Select this option to enable more accurate task and CPU time 357 accounting. This is done by reading a CPU counter on each 358 kernel entry and exit and on transitions within the kernel 359 between system, softirq and hardirq state, so there is a 360 small performance impact. In the case of s390 or IBM POWER > 5, 361 this also enables accounting of stolen time on logically-partitioned 362 systems. 363 364config VIRT_CPU_ACCOUNTING_GEN 365 bool "Full dynticks CPU time accounting" 366 depends on HAVE_CONTEXT_TRACKING 367 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN 368 select VIRT_CPU_ACCOUNTING 369 select CONTEXT_TRACKING 370 help 371 Select this option to enable task and CPU time accounting on full 372 dynticks systems. This accounting is implemented by watching every 373 kernel-user boundaries using the context tracking subsystem. 374 The accounting is thus performed at the expense of some significant 375 overhead. 376 377 For now this is only useful if you are working on the full 378 dynticks subsystem development. 379 380 If unsure, say N. 381 382config IRQ_TIME_ACCOUNTING 383 bool "Fine granularity task level IRQ time accounting" 384 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL 385 help 386 Select this option to enable fine granularity task irq time 387 accounting. This is done by reading a timestamp on each 388 transitions between softirq and hardirq state, so there can be a 389 small performance impact. 390 391 If in doubt, say N here. 392 393endchoice 394 395config BSD_PROCESS_ACCT 396 bool "BSD Process Accounting" 397 depends on MULTIUSER 398 help 399 If you say Y here, a user level program will be able to instruct the 400 kernel (via a special system call) to write process accounting 401 information to a file: whenever a process exits, information about 402 that process will be appended to the file by the kernel. The 403 information includes things such as creation time, owning user, 404 command name, memory usage, controlling terminal etc. (the complete 405 list is in the struct acct in <file:include/linux/acct.h>). It is 406 up to the user level program to do useful things with this 407 information. This is generally a good idea, so say Y. 408 409config BSD_PROCESS_ACCT_V3 410 bool "BSD Process Accounting version 3 file format" 411 depends on BSD_PROCESS_ACCT 412 default n 413 help 414 If you say Y here, the process accounting information is written 415 in a new file format that also logs the process IDs of each 416 process and it's parent. Note that this file format is incompatible 417 with previous v0/v1/v2 file formats, so you will need updated tools 418 for processing it. A preliminary version of these tools is available 419 at <http://www.gnu.org/software/acct/>. 420 421config TASKSTATS 422 bool "Export task/process statistics through netlink" 423 depends on NET 424 depends on MULTIUSER 425 default n 426 help 427 Export selected statistics for tasks/processes through the 428 generic netlink interface. Unlike BSD process accounting, the 429 statistics are available during the lifetime of tasks/processes as 430 responses to commands. Like BSD accounting, they are sent to user 431 space on task exit. 432 433 Say N if unsure. 434 435config TASK_DELAY_ACCT 436 bool "Enable per-task delay accounting" 437 depends on TASKSTATS 438 help 439 Collect information on time spent by a task waiting for system 440 resources like cpu, synchronous block I/O completion and swapping 441 in pages. Such statistics can help in setting a task's priorities 442 relative to other tasks for cpu, io, rss limits etc. 443 444 Say N if unsure. 445 446config TASK_XACCT 447 bool "Enable extended accounting over taskstats" 448 depends on TASKSTATS 449 help 450 Collect extended task accounting data and send the data 451 to userland for processing over the taskstats interface. 452 453 Say N if unsure. 454 455config TASK_IO_ACCOUNTING 456 bool "Enable per-task storage I/O accounting" 457 depends on TASK_XACCT 458 help 459 Collect information on the number of bytes of storage I/O which this 460 task has caused. 461 462 Say N if unsure. 463 464endmenu # "CPU/Task time and stats accounting" 465 466menu "RCU Subsystem" 467 468choice 469 prompt "RCU Implementation" 470 default TREE_RCU 471 472config TREE_RCU 473 bool "Tree-based hierarchical RCU" 474 depends on !PREEMPT && SMP 475 help 476 This option selects the RCU implementation that is 477 designed for very large SMP system with hundreds or 478 thousands of CPUs. It also scales down nicely to 479 smaller systems. 480 481config PREEMPT_RCU 482 bool "Preemptible tree-based hierarchical RCU" 483 depends on PREEMPT 484 help 485 This option selects the RCU implementation that is 486 designed for very large SMP systems with hundreds or 487 thousands of CPUs, but for which real-time response 488 is also required. It also scales down nicely to 489 smaller systems. 490 491 Select this option if you are unsure. 492 493config TINY_RCU 494 bool "UP-only small-memory-footprint RCU" 495 depends on !PREEMPT && !SMP 496 help 497 This option selects the RCU implementation that is 498 designed for UP systems from which real-time response 499 is not required. This option greatly reduces the 500 memory footprint of RCU. 501 502endchoice 503 504config SRCU 505 bool 506 help 507 This option selects the sleepable version of RCU. This version 508 permits arbitrary sleeping or blocking within RCU read-side critical 509 sections. 510 511config TASKS_RCU 512 bool "Task_based RCU implementation using voluntary context switch" 513 default n 514 select SRCU 515 help 516 This option enables a task-based RCU implementation that uses 517 only voluntary context switch (not preemption!), idle, and 518 user-mode execution as quiescent states. 519 520 If unsure, say N. 521 522config RCU_STALL_COMMON 523 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE ) 524 help 525 This option enables RCU CPU stall code that is common between 526 the TINY and TREE variants of RCU. The purpose is to allow 527 the tiny variants to disable RCU CPU stall warnings, while 528 making these warnings mandatory for the tree variants. 529 530config CONTEXT_TRACKING 531 bool 532 533config RCU_USER_QS 534 bool "Consider userspace as in RCU extended quiescent state" 535 depends on HAVE_CONTEXT_TRACKING && SMP 536 select CONTEXT_TRACKING 537 help 538 This option sets hooks on kernel / userspace boundaries and 539 puts RCU in extended quiescent state when the CPU runs in 540 userspace. It means that when a CPU runs in userspace, it is 541 excluded from the global RCU state machine and thus doesn't 542 try to keep the timer tick on for RCU. 543 544 Unless you want to hack and help the development of the full 545 dynticks mode, you shouldn't enable this option. It also 546 adds unnecessary overhead. 547 548 If unsure say N 549 550config CONTEXT_TRACKING_FORCE 551 bool "Force context tracking" 552 depends on CONTEXT_TRACKING 553 default y if !NO_HZ_FULL 554 help 555 The major pre-requirement for full dynticks to work is to 556 support the context tracking subsystem. But there are also 557 other dependencies to provide in order to make the full 558 dynticks working. 559 560 This option stands for testing when an arch implements the 561 context tracking backend but doesn't yet fullfill all the 562 requirements to make the full dynticks feature working. 563 Without the full dynticks, there is no way to test the support 564 for context tracking and the subsystems that rely on it: RCU 565 userspace extended quiescent state and tickless cputime 566 accounting. This option copes with the absence of the full 567 dynticks subsystem by forcing the context tracking on all 568 CPUs in the system. 569 570 Say Y only if you're working on the development of an 571 architecture backend for the context tracking. 572 573 Say N otherwise, this option brings an overhead that you 574 don't want in production. 575 576 577config RCU_FANOUT 578 int "Tree-based hierarchical RCU fanout value" 579 range 2 64 if 64BIT 580 range 2 32 if !64BIT 581 depends on TREE_RCU || PREEMPT_RCU 582 default 64 if 64BIT 583 default 32 if !64BIT 584 help 585 This option controls the fanout of hierarchical implementations 586 of RCU, allowing RCU to work efficiently on machines with 587 large numbers of CPUs. This value must be at least the fourth 588 root of NR_CPUS, which allows NR_CPUS to be insanely large. 589 The default value of RCU_FANOUT should be used for production 590 systems, but if you are stress-testing the RCU implementation 591 itself, small RCU_FANOUT values allow you to test large-system 592 code paths on small(er) systems. 593 594 Select a specific number if testing RCU itself. 595 Take the default if unsure. 596 597config RCU_FANOUT_LEAF 598 int "Tree-based hierarchical RCU leaf-level fanout value" 599 range 2 RCU_FANOUT if 64BIT 600 range 2 RCU_FANOUT if !64BIT 601 depends on TREE_RCU || PREEMPT_RCU 602 default 16 603 help 604 This option controls the leaf-level fanout of hierarchical 605 implementations of RCU, and allows trading off cache misses 606 against lock contention. Systems that synchronize their 607 scheduling-clock interrupts for energy-efficiency reasons will 608 want the default because the smaller leaf-level fanout keeps 609 lock contention levels acceptably low. Very large systems 610 (hundreds or thousands of CPUs) will instead want to set this 611 value to the maximum value possible in order to reduce the 612 number of cache misses incurred during RCU's grace-period 613 initialization. These systems tend to run CPU-bound, and thus 614 are not helped by synchronized interrupts, and thus tend to 615 skew them, which reduces lock contention enough that large 616 leaf-level fanouts work well. 617 618 Select a specific number if testing RCU itself. 619 620 Select the maximum permissible value for large systems. 621 622 Take the default if unsure. 623 624config RCU_FANOUT_EXACT 625 bool "Disable tree-based hierarchical RCU auto-balancing" 626 depends on TREE_RCU || PREEMPT_RCU 627 default n 628 help 629 This option forces use of the exact RCU_FANOUT value specified, 630 regardless of imbalances in the hierarchy. This is useful for 631 testing RCU itself, and might one day be useful on systems with 632 strong NUMA behavior. 633 634 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 635 636 Say N if unsure. 637 638config RCU_FAST_NO_HZ 639 bool "Accelerate last non-dyntick-idle CPU's grace periods" 640 depends on NO_HZ_COMMON && SMP 641 default n 642 help 643 This option permits CPUs to enter dynticks-idle state even if 644 they have RCU callbacks queued, and prevents RCU from waking 645 these CPUs up more than roughly once every four jiffies (by 646 default, you can adjust this using the rcutree.rcu_idle_gp_delay 647 parameter), thus improving energy efficiency. On the other 648 hand, this option increases the duration of RCU grace periods, 649 for example, slowing down synchronize_rcu(). 650 651 Say Y if energy efficiency is critically important, and you 652 don't care about increased grace-period durations. 653 654 Say N if you are unsure. 655 656config TREE_RCU_TRACE 657 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) 658 select DEBUG_FS 659 help 660 This option provides tracing for the TREE_RCU and 661 PREEMPT_RCU implementations, permitting Makefile to 662 trivially select kernel/rcutree_trace.c. 663 664config RCU_BOOST 665 bool "Enable RCU priority boosting" 666 depends on RT_MUTEXES && PREEMPT_RCU 667 default n 668 help 669 This option boosts the priority of preempted RCU readers that 670 block the current preemptible RCU grace period for too long. 671 This option also prevents heavy loads from blocking RCU 672 callback invocation for all flavors of RCU. 673 674 Say Y here if you are working with real-time apps or heavy loads 675 Say N here if you are unsure. 676 677config RCU_KTHREAD_PRIO 678 int "Real-time priority to use for RCU worker threads" 679 range 1 99 if RCU_BOOST 680 range 0 99 if !RCU_BOOST 681 default 1 if RCU_BOOST 682 default 0 if !RCU_BOOST 683 help 684 This option specifies the SCHED_FIFO priority value that will be 685 assigned to the rcuc/n and rcub/n threads and is also the value 686 used for RCU_BOOST (if enabled). If you are working with a 687 real-time application that has one or more CPU-bound threads 688 running at a real-time priority level, you should set 689 RCU_KTHREAD_PRIO to a priority higher than the highest-priority 690 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO 691 value of 1 is appropriate in the common case, which is real-time 692 applications that do not have any CPU-bound threads. 693 694 Some real-time applications might not have a single real-time 695 thread that saturates a given CPU, but instead might have 696 multiple real-time threads that, taken together, fully utilize 697 that CPU. In this case, you should set RCU_KTHREAD_PRIO to 698 a priority higher than the lowest-priority thread that is 699 conspiring to prevent the CPU from running any non-real-time 700 tasks. For example, if one thread at priority 10 and another 701 thread at priority 5 are between themselves fully consuming 702 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be 703 set to priority 6 or higher. 704 705 Specify the real-time priority, or take the default if unsure. 706 707config RCU_BOOST_DELAY 708 int "Milliseconds to delay boosting after RCU grace-period start" 709 range 0 3000 710 depends on RCU_BOOST 711 default 500 712 help 713 This option specifies the time to wait after the beginning of 714 a given grace period before priority-boosting preempted RCU 715 readers blocking that grace period. Note that any RCU reader 716 blocking an expedited RCU grace period is boosted immediately. 717 718 Accept the default if unsure. 719 720config RCU_NOCB_CPU 721 bool "Offload RCU callback processing from boot-selected CPUs" 722 depends on TREE_RCU || PREEMPT_RCU 723 default n 724 help 725 Use this option to reduce OS jitter for aggressive HPC or 726 real-time workloads. It can also be used to offload RCU 727 callback invocation to energy-efficient CPUs in battery-powered 728 asymmetric multiprocessors. 729 730 This option offloads callback invocation from the set of 731 CPUs specified at boot time by the rcu_nocbs parameter. 732 For each such CPU, a kthread ("rcuox/N") will be created to 733 invoke callbacks, where the "N" is the CPU being offloaded, 734 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 735 "s" for RCU-sched. Nothing prevents this kthread from running 736 on the specified CPUs, but (1) the kthreads may be preempted 737 between each callback, and (2) affinity or cgroups can be used 738 to force the kthreads to run on whatever set of CPUs is desired. 739 740 Say Y here if you want to help to debug reduced OS jitter. 741 Say N here if you are unsure. 742 743choice 744 prompt "Build-forced no-CBs CPUs" 745 default RCU_NOCB_CPU_NONE 746 depends on RCU_NOCB_CPU 747 help 748 This option allows no-CBs CPUs (whose RCU callbacks are invoked 749 from kthreads rather than from softirq context) to be specified 750 at build time. Additional no-CBs CPUs may be specified by 751 the rcu_nocbs= boot parameter. 752 753config RCU_NOCB_CPU_NONE 754 bool "No build_forced no-CBs CPUs" 755 help 756 This option does not force any of the CPUs to be no-CBs CPUs. 757 Only CPUs designated by the rcu_nocbs= boot parameter will be 758 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 759 kthreads whose names begin with "rcuo". All other CPUs will 760 invoke their own RCU callbacks in softirq context. 761 762 Select this option if you want to choose no-CBs CPUs at 763 boot time, for example, to allow testing of different no-CBs 764 configurations without having to rebuild the kernel each time. 765 766config RCU_NOCB_CPU_ZERO 767 bool "CPU 0 is a build_forced no-CBs CPU" 768 help 769 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 770 callbacks are invoked by a per-CPU kthread whose name begins 771 with "rcuo". Additional CPUs may be designated as no-CBs 772 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 773 All other CPUs will invoke their own RCU callbacks in softirq 774 context. 775 776 Select this if CPU 0 needs to be a no-CBs CPU for real-time 777 or energy-efficiency reasons, but the real reason it exists 778 is to ensure that randconfig testing covers mixed systems. 779 780config RCU_NOCB_CPU_ALL 781 bool "All CPUs are build_forced no-CBs CPUs" 782 help 783 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 784 boot parameter will be ignored. All CPUs' RCU callbacks will 785 be executed in the context of per-CPU rcuo kthreads created for 786 this purpose. Assuming that the kthreads whose names start with 787 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 788 on the remaining CPUs, but might decrease memory locality during 789 RCU-callback invocation, thus potentially degrading throughput. 790 791 Select this if all CPUs need to be no-CBs CPUs for real-time 792 or energy-efficiency reasons. 793 794endchoice 795 796config RCU_EXPEDITE_BOOT 797 bool 798 default n 799 help 800 This option enables expedited grace periods at boot time, 801 as if rcu_expedite_gp() had been invoked early in boot. 802 The corresponding rcu_unexpedite_gp() is invoked from 803 rcu_end_inkernel_boot(), which is intended to be invoked 804 at the end of the kernel-only boot sequence, just before 805 init is exec'ed. 806 807 Accept the default if unsure. 808 809endmenu # "RCU Subsystem" 810 811config BUILD_BIN2C 812 bool 813 default n 814 815config IKCONFIG 816 tristate "Kernel .config support" 817 select BUILD_BIN2C 818 ---help--- 819 This option enables the complete Linux kernel ".config" file 820 contents to be saved in the kernel. It provides documentation 821 of which kernel options are used in a running kernel or in an 822 on-disk kernel. This information can be extracted from the kernel 823 image file with the script scripts/extract-ikconfig and used as 824 input to rebuild the current kernel or to build another kernel. 825 It can also be extracted from a running kernel by reading 826 /proc/config.gz if enabled (below). 827 828config IKCONFIG_PROC 829 bool "Enable access to .config through /proc/config.gz" 830 depends on IKCONFIG && PROC_FS 831 ---help--- 832 This option enables access to the kernel configuration file 833 through /proc/config.gz. 834 835config LOG_BUF_SHIFT 836 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 837 range 12 21 838 default 17 839 depends on PRINTK 840 help 841 Select the minimal kernel log buffer size as a power of 2. 842 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 843 parameter, see below. Any higher size also might be forced 844 by "log_buf_len" boot parameter. 845 846 Examples: 847 17 => 128 KB 848 16 => 64 KB 849 15 => 32 KB 850 14 => 16 KB 851 13 => 8 KB 852 12 => 4 KB 853 854config LOG_CPU_MAX_BUF_SHIFT 855 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 856 depends on SMP 857 range 0 21 858 default 12 if !BASE_SMALL 859 default 0 if BASE_SMALL 860 depends on PRINTK 861 help 862 This option allows to increase the default ring buffer size 863 according to the number of CPUs. The value defines the contribution 864 of each CPU as a power of 2. The used space is typically only few 865 lines however it might be much more when problems are reported, 866 e.g. backtraces. 867 868 The increased size means that a new buffer has to be allocated and 869 the original static one is unused. It makes sense only on systems 870 with more CPUs. Therefore this value is used only when the sum of 871 contributions is greater than the half of the default kernel ring 872 buffer as defined by LOG_BUF_SHIFT. The default values are set 873 so that more than 64 CPUs are needed to trigger the allocation. 874 875 Also this option is ignored when "log_buf_len" kernel parameter is 876 used as it forces an exact (power of two) size of the ring buffer. 877 878 The number of possible CPUs is used for this computation ignoring 879 hotplugging making the compuation optimal for the the worst case 880 scenerio while allowing a simple algorithm to be used from bootup. 881 882 Examples shift values and their meaning: 883 17 => 128 KB for each CPU 884 16 => 64 KB for each CPU 885 15 => 32 KB for each CPU 886 14 => 16 KB for each CPU 887 13 => 8 KB for each CPU 888 12 => 4 KB for each CPU 889 890# 891# Architectures with an unreliable sched_clock() should select this: 892# 893config HAVE_UNSTABLE_SCHED_CLOCK 894 bool 895 896config GENERIC_SCHED_CLOCK 897 bool 898 899# 900# For architectures that want to enable the support for NUMA-affine scheduler 901# balancing logic: 902# 903config ARCH_SUPPORTS_NUMA_BALANCING 904 bool 905 906# 907# For architectures that know their GCC __int128 support is sound 908# 909config ARCH_SUPPORTS_INT128 910 bool 911 912# For architectures that (ab)use NUMA to represent different memory regions 913# all cpu-local but of different latencies, such as SuperH. 914# 915config ARCH_WANT_NUMA_VARIABLE_LOCALITY 916 bool 917 918config NUMA_BALANCING 919 bool "Memory placement aware NUMA scheduler" 920 depends on ARCH_SUPPORTS_NUMA_BALANCING 921 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 922 depends on SMP && NUMA && MIGRATION 923 help 924 This option adds support for automatic NUMA aware memory/task placement. 925 The mechanism is quite primitive and is based on migrating memory when 926 it has references to the node the task is running on. 927 928 This system will be inactive on UMA systems. 929 930config NUMA_BALANCING_DEFAULT_ENABLED 931 bool "Automatically enable NUMA aware memory/task placement" 932 default y 933 depends on NUMA_BALANCING 934 help 935 If set, automatic NUMA balancing will be enabled if running on a NUMA 936 machine. 937 938menuconfig CGROUPS 939 bool "Control Group support" 940 select KERNFS 941 help 942 This option adds support for grouping sets of processes together, for 943 use with process control subsystems such as Cpusets, CFS, memory 944 controls or device isolation. 945 See 946 - Documentation/scheduler/sched-design-CFS.txt (CFS) 947 - Documentation/cgroups/ (features for grouping, isolation 948 and resource control) 949 950 Say N if unsure. 951 952if CGROUPS 953 954config CGROUP_DEBUG 955 bool "Example debug cgroup subsystem" 956 default n 957 help 958 This option enables a simple cgroup subsystem that 959 exports useful debugging information about the cgroups 960 framework. 961 962 Say N if unsure. 963 964config CGROUP_FREEZER 965 bool "Freezer cgroup subsystem" 966 help 967 Provides a way to freeze and unfreeze all tasks in a 968 cgroup. 969 970config CGROUP_DEVICE 971 bool "Device controller for cgroups" 972 help 973 Provides a cgroup implementing whitelists for devices which 974 a process in the cgroup can mknod or open. 975 976config CPUSETS 977 bool "Cpuset support" 978 help 979 This option will let you create and manage CPUSETs which 980 allow dynamically partitioning a system into sets of CPUs and 981 Memory Nodes and assigning tasks to run only within those sets. 982 This is primarily useful on large SMP or NUMA systems. 983 984 Say N if unsure. 985 986config PROC_PID_CPUSET 987 bool "Include legacy /proc/<pid>/cpuset file" 988 depends on CPUSETS 989 default y 990 991config CGROUP_CPUACCT 992 bool "Simple CPU accounting cgroup subsystem" 993 help 994 Provides a simple Resource Controller for monitoring the 995 total CPU consumed by the tasks in a cgroup. 996 997config PAGE_COUNTER 998 bool 999 1000config MEMCG 1001 bool "Memory Resource Controller for Control Groups" 1002 select PAGE_COUNTER 1003 select EVENTFD 1004 help 1005 Provides a memory resource controller that manages both anonymous 1006 memory and page cache. (See Documentation/cgroups/memory.txt) 1007 1008config MEMCG_SWAP 1009 bool "Memory Resource Controller Swap Extension" 1010 depends on MEMCG && SWAP 1011 help 1012 Add swap management feature to memory resource controller. When you 1013 enable this, you can limit mem+swap usage per cgroup. In other words, 1014 when you disable this, memory resource controller has no cares to 1015 usage of swap...a process can exhaust all of the swap. This extension 1016 is useful when you want to avoid exhaustion swap but this itself 1017 adds more overheads and consumes memory for remembering information. 1018 Especially if you use 32bit system or small memory system, please 1019 be careful about enabling this. When memory resource controller 1020 is disabled by boot option, this will be automatically disabled and 1021 there will be no overhead from this. Even when you set this config=y, 1022 if boot option "swapaccount=0" is set, swap will not be accounted. 1023 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 1024 size is 4096bytes, 512k per 1Gbytes of swap. 1025config MEMCG_SWAP_ENABLED 1026 bool "Memory Resource Controller Swap Extension enabled by default" 1027 depends on MEMCG_SWAP 1028 default y 1029 help 1030 Memory Resource Controller Swap Extension comes with its price in 1031 a bigger memory consumption. General purpose distribution kernels 1032 which want to enable the feature but keep it disabled by default 1033 and let the user enable it by swapaccount=1 boot command line 1034 parameter should have this option unselected. 1035 For those who want to have the feature enabled by default should 1036 select this option (if, for some reason, they need to disable it 1037 then swapaccount=0 does the trick). 1038config MEMCG_KMEM 1039 bool "Memory Resource Controller Kernel Memory accounting" 1040 depends on MEMCG 1041 depends on SLUB || SLAB 1042 help 1043 The Kernel Memory extension for Memory Resource Controller can limit 1044 the amount of memory used by kernel objects in the system. Those are 1045 fundamentally different from the entities handled by the standard 1046 Memory Controller, which are page-based, and can be swapped. Users of 1047 the kmem extension can use it to guarantee that no group of processes 1048 will ever exhaust kernel resources alone. 1049 1050config CGROUP_HUGETLB 1051 bool "HugeTLB Resource Controller for Control Groups" 1052 depends on HUGETLB_PAGE 1053 select PAGE_COUNTER 1054 default n 1055 help 1056 Provides a cgroup Resource Controller for HugeTLB pages. 1057 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1058 The limit is enforced during page fault. Since HugeTLB doesn't 1059 support page reclaim, enforcing the limit at page fault time implies 1060 that, the application will get SIGBUS signal if it tries to access 1061 HugeTLB pages beyond its limit. This requires the application to know 1062 beforehand how much HugeTLB pages it would require for its use. The 1063 control group is tracked in the third page lru pointer. This means 1064 that we cannot use the controller with huge page less than 3 pages. 1065 1066config CGROUP_PERF 1067 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 1068 depends on PERF_EVENTS && CGROUPS 1069 help 1070 This option extends the per-cpu mode to restrict monitoring to 1071 threads which belong to the cgroup specified and run on the 1072 designated cpu. 1073 1074 Say N if unsure. 1075 1076menuconfig CGROUP_SCHED 1077 bool "Group CPU scheduler" 1078 default n 1079 help 1080 This feature lets CPU scheduler recognize task groups and control CPU 1081 bandwidth allocation to such task groups. It uses cgroups to group 1082 tasks. 1083 1084if CGROUP_SCHED 1085config FAIR_GROUP_SCHED 1086 bool "Group scheduling for SCHED_OTHER" 1087 depends on CGROUP_SCHED 1088 default CGROUP_SCHED 1089 1090config CFS_BANDWIDTH 1091 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1092 depends on FAIR_GROUP_SCHED 1093 default n 1094 help 1095 This option allows users to define CPU bandwidth rates (limits) for 1096 tasks running within the fair group scheduler. Groups with no limit 1097 set are considered to be unconstrained and will run with no 1098 restriction. 1099 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1100 1101config RT_GROUP_SCHED 1102 bool "Group scheduling for SCHED_RR/FIFO" 1103 depends on CGROUP_SCHED 1104 default n 1105 help 1106 This feature lets you explicitly allocate real CPU bandwidth 1107 to task groups. If enabled, it will also make it impossible to 1108 schedule realtime tasks for non-root users until you allocate 1109 realtime bandwidth for them. 1110 See Documentation/scheduler/sched-rt-group.txt for more information. 1111 1112endif #CGROUP_SCHED 1113 1114config BLK_CGROUP 1115 bool "Block IO controller" 1116 depends on BLOCK 1117 default n 1118 ---help--- 1119 Generic block IO controller cgroup interface. This is the common 1120 cgroup interface which should be used by various IO controlling 1121 policies. 1122 1123 Currently, CFQ IO scheduler uses it to recognize task groups and 1124 control disk bandwidth allocation (proportional time slice allocation) 1125 to such task groups. It is also used by bio throttling logic in 1126 block layer to implement upper limit in IO rates on a device. 1127 1128 This option only enables generic Block IO controller infrastructure. 1129 One needs to also enable actual IO controlling logic/policy. For 1130 enabling proportional weight division of disk bandwidth in CFQ, set 1131 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1132 CONFIG_BLK_DEV_THROTTLING=y. 1133 1134 See Documentation/cgroups/blkio-controller.txt for more information. 1135 1136config DEBUG_BLK_CGROUP 1137 bool "Enable Block IO controller debugging" 1138 depends on BLK_CGROUP 1139 default n 1140 ---help--- 1141 Enable some debugging help. Currently it exports additional stat 1142 files in a cgroup which can be useful for debugging. 1143 1144endif # CGROUPS 1145 1146config CHECKPOINT_RESTORE 1147 bool "Checkpoint/restore support" if EXPERT 1148 default n 1149 help 1150 Enables additional kernel features in a sake of checkpoint/restore. 1151 In particular it adds auxiliary prctl codes to setup process text, 1152 data and heap segment sizes, and a few additional /proc filesystem 1153 entries. 1154 1155 If unsure, say N here. 1156 1157menuconfig NAMESPACES 1158 bool "Namespaces support" if EXPERT 1159 depends on MULTIUSER 1160 default !EXPERT 1161 help 1162 Provides the way to make tasks work with different objects using 1163 the same id. For example same IPC id may refer to different objects 1164 or same user id or pid may refer to different tasks when used in 1165 different namespaces. 1166 1167if NAMESPACES 1168 1169config UTS_NS 1170 bool "UTS namespace" 1171 default y 1172 help 1173 In this namespace tasks see different info provided with the 1174 uname() system call 1175 1176config IPC_NS 1177 bool "IPC namespace" 1178 depends on (SYSVIPC || POSIX_MQUEUE) 1179 default y 1180 help 1181 In this namespace tasks work with IPC ids which correspond to 1182 different IPC objects in different namespaces. 1183 1184config USER_NS 1185 bool "User namespace" 1186 default n 1187 help 1188 This allows containers, i.e. vservers, to use user namespaces 1189 to provide different user info for different servers. 1190 1191 When user namespaces are enabled in the kernel it is 1192 recommended that the MEMCG and MEMCG_KMEM options also be 1193 enabled and that user-space use the memory control groups to 1194 limit the amount of memory a memory unprivileged users can 1195 use. 1196 1197 If unsure, say N. 1198 1199config PID_NS 1200 bool "PID Namespaces" 1201 default y 1202 help 1203 Support process id namespaces. This allows having multiple 1204 processes with the same pid as long as they are in different 1205 pid namespaces. This is a building block of containers. 1206 1207config NET_NS 1208 bool "Network namespace" 1209 depends on NET 1210 default y 1211 help 1212 Allow user space to create what appear to be multiple instances 1213 of the network stack. 1214 1215endif # NAMESPACES 1216 1217config SCHED_AUTOGROUP 1218 bool "Automatic process group scheduling" 1219 select CGROUPS 1220 select CGROUP_SCHED 1221 select FAIR_GROUP_SCHED 1222 help 1223 This option optimizes the scheduler for common desktop workloads by 1224 automatically creating and populating task groups. This separation 1225 of workloads isolates aggressive CPU burners (like build jobs) from 1226 desktop applications. Task group autogeneration is currently based 1227 upon task session. 1228 1229config SYSFS_DEPRECATED 1230 bool "Enable deprecated sysfs features to support old userspace tools" 1231 depends on SYSFS 1232 default n 1233 help 1234 This option adds code that switches the layout of the "block" class 1235 devices, to not show up in /sys/class/block/, but only in 1236 /sys/block/. 1237 1238 This switch is only active when the sysfs.deprecated=1 boot option is 1239 passed or the SYSFS_DEPRECATED_V2 option is set. 1240 1241 This option allows new kernels to run on old distributions and tools, 1242 which might get confused by /sys/class/block/. Since 2007/2008 all 1243 major distributions and tools handle this just fine. 1244 1245 Recent distributions and userspace tools after 2009/2010 depend on 1246 the existence of /sys/class/block/, and will not work with this 1247 option enabled. 1248 1249 Only if you are using a new kernel on an old distribution, you might 1250 need to say Y here. 1251 1252config SYSFS_DEPRECATED_V2 1253 bool "Enable deprecated sysfs features by default" 1254 default n 1255 depends on SYSFS 1256 depends on SYSFS_DEPRECATED 1257 help 1258 Enable deprecated sysfs by default. 1259 1260 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1261 option. 1262 1263 Only if you are using a new kernel on an old distribution, you might 1264 need to say Y here. Even then, odds are you would not need it 1265 enabled, you can always pass the boot option if absolutely necessary. 1266 1267config RELAY 1268 bool "Kernel->user space relay support (formerly relayfs)" 1269 help 1270 This option enables support for relay interface support in 1271 certain file systems (such as debugfs). 1272 It is designed to provide an efficient mechanism for tools and 1273 facilities to relay large amounts of data from kernel space to 1274 user space. 1275 1276 If unsure, say N. 1277 1278config BLK_DEV_INITRD 1279 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1280 depends on BROKEN || !FRV 1281 help 1282 The initial RAM filesystem is a ramfs which is loaded by the 1283 boot loader (loadlin or lilo) and that is mounted as root 1284 before the normal boot procedure. It is typically used to 1285 load modules needed to mount the "real" root file system, 1286 etc. See <file:Documentation/initrd.txt> for details. 1287 1288 If RAM disk support (BLK_DEV_RAM) is also included, this 1289 also enables initial RAM disk (initrd) support and adds 1290 15 Kbytes (more on some other architectures) to the kernel size. 1291 1292 If unsure say Y. 1293 1294if BLK_DEV_INITRD 1295 1296source "usr/Kconfig" 1297 1298endif 1299 1300config CC_OPTIMIZE_FOR_SIZE 1301 bool "Optimize for size" 1302 help 1303 Enabling this option will pass "-Os" instead of "-O2" to 1304 your compiler resulting in a smaller kernel. 1305 1306 If unsure, say N. 1307 1308config SYSCTL 1309 bool 1310 1311config ANON_INODES 1312 bool 1313 1314config HAVE_UID16 1315 bool 1316 1317config SYSCTL_EXCEPTION_TRACE 1318 bool 1319 help 1320 Enable support for /proc/sys/debug/exception-trace. 1321 1322config SYSCTL_ARCH_UNALIGN_NO_WARN 1323 bool 1324 help 1325 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1326 Allows arch to define/use @no_unaligned_warning to possibly warn 1327 about unaligned access emulation going on under the hood. 1328 1329config SYSCTL_ARCH_UNALIGN_ALLOW 1330 bool 1331 help 1332 Enable support for /proc/sys/kernel/unaligned-trap 1333 Allows arches to define/use @unaligned_enabled to runtime toggle 1334 the unaligned access emulation. 1335 see arch/parisc/kernel/unaligned.c for reference 1336 1337config HAVE_PCSPKR_PLATFORM 1338 bool 1339 1340# interpreter that classic socket filters depend on 1341config BPF 1342 bool 1343 1344menuconfig EXPERT 1345 bool "Configure standard kernel features (expert users)" 1346 # Unhide debug options, to make the on-by-default options visible 1347 select DEBUG_KERNEL 1348 help 1349 This option allows certain base kernel options and settings 1350 to be disabled or tweaked. This is for specialized 1351 environments which can tolerate a "non-standard" kernel. 1352 Only use this if you really know what you are doing. 1353 1354config UID16 1355 bool "Enable 16-bit UID system calls" if EXPERT 1356 depends on HAVE_UID16 && MULTIUSER 1357 default y 1358 help 1359 This enables the legacy 16-bit UID syscall wrappers. 1360 1361config MULTIUSER 1362 bool "Multiple users, groups and capabilities support" if EXPERT 1363 default y 1364 help 1365 This option enables support for non-root users, groups and 1366 capabilities. 1367 1368 If you say N here, all processes will run with UID 0, GID 0, and all 1369 possible capabilities. Saying N here also compiles out support for 1370 system calls related to UIDs, GIDs, and capabilities, such as setuid, 1371 setgid, and capset. 1372 1373 If unsure, say Y here. 1374 1375config SGETMASK_SYSCALL 1376 bool "sgetmask/ssetmask syscalls support" if EXPERT 1377 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1378 ---help--- 1379 sys_sgetmask and sys_ssetmask are obsolete system calls 1380 no longer supported in libc but still enabled by default in some 1381 architectures. 1382 1383 If unsure, leave the default option here. 1384 1385config SYSFS_SYSCALL 1386 bool "Sysfs syscall support" if EXPERT 1387 default y 1388 ---help--- 1389 sys_sysfs is an obsolete system call no longer supported in libc. 1390 Note that disabling this option is more secure but might break 1391 compatibility with some systems. 1392 1393 If unsure say Y here. 1394 1395config SYSCTL_SYSCALL 1396 bool "Sysctl syscall support" if EXPERT 1397 depends on PROC_SYSCTL 1398 default n 1399 select SYSCTL 1400 ---help--- 1401 sys_sysctl uses binary paths that have been found challenging 1402 to properly maintain and use. The interface in /proc/sys 1403 using paths with ascii names is now the primary path to this 1404 information. 1405 1406 Almost nothing using the binary sysctl interface so if you are 1407 trying to save some space it is probably safe to disable this, 1408 making your kernel marginally smaller. 1409 1410 If unsure say N here. 1411 1412config KALLSYMS 1413 bool "Load all symbols for debugging/ksymoops" if EXPERT 1414 default y 1415 help 1416 Say Y here to let the kernel print out symbolic crash information and 1417 symbolic stack backtraces. This increases the size of the kernel 1418 somewhat, as all symbols have to be loaded into the kernel image. 1419 1420config KALLSYMS_ALL 1421 bool "Include all symbols in kallsyms" 1422 depends on DEBUG_KERNEL && KALLSYMS 1423 help 1424 Normally kallsyms only contains the symbols of functions for nicer 1425 OOPS messages and backtraces (i.e., symbols from the text and inittext 1426 sections). This is sufficient for most cases. And only in very rare 1427 cases (e.g., when a debugger is used) all symbols are required (e.g., 1428 names of variables from the data sections, etc). 1429 1430 This option makes sure that all symbols are loaded into the kernel 1431 image (i.e., symbols from all sections) in cost of increased kernel 1432 size (depending on the kernel configuration, it may be 300KiB or 1433 something like this). 1434 1435 Say N unless you really need all symbols. 1436 1437config PRINTK 1438 default y 1439 bool "Enable support for printk" if EXPERT 1440 select IRQ_WORK 1441 help 1442 This option enables normal printk support. Removing it 1443 eliminates most of the message strings from the kernel image 1444 and makes the kernel more or less silent. As this makes it 1445 very difficult to diagnose system problems, saying N here is 1446 strongly discouraged. 1447 1448config BUG 1449 bool "BUG() support" if EXPERT 1450 default y 1451 help 1452 Disabling this option eliminates support for BUG and WARN, reducing 1453 the size of your kernel image and potentially quietly ignoring 1454 numerous fatal conditions. You should only consider disabling this 1455 option for embedded systems with no facilities for reporting errors. 1456 Just say Y. 1457 1458config ELF_CORE 1459 depends on COREDUMP 1460 default y 1461 bool "Enable ELF core dumps" if EXPERT 1462 help 1463 Enable support for generating core dumps. Disabling saves about 4k. 1464 1465 1466config PCSPKR_PLATFORM 1467 bool "Enable PC-Speaker support" if EXPERT 1468 depends on HAVE_PCSPKR_PLATFORM 1469 select I8253_LOCK 1470 default y 1471 help 1472 This option allows to disable the internal PC-Speaker 1473 support, saving some memory. 1474 1475config BASE_FULL 1476 default y 1477 bool "Enable full-sized data structures for core" if EXPERT 1478 help 1479 Disabling this option reduces the size of miscellaneous core 1480 kernel data structures. This saves memory on small machines, 1481 but may reduce performance. 1482 1483config FUTEX 1484 bool "Enable futex support" if EXPERT 1485 default y 1486 select RT_MUTEXES 1487 help 1488 Disabling this option will cause the kernel to be built without 1489 support for "fast userspace mutexes". The resulting kernel may not 1490 run glibc-based applications correctly. 1491 1492config HAVE_FUTEX_CMPXCHG 1493 bool 1494 depends on FUTEX 1495 help 1496 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1497 is implemented and always working. This removes a couple of runtime 1498 checks. 1499 1500config EPOLL 1501 bool "Enable eventpoll support" if EXPERT 1502 default y 1503 select ANON_INODES 1504 help 1505 Disabling this option will cause the kernel to be built without 1506 support for epoll family of system calls. 1507 1508config SIGNALFD 1509 bool "Enable signalfd() system call" if EXPERT 1510 select ANON_INODES 1511 default y 1512 help 1513 Enable the signalfd() system call that allows to receive signals 1514 on a file descriptor. 1515 1516 If unsure, say Y. 1517 1518config TIMERFD 1519 bool "Enable timerfd() system call" if EXPERT 1520 select ANON_INODES 1521 default y 1522 help 1523 Enable the timerfd() system call that allows to receive timer 1524 events on a file descriptor. 1525 1526 If unsure, say Y. 1527 1528config EVENTFD 1529 bool "Enable eventfd() system call" if EXPERT 1530 select ANON_INODES 1531 default y 1532 help 1533 Enable the eventfd() system call that allows to receive both 1534 kernel notification (ie. KAIO) or userspace notifications. 1535 1536 If unsure, say Y. 1537 1538# syscall, maps, verifier 1539config BPF_SYSCALL 1540 bool "Enable bpf() system call" 1541 select ANON_INODES 1542 select BPF 1543 default n 1544 help 1545 Enable the bpf() system call that allows to manipulate eBPF 1546 programs and maps via file descriptors. 1547 1548config SHMEM 1549 bool "Use full shmem filesystem" if EXPERT 1550 default y 1551 depends on MMU 1552 help 1553 The shmem is an internal filesystem used to manage shared memory. 1554 It is backed by swap and manages resource limits. It is also exported 1555 to userspace as tmpfs if TMPFS is enabled. Disabling this 1556 option replaces shmem and tmpfs with the much simpler ramfs code, 1557 which may be appropriate on small systems without swap. 1558 1559config AIO 1560 bool "Enable AIO support" if EXPERT 1561 default y 1562 help 1563 This option enables POSIX asynchronous I/O which may by used 1564 by some high performance threaded applications. Disabling 1565 this option saves about 7k. 1566 1567config ADVISE_SYSCALLS 1568 bool "Enable madvise/fadvise syscalls" if EXPERT 1569 default y 1570 help 1571 This option enables the madvise and fadvise syscalls, used by 1572 applications to advise the kernel about their future memory or file 1573 usage, improving performance. If building an embedded system where no 1574 applications use these syscalls, you can disable this option to save 1575 space. 1576 1577config PCI_QUIRKS 1578 default y 1579 bool "Enable PCI quirk workarounds" if EXPERT 1580 depends on PCI 1581 help 1582 This enables workarounds for various PCI chipset 1583 bugs/quirks. Disable this only if your target machine is 1584 unaffected by PCI quirks. 1585 1586config EMBEDDED 1587 bool "Embedded system" 1588 option allnoconfig_y 1589 select EXPERT 1590 help 1591 This option should be enabled if compiling the kernel for 1592 an embedded system so certain expert options are available 1593 for configuration. 1594 1595config HAVE_PERF_EVENTS 1596 bool 1597 help 1598 See tools/perf/design.txt for details. 1599 1600config PERF_USE_VMALLOC 1601 bool 1602 help 1603 See tools/perf/design.txt for details 1604 1605menu "Kernel Performance Events And Counters" 1606 1607config PERF_EVENTS 1608 bool "Kernel performance events and counters" 1609 default y if PROFILING 1610 depends on HAVE_PERF_EVENTS 1611 select ANON_INODES 1612 select IRQ_WORK 1613 select SRCU 1614 help 1615 Enable kernel support for various performance events provided 1616 by software and hardware. 1617 1618 Software events are supported either built-in or via the 1619 use of generic tracepoints. 1620 1621 Most modern CPUs support performance events via performance 1622 counter registers. These registers count the number of certain 1623 types of hw events: such as instructions executed, cachemisses 1624 suffered, or branches mis-predicted - without slowing down the 1625 kernel or applications. These registers can also trigger interrupts 1626 when a threshold number of events have passed - and can thus be 1627 used to profile the code that runs on that CPU. 1628 1629 The Linux Performance Event subsystem provides an abstraction of 1630 these software and hardware event capabilities, available via a 1631 system call and used by the "perf" utility in tools/perf/. It 1632 provides per task and per CPU counters, and it provides event 1633 capabilities on top of those. 1634 1635 Say Y if unsure. 1636 1637config DEBUG_PERF_USE_VMALLOC 1638 default n 1639 bool "Debug: use vmalloc to back perf mmap() buffers" 1640 depends on PERF_EVENTS && DEBUG_KERNEL 1641 select PERF_USE_VMALLOC 1642 help 1643 Use vmalloc memory to back perf mmap() buffers. 1644 1645 Mostly useful for debugging the vmalloc code on platforms 1646 that don't require it. 1647 1648 Say N if unsure. 1649 1650endmenu 1651 1652config VM_EVENT_COUNTERS 1653 default y 1654 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1655 help 1656 VM event counters are needed for event counts to be shown. 1657 This option allows the disabling of the VM event counters 1658 on EXPERT systems. /proc/vmstat will only show page counts 1659 if VM event counters are disabled. 1660 1661config SLUB_DEBUG 1662 default y 1663 bool "Enable SLUB debugging support" if EXPERT 1664 depends on SLUB && SYSFS 1665 help 1666 SLUB has extensive debug support features. Disabling these can 1667 result in significant savings in code size. This also disables 1668 SLUB sysfs support. /sys/slab will not exist and there will be 1669 no support for cache validation etc. 1670 1671config COMPAT_BRK 1672 bool "Disable heap randomization" 1673 default y 1674 help 1675 Randomizing heap placement makes heap exploits harder, but it 1676 also breaks ancient binaries (including anything libc5 based). 1677 This option changes the bootup default to heap randomization 1678 disabled, and can be overridden at runtime by setting 1679 /proc/sys/kernel/randomize_va_space to 2. 1680 1681 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1682 1683choice 1684 prompt "Choose SLAB allocator" 1685 default SLUB 1686 help 1687 This option allows to select a slab allocator. 1688 1689config SLAB 1690 bool "SLAB" 1691 help 1692 The regular slab allocator that is established and known to work 1693 well in all environments. It organizes cache hot objects in 1694 per cpu and per node queues. 1695 1696config SLUB 1697 bool "SLUB (Unqueued Allocator)" 1698 help 1699 SLUB is a slab allocator that minimizes cache line usage 1700 instead of managing queues of cached objects (SLAB approach). 1701 Per cpu caching is realized using slabs of objects instead 1702 of queues of objects. SLUB can use memory efficiently 1703 and has enhanced diagnostics. SLUB is the default choice for 1704 a slab allocator. 1705 1706config SLOB 1707 depends on EXPERT 1708 bool "SLOB (Simple Allocator)" 1709 help 1710 SLOB replaces the stock allocator with a drastically simpler 1711 allocator. SLOB is generally more space efficient but 1712 does not perform as well on large systems. 1713 1714endchoice 1715 1716config SLUB_CPU_PARTIAL 1717 default y 1718 depends on SLUB && SMP 1719 bool "SLUB per cpu partial cache" 1720 help 1721 Per cpu partial caches accellerate objects allocation and freeing 1722 that is local to a processor at the price of more indeterminism 1723 in the latency of the free. On overflow these caches will be cleared 1724 which requires the taking of locks that may cause latency spikes. 1725 Typically one would choose no for a realtime system. 1726 1727config MMAP_ALLOW_UNINITIALIZED 1728 bool "Allow mmapped anonymous memory to be uninitialized" 1729 depends on EXPERT && !MMU 1730 default n 1731 help 1732 Normally, and according to the Linux spec, anonymous memory obtained 1733 from mmap() has it's contents cleared before it is passed to 1734 userspace. Enabling this config option allows you to request that 1735 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1736 providing a huge performance boost. If this option is not enabled, 1737 then the flag will be ignored. 1738 1739 This is taken advantage of by uClibc's malloc(), and also by 1740 ELF-FDPIC binfmt's brk and stack allocator. 1741 1742 Because of the obvious security issues, this option should only be 1743 enabled on embedded devices where you control what is run in 1744 userspace. Since that isn't generally a problem on no-MMU systems, 1745 it is normally safe to say Y here. 1746 1747 See Documentation/nommu-mmap.txt for more information. 1748 1749config SYSTEM_TRUSTED_KEYRING 1750 bool "Provide system-wide ring of trusted keys" 1751 depends on KEYS 1752 help 1753 Provide a system keyring to which trusted keys can be added. Keys in 1754 the keyring are considered to be trusted. Keys may be added at will 1755 by the kernel from compiled-in data and from hardware key stores, but 1756 userspace may only add extra keys if those keys can be verified by 1757 keys already in the keyring. 1758 1759 Keys in this keyring are used by module signature checking. 1760 1761config PROFILING 1762 bool "Profiling support" 1763 help 1764 Say Y here to enable the extended profiling support mechanisms used 1765 by profilers such as OProfile. 1766 1767# 1768# Place an empty function call at each tracepoint site. Can be 1769# dynamically changed for a probe function. 1770# 1771config TRACEPOINTS 1772 bool 1773 1774source "arch/Kconfig" 1775 1776endmenu # General setup 1777 1778config HAVE_GENERIC_DMA_COHERENT 1779 bool 1780 default n 1781 1782config SLABINFO 1783 bool 1784 depends on PROC_FS 1785 depends on SLAB || SLUB_DEBUG 1786 default y 1787 1788config RT_MUTEXES 1789 bool 1790 1791config BASE_SMALL 1792 int 1793 default 0 if BASE_FULL 1794 default 1 if !BASE_FULL 1795 1796menuconfig MODULES 1797 bool "Enable loadable module support" 1798 option modules 1799 help 1800 Kernel modules are small pieces of compiled code which can 1801 be inserted in the running kernel, rather than being 1802 permanently built into the kernel. You use the "modprobe" 1803 tool to add (and sometimes remove) them. If you say Y here, 1804 many parts of the kernel can be built as modules (by 1805 answering M instead of Y where indicated): this is most 1806 useful for infrequently used options which are not required 1807 for booting. For more information, see the man pages for 1808 modprobe, lsmod, modinfo, insmod and rmmod. 1809 1810 If you say Y here, you will need to run "make 1811 modules_install" to put the modules under /lib/modules/ 1812 where modprobe can find them (you may need to be root to do 1813 this). 1814 1815 If unsure, say Y. 1816 1817if MODULES 1818 1819config MODULE_FORCE_LOAD 1820 bool "Forced module loading" 1821 default n 1822 help 1823 Allow loading of modules without version information (ie. modprobe 1824 --force). Forced module loading sets the 'F' (forced) taint flag and 1825 is usually a really bad idea. 1826 1827config MODULE_UNLOAD 1828 bool "Module unloading" 1829 help 1830 Without this option you will not be able to unload any 1831 modules (note that some modules may not be unloadable 1832 anyway), which makes your kernel smaller, faster 1833 and simpler. If unsure, say Y. 1834 1835config MODULE_FORCE_UNLOAD 1836 bool "Forced module unloading" 1837 depends on MODULE_UNLOAD 1838 help 1839 This option allows you to force a module to unload, even if the 1840 kernel believes it is unsafe: the kernel will remove the module 1841 without waiting for anyone to stop using it (using the -f option to 1842 rmmod). This is mainly for kernel developers and desperate users. 1843 If unsure, say N. 1844 1845config MODVERSIONS 1846 bool "Module versioning support" 1847 help 1848 Usually, you have to use modules compiled with your kernel. 1849 Saying Y here makes it sometimes possible to use modules 1850 compiled for different kernels, by adding enough information 1851 to the modules to (hopefully) spot any changes which would 1852 make them incompatible with the kernel you are running. If 1853 unsure, say N. 1854 1855config MODULE_SRCVERSION_ALL 1856 bool "Source checksum for all modules" 1857 help 1858 Modules which contain a MODULE_VERSION get an extra "srcversion" 1859 field inserted into their modinfo section, which contains a 1860 sum of the source files which made it. This helps maintainers 1861 see exactly which source was used to build a module (since 1862 others sometimes change the module source without updating 1863 the version). With this option, such a "srcversion" field 1864 will be created for all modules. If unsure, say N. 1865 1866config MODULE_SIG 1867 bool "Module signature verification" 1868 depends on MODULES 1869 select SYSTEM_TRUSTED_KEYRING 1870 select KEYS 1871 select CRYPTO 1872 select ASYMMETRIC_KEY_TYPE 1873 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1874 select PUBLIC_KEY_ALGO_RSA 1875 select ASN1 1876 select OID_REGISTRY 1877 select X509_CERTIFICATE_PARSER 1878 help 1879 Check modules for valid signatures upon load: the signature 1880 is simply appended to the module. For more information see 1881 Documentation/module-signing.txt. 1882 1883 !!!WARNING!!! If you enable this option, you MUST make sure that the 1884 module DOES NOT get stripped after being signed. This includes the 1885 debuginfo strip done by some packagers (such as rpmbuild) and 1886 inclusion into an initramfs that wants the module size reduced. 1887 1888config MODULE_SIG_FORCE 1889 bool "Require modules to be validly signed" 1890 depends on MODULE_SIG 1891 help 1892 Reject unsigned modules or signed modules for which we don't have a 1893 key. Without this, such modules will simply taint the kernel. 1894 1895config MODULE_SIG_ALL 1896 bool "Automatically sign all modules" 1897 default y 1898 depends on MODULE_SIG 1899 help 1900 Sign all modules during make modules_install. Without this option, 1901 modules must be signed manually, using the scripts/sign-file tool. 1902 1903comment "Do not forget to sign required modules with scripts/sign-file" 1904 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1905 1906choice 1907 prompt "Which hash algorithm should modules be signed with?" 1908 depends on MODULE_SIG 1909 help 1910 This determines which sort of hashing algorithm will be used during 1911 signature generation. This algorithm _must_ be built into the kernel 1912 directly so that signature verification can take place. It is not 1913 possible to load a signed module containing the algorithm to check 1914 the signature on that module. 1915 1916config MODULE_SIG_SHA1 1917 bool "Sign modules with SHA-1" 1918 select CRYPTO_SHA1 1919 1920config MODULE_SIG_SHA224 1921 bool "Sign modules with SHA-224" 1922 select CRYPTO_SHA256 1923 1924config MODULE_SIG_SHA256 1925 bool "Sign modules with SHA-256" 1926 select CRYPTO_SHA256 1927 1928config MODULE_SIG_SHA384 1929 bool "Sign modules with SHA-384" 1930 select CRYPTO_SHA512 1931 1932config MODULE_SIG_SHA512 1933 bool "Sign modules with SHA-512" 1934 select CRYPTO_SHA512 1935 1936endchoice 1937 1938config MODULE_SIG_HASH 1939 string 1940 depends on MODULE_SIG 1941 default "sha1" if MODULE_SIG_SHA1 1942 default "sha224" if MODULE_SIG_SHA224 1943 default "sha256" if MODULE_SIG_SHA256 1944 default "sha384" if MODULE_SIG_SHA384 1945 default "sha512" if MODULE_SIG_SHA512 1946 1947config MODULE_COMPRESS 1948 bool "Compress modules on installation" 1949 depends on MODULES 1950 help 1951 This option compresses the kernel modules when 'make 1952 modules_install' is run. 1953 1954 The modules will be compressed either using gzip or xz depend on the 1955 choice made in "Compression algorithm". 1956 1957 module-init-tools has support for gzip format while kmod handle gzip 1958 and xz compressed modules. 1959 1960 When a kernel module is installed from outside of the main kernel 1961 source and uses the Kbuild system for installing modules then that 1962 kernel module will also be compressed when it is installed. 1963 1964 This option provides little benefit when the modules are to be used inside 1965 an initrd or initramfs, it generally is more efficient to compress the whole 1966 initrd or initramfs instead. 1967 1968 This is fully compatible with signed modules while the signed module is 1969 compressed. module-init-tools or kmod handles decompression and provide to 1970 other layer the uncompressed but signed payload. 1971 1972choice 1973 prompt "Compression algorithm" 1974 depends on MODULE_COMPRESS 1975 default MODULE_COMPRESS_GZIP 1976 help 1977 This determines which sort of compression will be used during 1978 'make modules_install'. 1979 1980 GZIP (default) and XZ are supported. 1981 1982config MODULE_COMPRESS_GZIP 1983 bool "GZIP" 1984 1985config MODULE_COMPRESS_XZ 1986 bool "XZ" 1987 1988endchoice 1989 1990endif # MODULES 1991 1992config INIT_ALL_POSSIBLE 1993 bool 1994 help 1995 Back when each arch used to define their own cpu_online_mask and 1996 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1997 with all 1s, and others with all 0s. When they were centralised, 1998 it was better to provide this option than to break all the archs 1999 and have several arch maintainers pursuing me down dark alleys. 2000 2001config STOP_MACHINE 2002 bool 2003 default y 2004 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 2005 help 2006 Need stop_machine() primitive. 2007 2008source "block/Kconfig" 2009 2010config PREEMPT_NOTIFIERS 2011 bool 2012 2013config PADATA 2014 depends on SMP 2015 bool 2016 2017# Can be selected by architectures with broken toolchains 2018# that get confused by correct const<->read_only section 2019# mappings 2020config BROKEN_RODATA 2021 bool 2022 2023config ASN1 2024 tristate 2025 help 2026 Build a simple ASN.1 grammar compiler that produces a bytecode output 2027 that can be interpreted by the ASN.1 stream decoder and used to 2028 inform it as to what tags are to be expected in a stream and what 2029 functions to call on what tags. 2030 2031source "kernel/Kconfig.locks" 2032