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 help 398 If you say Y here, a user level program will be able to instruct the 399 kernel (via a special system call) to write process accounting 400 information to a file: whenever a process exits, information about 401 that process will be appended to the file by the kernel. The 402 information includes things such as creation time, owning user, 403 command name, memory usage, controlling terminal etc. (the complete 404 list is in the struct acct in <file:include/linux/acct.h>). It is 405 up to the user level program to do useful things with this 406 information. This is generally a good idea, so say Y. 407 408config BSD_PROCESS_ACCT_V3 409 bool "BSD Process Accounting version 3 file format" 410 depends on BSD_PROCESS_ACCT 411 default n 412 help 413 If you say Y here, the process accounting information is written 414 in a new file format that also logs the process IDs of each 415 process and it's parent. Note that this file format is incompatible 416 with previous v0/v1/v2 file formats, so you will need updated tools 417 for processing it. A preliminary version of these tools is available 418 at <http://www.gnu.org/software/acct/>. 419 420config TASKSTATS 421 bool "Export task/process statistics through netlink" 422 depends on NET 423 default n 424 help 425 Export selected statistics for tasks/processes through the 426 generic netlink interface. Unlike BSD process accounting, the 427 statistics are available during the lifetime of tasks/processes as 428 responses to commands. Like BSD accounting, they are sent to user 429 space on task exit. 430 431 Say N if unsure. 432 433config TASK_DELAY_ACCT 434 bool "Enable per-task delay accounting" 435 depends on TASKSTATS 436 help 437 Collect information on time spent by a task waiting for system 438 resources like cpu, synchronous block I/O completion and swapping 439 in pages. Such statistics can help in setting a task's priorities 440 relative to other tasks for cpu, io, rss limits etc. 441 442 Say N if unsure. 443 444config TASK_XACCT 445 bool "Enable extended accounting over taskstats" 446 depends on TASKSTATS 447 help 448 Collect extended task accounting data and send the data 449 to userland for processing over the taskstats interface. 450 451 Say N if unsure. 452 453config TASK_IO_ACCOUNTING 454 bool "Enable per-task storage I/O accounting" 455 depends on TASK_XACCT 456 help 457 Collect information on the number of bytes of storage I/O which this 458 task has caused. 459 460 Say N if unsure. 461 462endmenu # "CPU/Task time and stats accounting" 463 464menu "RCU Subsystem" 465 466choice 467 prompt "RCU Implementation" 468 default TREE_RCU 469 470config TREE_RCU 471 bool "Tree-based hierarchical RCU" 472 depends on !PREEMPT && SMP 473 select IRQ_WORK 474 help 475 This option selects the RCU implementation that is 476 designed for very large SMP system with hundreds or 477 thousands of CPUs. It also scales down nicely to 478 smaller systems. 479 480config TREE_PREEMPT_RCU 481 bool "Preemptible tree-based hierarchical RCU" 482 depends on PREEMPT 483 select IRQ_WORK 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 PREEMPT_RCU 505 def_bool TREE_PREEMPT_RCU 506 help 507 This option enables preemptible-RCU code that is common between 508 TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU. 509 510config RCU_STALL_COMMON 511 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE ) 512 help 513 This option enables RCU CPU stall code that is common between 514 the TINY and TREE variants of RCU. The purpose is to allow 515 the tiny variants to disable RCU CPU stall warnings, while 516 making these warnings mandatory for the tree variants. 517 518config CONTEXT_TRACKING 519 bool 520 521config RCU_USER_QS 522 bool "Consider userspace as in RCU extended quiescent state" 523 depends on HAVE_CONTEXT_TRACKING && SMP 524 select CONTEXT_TRACKING 525 help 526 This option sets hooks on kernel / userspace boundaries and 527 puts RCU in extended quiescent state when the CPU runs in 528 userspace. It means that when a CPU runs in userspace, it is 529 excluded from the global RCU state machine and thus doesn't 530 try to keep the timer tick on for RCU. 531 532 Unless you want to hack and help the development of the full 533 dynticks mode, you shouldn't enable this option. It also 534 adds unnecessary overhead. 535 536 If unsure say N 537 538config CONTEXT_TRACKING_FORCE 539 bool "Force context tracking" 540 depends on CONTEXT_TRACKING 541 default y if !NO_HZ_FULL 542 help 543 The major pre-requirement for full dynticks to work is to 544 support the context tracking subsystem. But there are also 545 other dependencies to provide in order to make the full 546 dynticks working. 547 548 This option stands for testing when an arch implements the 549 context tracking backend but doesn't yet fullfill all the 550 requirements to make the full dynticks feature working. 551 Without the full dynticks, there is no way to test the support 552 for context tracking and the subsystems that rely on it: RCU 553 userspace extended quiescent state and tickless cputime 554 accounting. This option copes with the absence of the full 555 dynticks subsystem by forcing the context tracking on all 556 CPUs in the system. 557 558 Say Y only if you're working on the development of an 559 architecture backend for the context tracking. 560 561 Say N otherwise, this option brings an overhead that you 562 don't want in production. 563 564 565config RCU_FANOUT 566 int "Tree-based hierarchical RCU fanout value" 567 range 2 64 if 64BIT 568 range 2 32 if !64BIT 569 depends on TREE_RCU || TREE_PREEMPT_RCU 570 default 64 if 64BIT 571 default 32 if !64BIT 572 help 573 This option controls the fanout of hierarchical implementations 574 of RCU, allowing RCU to work efficiently on machines with 575 large numbers of CPUs. This value must be at least the fourth 576 root of NR_CPUS, which allows NR_CPUS to be insanely large. 577 The default value of RCU_FANOUT should be used for production 578 systems, but if you are stress-testing the RCU implementation 579 itself, small RCU_FANOUT values allow you to test large-system 580 code paths on small(er) systems. 581 582 Select a specific number if testing RCU itself. 583 Take the default if unsure. 584 585config RCU_FANOUT_LEAF 586 int "Tree-based hierarchical RCU leaf-level fanout value" 587 range 2 RCU_FANOUT if 64BIT 588 range 2 RCU_FANOUT if !64BIT 589 depends on TREE_RCU || TREE_PREEMPT_RCU 590 default 16 591 help 592 This option controls the leaf-level fanout of hierarchical 593 implementations of RCU, and allows trading off cache misses 594 against lock contention. Systems that synchronize their 595 scheduling-clock interrupts for energy-efficiency reasons will 596 want the default because the smaller leaf-level fanout keeps 597 lock contention levels acceptably low. Very large systems 598 (hundreds or thousands of CPUs) will instead want to set this 599 value to the maximum value possible in order to reduce the 600 number of cache misses incurred during RCU's grace-period 601 initialization. These systems tend to run CPU-bound, and thus 602 are not helped by synchronized interrupts, and thus tend to 603 skew them, which reduces lock contention enough that large 604 leaf-level fanouts work well. 605 606 Select a specific number if testing RCU itself. 607 608 Select the maximum permissible value for large systems. 609 610 Take the default if unsure. 611 612config RCU_FANOUT_EXACT 613 bool "Disable tree-based hierarchical RCU auto-balancing" 614 depends on TREE_RCU || TREE_PREEMPT_RCU 615 default n 616 help 617 This option forces use of the exact RCU_FANOUT value specified, 618 regardless of imbalances in the hierarchy. This is useful for 619 testing RCU itself, and might one day be useful on systems with 620 strong NUMA behavior. 621 622 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 623 624 Say N if unsure. 625 626config RCU_FAST_NO_HZ 627 bool "Accelerate last non-dyntick-idle CPU's grace periods" 628 depends on NO_HZ_COMMON && SMP 629 default n 630 help 631 This option permits CPUs to enter dynticks-idle state even if 632 they have RCU callbacks queued, and prevents RCU from waking 633 these CPUs up more than roughly once every four jiffies (by 634 default, you can adjust this using the rcutree.rcu_idle_gp_delay 635 parameter), thus improving energy efficiency. On the other 636 hand, this option increases the duration of RCU grace periods, 637 for example, slowing down synchronize_rcu(). 638 639 Say Y if energy efficiency is critically important, and you 640 don't care about increased grace-period durations. 641 642 Say N if you are unsure. 643 644config TREE_RCU_TRACE 645 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 646 select DEBUG_FS 647 help 648 This option provides tracing for the TREE_RCU and 649 TREE_PREEMPT_RCU implementations, permitting Makefile to 650 trivially select kernel/rcutree_trace.c. 651 652config RCU_BOOST 653 bool "Enable RCU priority boosting" 654 depends on RT_MUTEXES && PREEMPT_RCU 655 default n 656 help 657 This option boosts the priority of preempted RCU readers that 658 block the current preemptible RCU grace period for too long. 659 This option also prevents heavy loads from blocking RCU 660 callback invocation for all flavors of RCU. 661 662 Say Y here if you are working with real-time apps or heavy loads 663 Say N here if you are unsure. 664 665config RCU_BOOST_PRIO 666 int "Real-time priority to boost RCU readers to" 667 range 1 99 668 depends on RCU_BOOST 669 default 1 670 help 671 This option specifies the real-time priority to which long-term 672 preempted RCU readers are to be boosted. If you are working 673 with a real-time application that has one or more CPU-bound 674 threads running at a real-time priority level, you should set 675 RCU_BOOST_PRIO to a priority higher then the highest-priority 676 real-time CPU-bound thread. The default RCU_BOOST_PRIO value 677 of 1 is appropriate in the common case, which is real-time 678 applications that do not have any CPU-bound threads. 679 680 Some real-time applications might not have a single real-time 681 thread that saturates a given CPU, but instead might have 682 multiple real-time threads that, taken together, fully utilize 683 that CPU. In this case, you should set RCU_BOOST_PRIO to 684 a priority higher than the lowest-priority thread that is 685 conspiring to prevent the CPU from running any non-real-time 686 tasks. For example, if one thread at priority 10 and another 687 thread at priority 5 are between themselves fully consuming 688 the CPU time on a given CPU, then RCU_BOOST_PRIO should be 689 set to priority 6 or higher. 690 691 Specify the real-time priority, or take the default if unsure. 692 693config RCU_BOOST_DELAY 694 int "Milliseconds to delay boosting after RCU grace-period start" 695 range 0 3000 696 depends on RCU_BOOST 697 default 500 698 help 699 This option specifies the time to wait after the beginning of 700 a given grace period before priority-boosting preempted RCU 701 readers blocking that grace period. Note that any RCU reader 702 blocking an expedited RCU grace period is boosted immediately. 703 704 Accept the default if unsure. 705 706config RCU_NOCB_CPU 707 bool "Offload RCU callback processing from boot-selected CPUs" 708 depends on TREE_RCU || TREE_PREEMPT_RCU 709 default n 710 help 711 Use this option to reduce OS jitter for aggressive HPC or 712 real-time workloads. It can also be used to offload RCU 713 callback invocation to energy-efficient CPUs in battery-powered 714 asymmetric multiprocessors. 715 716 This option offloads callback invocation from the set of 717 CPUs specified at boot time by the rcu_nocbs parameter. 718 For each such CPU, a kthread ("rcuox/N") will be created to 719 invoke callbacks, where the "N" is the CPU being offloaded, 720 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 721 "s" for RCU-sched. Nothing prevents this kthread from running 722 on the specified CPUs, but (1) the kthreads may be preempted 723 between each callback, and (2) affinity or cgroups can be used 724 to force the kthreads to run on whatever set of CPUs is desired. 725 726 Say Y here if you want to help to debug reduced OS jitter. 727 Say N here if you are unsure. 728 729choice 730 prompt "Build-forced no-CBs CPUs" 731 default RCU_NOCB_CPU_NONE 732 help 733 This option allows no-CBs CPUs (whose RCU callbacks are invoked 734 from kthreads rather than from softirq context) to be specified 735 at build time. Additional no-CBs CPUs may be specified by 736 the rcu_nocbs= boot parameter. 737 738config RCU_NOCB_CPU_NONE 739 bool "No build_forced no-CBs CPUs" 740 depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL 741 help 742 This option does not force any of the CPUs to be no-CBs CPUs. 743 Only CPUs designated by the rcu_nocbs= boot parameter will be 744 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 745 kthreads whose names begin with "rcuo". All other CPUs will 746 invoke their own RCU callbacks in softirq context. 747 748 Select this option if you want to choose no-CBs CPUs at 749 boot time, for example, to allow testing of different no-CBs 750 configurations without having to rebuild the kernel each time. 751 752config RCU_NOCB_CPU_ZERO 753 bool "CPU 0 is a build_forced no-CBs CPU" 754 depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL 755 help 756 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 757 callbacks are invoked by a per-CPU kthread whose name begins 758 with "rcuo". Additional CPUs may be designated as no-CBs 759 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 760 All other CPUs will invoke their own RCU callbacks in softirq 761 context. 762 763 Select this if CPU 0 needs to be a no-CBs CPU for real-time 764 or energy-efficiency reasons, but the real reason it exists 765 is to ensure that randconfig testing covers mixed systems. 766 767config RCU_NOCB_CPU_ALL 768 bool "All CPUs are build_forced no-CBs CPUs" 769 depends on RCU_NOCB_CPU 770 help 771 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 772 boot parameter will be ignored. All CPUs' RCU callbacks will 773 be executed in the context of per-CPU rcuo kthreads created for 774 this purpose. Assuming that the kthreads whose names start with 775 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 776 on the remaining CPUs, but might decrease memory locality during 777 RCU-callback invocation, thus potentially degrading throughput. 778 779 Select this if all CPUs need to be no-CBs CPUs for real-time 780 or energy-efficiency reasons. 781 782endchoice 783 784endmenu # "RCU Subsystem" 785 786config BUILD_BIN2C 787 bool 788 default n 789 790config IKCONFIG 791 tristate "Kernel .config support" 792 select BUILD_BIN2C 793 ---help--- 794 This option enables the complete Linux kernel ".config" file 795 contents to be saved in the kernel. It provides documentation 796 of which kernel options are used in a running kernel or in an 797 on-disk kernel. This information can be extracted from the kernel 798 image file with the script scripts/extract-ikconfig and used as 799 input to rebuild the current kernel or to build another kernel. 800 It can also be extracted from a running kernel by reading 801 /proc/config.gz if enabled (below). 802 803config IKCONFIG_PROC 804 bool "Enable access to .config through /proc/config.gz" 805 depends on IKCONFIG && PROC_FS 806 ---help--- 807 This option enables access to the kernel configuration file 808 through /proc/config.gz. 809 810config LOG_BUF_SHIFT 811 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 812 range 12 21 813 default 17 814 depends on PRINTK 815 help 816 Select the minimal kernel log buffer size as a power of 2. 817 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config 818 parameter, see below. Any higher size also might be forced 819 by "log_buf_len" boot parameter. 820 821 Examples: 822 17 => 128 KB 823 16 => 64 KB 824 15 => 32 KB 825 14 => 16 KB 826 13 => 8 KB 827 12 => 4 KB 828 829config LOG_CPU_MAX_BUF_SHIFT 830 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" 831 range 0 21 832 default 12 if !BASE_SMALL 833 default 0 if BASE_SMALL 834 depends on PRINTK 835 help 836 This option allows to increase the default ring buffer size 837 according to the number of CPUs. The value defines the contribution 838 of each CPU as a power of 2. The used space is typically only few 839 lines however it might be much more when problems are reported, 840 e.g. backtraces. 841 842 The increased size means that a new buffer has to be allocated and 843 the original static one is unused. It makes sense only on systems 844 with more CPUs. Therefore this value is used only when the sum of 845 contributions is greater than the half of the default kernel ring 846 buffer as defined by LOG_BUF_SHIFT. The default values are set 847 so that more than 64 CPUs are needed to trigger the allocation. 848 849 Also this option is ignored when "log_buf_len" kernel parameter is 850 used as it forces an exact (power of two) size of the ring buffer. 851 852 The number of possible CPUs is used for this computation ignoring 853 hotplugging making the compuation optimal for the the worst case 854 scenerio while allowing a simple algorithm to be used from bootup. 855 856 Examples shift values and their meaning: 857 17 => 128 KB for each CPU 858 16 => 64 KB for each CPU 859 15 => 32 KB for each CPU 860 14 => 16 KB for each CPU 861 13 => 8 KB for each CPU 862 12 => 4 KB for each CPU 863 864# 865# Architectures with an unreliable sched_clock() should select this: 866# 867config HAVE_UNSTABLE_SCHED_CLOCK 868 bool 869 870config GENERIC_SCHED_CLOCK 871 bool 872 873# 874# For architectures that want to enable the support for NUMA-affine scheduler 875# balancing logic: 876# 877config ARCH_SUPPORTS_NUMA_BALANCING 878 bool 879 880# 881# For architectures that know their GCC __int128 support is sound 882# 883config ARCH_SUPPORTS_INT128 884 bool 885 886# For architectures that (ab)use NUMA to represent different memory regions 887# all cpu-local but of different latencies, such as SuperH. 888# 889config ARCH_WANT_NUMA_VARIABLE_LOCALITY 890 bool 891 892# 893# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE 894config ARCH_WANTS_PROT_NUMA_PROT_NONE 895 bool 896 897config ARCH_USES_NUMA_PROT_NONE 898 bool 899 default y 900 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE 901 depends on NUMA_BALANCING 902 903config NUMA_BALANCING_DEFAULT_ENABLED 904 bool "Automatically enable NUMA aware memory/task placement" 905 default y 906 depends on NUMA_BALANCING 907 help 908 If set, automatic NUMA balancing will be enabled if running on a NUMA 909 machine. 910 911config NUMA_BALANCING 912 bool "Memory placement aware NUMA scheduler" 913 depends on ARCH_SUPPORTS_NUMA_BALANCING 914 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 915 depends on SMP && NUMA && MIGRATION 916 help 917 This option adds support for automatic NUMA aware memory/task placement. 918 The mechanism is quite primitive and is based on migrating memory when 919 it has references to the node the task is running on. 920 921 This system will be inactive on UMA systems. 922 923menuconfig CGROUPS 924 boolean "Control Group support" 925 select KERNFS 926 help 927 This option adds support for grouping sets of processes together, for 928 use with process control subsystems such as Cpusets, CFS, memory 929 controls or device isolation. 930 See 931 - Documentation/scheduler/sched-design-CFS.txt (CFS) 932 - Documentation/cgroups/ (features for grouping, isolation 933 and resource control) 934 935 Say N if unsure. 936 937if CGROUPS 938 939config CGROUP_DEBUG 940 bool "Example debug cgroup subsystem" 941 default n 942 help 943 This option enables a simple cgroup subsystem that 944 exports useful debugging information about the cgroups 945 framework. 946 947 Say N if unsure. 948 949config CGROUP_FREEZER 950 bool "Freezer cgroup subsystem" 951 help 952 Provides a way to freeze and unfreeze all tasks in a 953 cgroup. 954 955config CGROUP_DEVICE 956 bool "Device controller for cgroups" 957 help 958 Provides a cgroup implementing whitelists for devices which 959 a process in the cgroup can mknod or open. 960 961config CPUSETS 962 bool "Cpuset support" 963 help 964 This option will let you create and manage CPUSETs which 965 allow dynamically partitioning a system into sets of CPUs and 966 Memory Nodes and assigning tasks to run only within those sets. 967 This is primarily useful on large SMP or NUMA systems. 968 969 Say N if unsure. 970 971config PROC_PID_CPUSET 972 bool "Include legacy /proc/<pid>/cpuset file" 973 depends on CPUSETS 974 default y 975 976config CGROUP_CPUACCT 977 bool "Simple CPU accounting cgroup subsystem" 978 help 979 Provides a simple Resource Controller for monitoring the 980 total CPU consumed by the tasks in a cgroup. 981 982config RESOURCE_COUNTERS 983 bool "Resource counters" 984 help 985 This option enables controller independent resource accounting 986 infrastructure that works with cgroups. 987 988config MEMCG 989 bool "Memory Resource Controller for Control Groups" 990 depends on RESOURCE_COUNTERS 991 select EVENTFD 992 help 993 Provides a memory resource controller that manages both anonymous 994 memory and page cache. (See Documentation/cgroups/memory.txt) 995 996 Note that setting this option increases fixed memory overhead 997 associated with each page of memory in the system. By this, 998 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 999 usage tracking struct at boot. Total amount of this is printed out 1000 at boot. 1001 1002 Only enable when you're ok with these trade offs and really 1003 sure you need the memory resource controller. Even when you enable 1004 this, you can set "cgroup_disable=memory" at your boot option to 1005 disable memory resource controller and you can avoid overheads. 1006 (and lose benefits of memory resource controller) 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 1050 WARNING: Current implementation lacks reclaim support. That means 1051 allocation attempts will fail when close to the limit even if there 1052 are plenty of kmem available for reclaim. That makes this option 1053 unusable in real life so DO NOT SELECT IT unless for development 1054 purposes. 1055 1056config CGROUP_HUGETLB 1057 bool "HugeTLB Resource Controller for Control Groups" 1058 depends on RESOURCE_COUNTERS && HUGETLB_PAGE 1059 default n 1060 help 1061 Provides a cgroup Resource Controller for HugeTLB pages. 1062 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1063 The limit is enforced during page fault. Since HugeTLB doesn't 1064 support page reclaim, enforcing the limit at page fault time implies 1065 that, the application will get SIGBUS signal if it tries to access 1066 HugeTLB pages beyond its limit. This requires the application to know 1067 beforehand how much HugeTLB pages it would require for its use. The 1068 control group is tracked in the third page lru pointer. This means 1069 that we cannot use the controller with huge page less than 3 pages. 1070 1071config CGROUP_PERF 1072 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 1073 depends on PERF_EVENTS && CGROUPS 1074 help 1075 This option extends the per-cpu mode to restrict monitoring to 1076 threads which belong to the cgroup specified and run on the 1077 designated cpu. 1078 1079 Say N if unsure. 1080 1081menuconfig CGROUP_SCHED 1082 bool "Group CPU scheduler" 1083 default n 1084 help 1085 This feature lets CPU scheduler recognize task groups and control CPU 1086 bandwidth allocation to such task groups. It uses cgroups to group 1087 tasks. 1088 1089if CGROUP_SCHED 1090config FAIR_GROUP_SCHED 1091 bool "Group scheduling for SCHED_OTHER" 1092 depends on CGROUP_SCHED 1093 default CGROUP_SCHED 1094 1095config CFS_BANDWIDTH 1096 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1097 depends on FAIR_GROUP_SCHED 1098 default n 1099 help 1100 This option allows users to define CPU bandwidth rates (limits) for 1101 tasks running within the fair group scheduler. Groups with no limit 1102 set are considered to be unconstrained and will run with no 1103 restriction. 1104 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1105 1106config RT_GROUP_SCHED 1107 bool "Group scheduling for SCHED_RR/FIFO" 1108 depends on CGROUP_SCHED 1109 default n 1110 help 1111 This feature lets you explicitly allocate real CPU bandwidth 1112 to task groups. If enabled, it will also make it impossible to 1113 schedule realtime tasks for non-root users until you allocate 1114 realtime bandwidth for them. 1115 See Documentation/scheduler/sched-rt-group.txt for more information. 1116 1117endif #CGROUP_SCHED 1118 1119config BLK_CGROUP 1120 bool "Block IO controller" 1121 depends on BLOCK 1122 default n 1123 ---help--- 1124 Generic block IO controller cgroup interface. This is the common 1125 cgroup interface which should be used by various IO controlling 1126 policies. 1127 1128 Currently, CFQ IO scheduler uses it to recognize task groups and 1129 control disk bandwidth allocation (proportional time slice allocation) 1130 to such task groups. It is also used by bio throttling logic in 1131 block layer to implement upper limit in IO rates on a device. 1132 1133 This option only enables generic Block IO controller infrastructure. 1134 One needs to also enable actual IO controlling logic/policy. For 1135 enabling proportional weight division of disk bandwidth in CFQ, set 1136 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1137 CONFIG_BLK_DEV_THROTTLING=y. 1138 1139 See Documentation/cgroups/blkio-controller.txt for more information. 1140 1141config DEBUG_BLK_CGROUP 1142 bool "Enable Block IO controller debugging" 1143 depends on BLK_CGROUP 1144 default n 1145 ---help--- 1146 Enable some debugging help. Currently it exports additional stat 1147 files in a cgroup which can be useful for debugging. 1148 1149endif # CGROUPS 1150 1151config CHECKPOINT_RESTORE 1152 bool "Checkpoint/restore support" if EXPERT 1153 default n 1154 help 1155 Enables additional kernel features in a sake of checkpoint/restore. 1156 In particular it adds auxiliary prctl codes to setup process text, 1157 data and heap segment sizes, and a few additional /proc filesystem 1158 entries. 1159 1160 If unsure, say N here. 1161 1162menuconfig NAMESPACES 1163 bool "Namespaces support" if EXPERT 1164 default !EXPERT 1165 help 1166 Provides the way to make tasks work with different objects using 1167 the same id. For example same IPC id may refer to different objects 1168 or same user id or pid may refer to different tasks when used in 1169 different namespaces. 1170 1171if NAMESPACES 1172 1173config UTS_NS 1174 bool "UTS namespace" 1175 default y 1176 help 1177 In this namespace tasks see different info provided with the 1178 uname() system call 1179 1180config IPC_NS 1181 bool "IPC namespace" 1182 depends on (SYSVIPC || POSIX_MQUEUE) 1183 default y 1184 help 1185 In this namespace tasks work with IPC ids which correspond to 1186 different IPC objects in different namespaces. 1187 1188config USER_NS 1189 bool "User namespace" 1190 default n 1191 help 1192 This allows containers, i.e. vservers, to use user namespaces 1193 to provide different user info for different servers. 1194 1195 When user namespaces are enabled in the kernel it is 1196 recommended that the MEMCG and MEMCG_KMEM options also be 1197 enabled and that user-space use the memory control groups to 1198 limit the amount of memory a memory unprivileged users can 1199 use. 1200 1201 If unsure, say N. 1202 1203config PID_NS 1204 bool "PID Namespaces" 1205 default y 1206 help 1207 Support process id namespaces. This allows having multiple 1208 processes with the same pid as long as they are in different 1209 pid namespaces. This is a building block of containers. 1210 1211config NET_NS 1212 bool "Network namespace" 1213 depends on NET 1214 default y 1215 help 1216 Allow user space to create what appear to be multiple instances 1217 of the network stack. 1218 1219endif # NAMESPACES 1220 1221config SCHED_AUTOGROUP 1222 bool "Automatic process group scheduling" 1223 select CGROUPS 1224 select CGROUP_SCHED 1225 select FAIR_GROUP_SCHED 1226 help 1227 This option optimizes the scheduler for common desktop workloads by 1228 automatically creating and populating task groups. This separation 1229 of workloads isolates aggressive CPU burners (like build jobs) from 1230 desktop applications. Task group autogeneration is currently based 1231 upon task session. 1232 1233config SYSFS_DEPRECATED 1234 bool "Enable deprecated sysfs features to support old userspace tools" 1235 depends on SYSFS 1236 default n 1237 help 1238 This option adds code that switches the layout of the "block" class 1239 devices, to not show up in /sys/class/block/, but only in 1240 /sys/block/. 1241 1242 This switch is only active when the sysfs.deprecated=1 boot option is 1243 passed or the SYSFS_DEPRECATED_V2 option is set. 1244 1245 This option allows new kernels to run on old distributions and tools, 1246 which might get confused by /sys/class/block/. Since 2007/2008 all 1247 major distributions and tools handle this just fine. 1248 1249 Recent distributions and userspace tools after 2009/2010 depend on 1250 the existence of /sys/class/block/, and will not work with this 1251 option enabled. 1252 1253 Only if you are using a new kernel on an old distribution, you might 1254 need to say Y here. 1255 1256config SYSFS_DEPRECATED_V2 1257 bool "Enable deprecated sysfs features by default" 1258 default n 1259 depends on SYSFS 1260 depends on SYSFS_DEPRECATED 1261 help 1262 Enable deprecated sysfs by default. 1263 1264 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1265 option. 1266 1267 Only if you are using a new kernel on an old distribution, you might 1268 need to say Y here. Even then, odds are you would not need it 1269 enabled, you can always pass the boot option if absolutely necessary. 1270 1271config RELAY 1272 bool "Kernel->user space relay support (formerly relayfs)" 1273 help 1274 This option enables support for relay interface support in 1275 certain file systems (such as debugfs). 1276 It is designed to provide an efficient mechanism for tools and 1277 facilities to relay large amounts of data from kernel space to 1278 user space. 1279 1280 If unsure, say N. 1281 1282config BLK_DEV_INITRD 1283 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1284 depends on BROKEN || !FRV 1285 help 1286 The initial RAM filesystem is a ramfs which is loaded by the 1287 boot loader (loadlin or lilo) and that is mounted as root 1288 before the normal boot procedure. It is typically used to 1289 load modules needed to mount the "real" root file system, 1290 etc. See <file:Documentation/initrd.txt> for details. 1291 1292 If RAM disk support (BLK_DEV_RAM) is also included, this 1293 also enables initial RAM disk (initrd) support and adds 1294 15 Kbytes (more on some other architectures) to the kernel size. 1295 1296 If unsure say Y. 1297 1298if BLK_DEV_INITRD 1299 1300source "usr/Kconfig" 1301 1302endif 1303 1304config CC_OPTIMIZE_FOR_SIZE 1305 bool "Optimize for size" 1306 help 1307 Enabling this option will pass "-Os" instead of "-O2" to gcc 1308 resulting in a smaller kernel. 1309 1310 If unsure, say N. 1311 1312config SYSCTL 1313 bool 1314 1315config ANON_INODES 1316 bool 1317 1318config HAVE_UID16 1319 bool 1320 1321config SYSCTL_EXCEPTION_TRACE 1322 bool 1323 help 1324 Enable support for /proc/sys/debug/exception-trace. 1325 1326config SYSCTL_ARCH_UNALIGN_NO_WARN 1327 bool 1328 help 1329 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1330 Allows arch to define/use @no_unaligned_warning to possibly warn 1331 about unaligned access emulation going on under the hood. 1332 1333config SYSCTL_ARCH_UNALIGN_ALLOW 1334 bool 1335 help 1336 Enable support for /proc/sys/kernel/unaligned-trap 1337 Allows arches to define/use @unaligned_enabled to runtime toggle 1338 the unaligned access emulation. 1339 see arch/parisc/kernel/unaligned.c for reference 1340 1341config HAVE_PCSPKR_PLATFORM 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 1357 default y 1358 help 1359 This enables the legacy 16-bit UID syscall wrappers. 1360 1361config SGETMASK_SYSCALL 1362 bool "sgetmask/ssetmask syscalls support" if EXPERT 1363 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1364 ---help--- 1365 sys_sgetmask and sys_ssetmask are obsolete system calls 1366 no longer supported in libc but still enabled by default in some 1367 architectures. 1368 1369 If unsure, leave the default option here. 1370 1371config SYSFS_SYSCALL 1372 bool "Sysfs syscall support" if EXPERT 1373 default y 1374 ---help--- 1375 sys_sysfs is an obsolete system call no longer supported in libc. 1376 Note that disabling this option is more secure but might break 1377 compatibility with some systems. 1378 1379 If unsure say Y here. 1380 1381config SYSCTL_SYSCALL 1382 bool "Sysctl syscall support" if EXPERT 1383 depends on PROC_SYSCTL 1384 default n 1385 select SYSCTL 1386 ---help--- 1387 sys_sysctl uses binary paths that have been found challenging 1388 to properly maintain and use. The interface in /proc/sys 1389 using paths with ascii names is now the primary path to this 1390 information. 1391 1392 Almost nothing using the binary sysctl interface so if you are 1393 trying to save some space it is probably safe to disable this, 1394 making your kernel marginally smaller. 1395 1396 If unsure say N here. 1397 1398config KALLSYMS 1399 bool "Load all symbols for debugging/ksymoops" if EXPERT 1400 default y 1401 help 1402 Say Y here to let the kernel print out symbolic crash information and 1403 symbolic stack backtraces. This increases the size of the kernel 1404 somewhat, as all symbols have to be loaded into the kernel image. 1405 1406config KALLSYMS_ALL 1407 bool "Include all symbols in kallsyms" 1408 depends on DEBUG_KERNEL && KALLSYMS 1409 help 1410 Normally kallsyms only contains the symbols of functions for nicer 1411 OOPS messages and backtraces (i.e., symbols from the text and inittext 1412 sections). This is sufficient for most cases. And only in very rare 1413 cases (e.g., when a debugger is used) all symbols are required (e.g., 1414 names of variables from the data sections, etc). 1415 1416 This option makes sure that all symbols are loaded into the kernel 1417 image (i.e., symbols from all sections) in cost of increased kernel 1418 size (depending on the kernel configuration, it may be 300KiB or 1419 something like this). 1420 1421 Say N unless you really need all symbols. 1422 1423config PRINTK 1424 default y 1425 bool "Enable support for printk" if EXPERT 1426 select IRQ_WORK 1427 help 1428 This option enables normal printk support. Removing it 1429 eliminates most of the message strings from the kernel image 1430 and makes the kernel more or less silent. As this makes it 1431 very difficult to diagnose system problems, saying N here is 1432 strongly discouraged. 1433 1434config BUG 1435 bool "BUG() support" if EXPERT 1436 default y 1437 help 1438 Disabling this option eliminates support for BUG and WARN, reducing 1439 the size of your kernel image and potentially quietly ignoring 1440 numerous fatal conditions. You should only consider disabling this 1441 option for embedded systems with no facilities for reporting errors. 1442 Just say Y. 1443 1444config ELF_CORE 1445 depends on COREDUMP 1446 default y 1447 bool "Enable ELF core dumps" if EXPERT 1448 help 1449 Enable support for generating core dumps. Disabling saves about 4k. 1450 1451 1452config PCSPKR_PLATFORM 1453 bool "Enable PC-Speaker support" if EXPERT 1454 depends on HAVE_PCSPKR_PLATFORM 1455 select I8253_LOCK 1456 default y 1457 help 1458 This option allows to disable the internal PC-Speaker 1459 support, saving some memory. 1460 1461config BASE_FULL 1462 default y 1463 bool "Enable full-sized data structures for core" if EXPERT 1464 help 1465 Disabling this option reduces the size of miscellaneous core 1466 kernel data structures. This saves memory on small machines, 1467 but may reduce performance. 1468 1469config FUTEX 1470 bool "Enable futex support" if EXPERT 1471 default y 1472 select RT_MUTEXES 1473 help 1474 Disabling this option will cause the kernel to be built without 1475 support for "fast userspace mutexes". The resulting kernel may not 1476 run glibc-based applications correctly. 1477 1478config HAVE_FUTEX_CMPXCHG 1479 bool 1480 depends on FUTEX 1481 help 1482 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1483 is implemented and always working. This removes a couple of runtime 1484 checks. 1485 1486config EPOLL 1487 bool "Enable eventpoll support" if EXPERT 1488 default y 1489 select ANON_INODES 1490 help 1491 Disabling this option will cause the kernel to be built without 1492 support for epoll family of system calls. 1493 1494config SIGNALFD 1495 bool "Enable signalfd() system call" if EXPERT 1496 select ANON_INODES 1497 default y 1498 help 1499 Enable the signalfd() system call that allows to receive signals 1500 on a file descriptor. 1501 1502 If unsure, say Y. 1503 1504config TIMERFD 1505 bool "Enable timerfd() system call" if EXPERT 1506 select ANON_INODES 1507 default y 1508 help 1509 Enable the timerfd() system call that allows to receive timer 1510 events on a file descriptor. 1511 1512 If unsure, say Y. 1513 1514config EVENTFD 1515 bool "Enable eventfd() system call" if EXPERT 1516 select ANON_INODES 1517 default y 1518 help 1519 Enable the eventfd() system call that allows to receive both 1520 kernel notification (ie. KAIO) or userspace notifications. 1521 1522 If unsure, say Y. 1523 1524config SHMEM 1525 bool "Use full shmem filesystem" if EXPERT 1526 default y 1527 depends on MMU 1528 help 1529 The shmem is an internal filesystem used to manage shared memory. 1530 It is backed by swap and manages resource limits. It is also exported 1531 to userspace as tmpfs if TMPFS is enabled. Disabling this 1532 option replaces shmem and tmpfs with the much simpler ramfs code, 1533 which may be appropriate on small systems without swap. 1534 1535config AIO 1536 bool "Enable AIO support" if EXPERT 1537 default y 1538 help 1539 This option enables POSIX asynchronous I/O which may by used 1540 by some high performance threaded applications. Disabling 1541 this option saves about 7k. 1542 1543config PCI_QUIRKS 1544 default y 1545 bool "Enable PCI quirk workarounds" if EXPERT 1546 depends on PCI 1547 help 1548 This enables workarounds for various PCI chipset 1549 bugs/quirks. Disable this only if your target machine is 1550 unaffected by PCI quirks. 1551 1552config EMBEDDED 1553 bool "Embedded system" 1554 option allnoconfig_y 1555 select EXPERT 1556 help 1557 This option should be enabled if compiling the kernel for 1558 an embedded system so certain expert options are available 1559 for configuration. 1560 1561config HAVE_PERF_EVENTS 1562 bool 1563 help 1564 See tools/perf/design.txt for details. 1565 1566config PERF_USE_VMALLOC 1567 bool 1568 help 1569 See tools/perf/design.txt for details 1570 1571menu "Kernel Performance Events And Counters" 1572 1573config PERF_EVENTS 1574 bool "Kernel performance events and counters" 1575 default y if PROFILING 1576 depends on HAVE_PERF_EVENTS 1577 select ANON_INODES 1578 select IRQ_WORK 1579 help 1580 Enable kernel support for various performance events provided 1581 by software and hardware. 1582 1583 Software events are supported either built-in or via the 1584 use of generic tracepoints. 1585 1586 Most modern CPUs support performance events via performance 1587 counter registers. These registers count the number of certain 1588 types of hw events: such as instructions executed, cachemisses 1589 suffered, or branches mis-predicted - without slowing down the 1590 kernel or applications. These registers can also trigger interrupts 1591 when a threshold number of events have passed - and can thus be 1592 used to profile the code that runs on that CPU. 1593 1594 The Linux Performance Event subsystem provides an abstraction of 1595 these software and hardware event capabilities, available via a 1596 system call and used by the "perf" utility in tools/perf/. It 1597 provides per task and per CPU counters, and it provides event 1598 capabilities on top of those. 1599 1600 Say Y if unsure. 1601 1602config DEBUG_PERF_USE_VMALLOC 1603 default n 1604 bool "Debug: use vmalloc to back perf mmap() buffers" 1605 depends on PERF_EVENTS && DEBUG_KERNEL 1606 select PERF_USE_VMALLOC 1607 help 1608 Use vmalloc memory to back perf mmap() buffers. 1609 1610 Mostly useful for debugging the vmalloc code on platforms 1611 that don't require it. 1612 1613 Say N if unsure. 1614 1615endmenu 1616 1617config VM_EVENT_COUNTERS 1618 default y 1619 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1620 help 1621 VM event counters are needed for event counts to be shown. 1622 This option allows the disabling of the VM event counters 1623 on EXPERT systems. /proc/vmstat will only show page counts 1624 if VM event counters are disabled. 1625 1626config SLUB_DEBUG 1627 default y 1628 bool "Enable SLUB debugging support" if EXPERT 1629 depends on SLUB && SYSFS 1630 help 1631 SLUB has extensive debug support features. Disabling these can 1632 result in significant savings in code size. This also disables 1633 SLUB sysfs support. /sys/slab will not exist and there will be 1634 no support for cache validation etc. 1635 1636config COMPAT_BRK 1637 bool "Disable heap randomization" 1638 default y 1639 help 1640 Randomizing heap placement makes heap exploits harder, but it 1641 also breaks ancient binaries (including anything libc5 based). 1642 This option changes the bootup default to heap randomization 1643 disabled, and can be overridden at runtime by setting 1644 /proc/sys/kernel/randomize_va_space to 2. 1645 1646 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1647 1648choice 1649 prompt "Choose SLAB allocator" 1650 default SLUB 1651 help 1652 This option allows to select a slab allocator. 1653 1654config SLAB 1655 bool "SLAB" 1656 help 1657 The regular slab allocator that is established and known to work 1658 well in all environments. It organizes cache hot objects in 1659 per cpu and per node queues. 1660 1661config SLUB 1662 bool "SLUB (Unqueued Allocator)" 1663 help 1664 SLUB is a slab allocator that minimizes cache line usage 1665 instead of managing queues of cached objects (SLAB approach). 1666 Per cpu caching is realized using slabs of objects instead 1667 of queues of objects. SLUB can use memory efficiently 1668 and has enhanced diagnostics. SLUB is the default choice for 1669 a slab allocator. 1670 1671config SLOB 1672 depends on EXPERT 1673 bool "SLOB (Simple Allocator)" 1674 help 1675 SLOB replaces the stock allocator with a drastically simpler 1676 allocator. SLOB is generally more space efficient but 1677 does not perform as well on large systems. 1678 1679endchoice 1680 1681config SLUB_CPU_PARTIAL 1682 default y 1683 depends on SLUB && SMP 1684 bool "SLUB per cpu partial cache" 1685 help 1686 Per cpu partial caches accellerate objects allocation and freeing 1687 that is local to a processor at the price of more indeterminism 1688 in the latency of the free. On overflow these caches will be cleared 1689 which requires the taking of locks that may cause latency spikes. 1690 Typically one would choose no for a realtime system. 1691 1692config MMAP_ALLOW_UNINITIALIZED 1693 bool "Allow mmapped anonymous memory to be uninitialized" 1694 depends on EXPERT && !MMU 1695 default n 1696 help 1697 Normally, and according to the Linux spec, anonymous memory obtained 1698 from mmap() has it's contents cleared before it is passed to 1699 userspace. Enabling this config option allows you to request that 1700 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1701 providing a huge performance boost. If this option is not enabled, 1702 then the flag will be ignored. 1703 1704 This is taken advantage of by uClibc's malloc(), and also by 1705 ELF-FDPIC binfmt's brk and stack allocator. 1706 1707 Because of the obvious security issues, this option should only be 1708 enabled on embedded devices where you control what is run in 1709 userspace. Since that isn't generally a problem on no-MMU systems, 1710 it is normally safe to say Y here. 1711 1712 See Documentation/nommu-mmap.txt for more information. 1713 1714config SYSTEM_TRUSTED_KEYRING 1715 bool "Provide system-wide ring of trusted keys" 1716 depends on KEYS 1717 help 1718 Provide a system keyring to which trusted keys can be added. Keys in 1719 the keyring are considered to be trusted. Keys may be added at will 1720 by the kernel from compiled-in data and from hardware key stores, but 1721 userspace may only add extra keys if those keys can be verified by 1722 keys already in the keyring. 1723 1724 Keys in this keyring are used by module signature checking. 1725 1726config PROFILING 1727 bool "Profiling support" 1728 help 1729 Say Y here to enable the extended profiling support mechanisms used 1730 by profilers such as OProfile. 1731 1732# 1733# Place an empty function call at each tracepoint site. Can be 1734# dynamically changed for a probe function. 1735# 1736config TRACEPOINTS 1737 bool 1738 1739source "arch/Kconfig" 1740 1741endmenu # General setup 1742 1743config HAVE_GENERIC_DMA_COHERENT 1744 bool 1745 default n 1746 1747config SLABINFO 1748 bool 1749 depends on PROC_FS 1750 depends on SLAB || SLUB_DEBUG 1751 default y 1752 1753config RT_MUTEXES 1754 boolean 1755 1756config BASE_SMALL 1757 int 1758 default 0 if BASE_FULL 1759 default 1 if !BASE_FULL 1760 1761menuconfig MODULES 1762 bool "Enable loadable module support" 1763 option modules 1764 help 1765 Kernel modules are small pieces of compiled code which can 1766 be inserted in the running kernel, rather than being 1767 permanently built into the kernel. You use the "modprobe" 1768 tool to add (and sometimes remove) them. If you say Y here, 1769 many parts of the kernel can be built as modules (by 1770 answering M instead of Y where indicated): this is most 1771 useful for infrequently used options which are not required 1772 for booting. For more information, see the man pages for 1773 modprobe, lsmod, modinfo, insmod and rmmod. 1774 1775 If you say Y here, you will need to run "make 1776 modules_install" to put the modules under /lib/modules/ 1777 where modprobe can find them (you may need to be root to do 1778 this). 1779 1780 If unsure, say Y. 1781 1782if MODULES 1783 1784config MODULE_FORCE_LOAD 1785 bool "Forced module loading" 1786 default n 1787 help 1788 Allow loading of modules without version information (ie. modprobe 1789 --force). Forced module loading sets the 'F' (forced) taint flag and 1790 is usually a really bad idea. 1791 1792config MODULE_UNLOAD 1793 bool "Module unloading" 1794 help 1795 Without this option you will not be able to unload any 1796 modules (note that some modules may not be unloadable 1797 anyway), which makes your kernel smaller, faster 1798 and simpler. If unsure, say Y. 1799 1800config MODULE_FORCE_UNLOAD 1801 bool "Forced module unloading" 1802 depends on MODULE_UNLOAD 1803 help 1804 This option allows you to force a module to unload, even if the 1805 kernel believes it is unsafe: the kernel will remove the module 1806 without waiting for anyone to stop using it (using the -f option to 1807 rmmod). This is mainly for kernel developers and desperate users. 1808 If unsure, say N. 1809 1810config MODVERSIONS 1811 bool "Module versioning support" 1812 help 1813 Usually, you have to use modules compiled with your kernel. 1814 Saying Y here makes it sometimes possible to use modules 1815 compiled for different kernels, by adding enough information 1816 to the modules to (hopefully) spot any changes which would 1817 make them incompatible with the kernel you are running. If 1818 unsure, say N. 1819 1820config MODULE_SRCVERSION_ALL 1821 bool "Source checksum for all modules" 1822 help 1823 Modules which contain a MODULE_VERSION get an extra "srcversion" 1824 field inserted into their modinfo section, which contains a 1825 sum of the source files which made it. This helps maintainers 1826 see exactly which source was used to build a module (since 1827 others sometimes change the module source without updating 1828 the version). With this option, such a "srcversion" field 1829 will be created for all modules. If unsure, say N. 1830 1831config MODULE_SIG 1832 bool "Module signature verification" 1833 depends on MODULES 1834 select SYSTEM_TRUSTED_KEYRING 1835 select KEYS 1836 select CRYPTO 1837 select ASYMMETRIC_KEY_TYPE 1838 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1839 select PUBLIC_KEY_ALGO_RSA 1840 select ASN1 1841 select OID_REGISTRY 1842 select X509_CERTIFICATE_PARSER 1843 help 1844 Check modules for valid signatures upon load: the signature 1845 is simply appended to the module. For more information see 1846 Documentation/module-signing.txt. 1847 1848 !!!WARNING!!! If you enable this option, you MUST make sure that the 1849 module DOES NOT get stripped after being signed. This includes the 1850 debuginfo strip done by some packagers (such as rpmbuild) and 1851 inclusion into an initramfs that wants the module size reduced. 1852 1853config MODULE_SIG_FORCE 1854 bool "Require modules to be validly signed" 1855 depends on MODULE_SIG 1856 help 1857 Reject unsigned modules or signed modules for which we don't have a 1858 key. Without this, such modules will simply taint the kernel. 1859 1860config MODULE_SIG_ALL 1861 bool "Automatically sign all modules" 1862 default y 1863 depends on MODULE_SIG 1864 help 1865 Sign all modules during make modules_install. Without this option, 1866 modules must be signed manually, using the scripts/sign-file tool. 1867 1868comment "Do not forget to sign required modules with scripts/sign-file" 1869 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1870 1871choice 1872 prompt "Which hash algorithm should modules be signed with?" 1873 depends on MODULE_SIG 1874 help 1875 This determines which sort of hashing algorithm will be used during 1876 signature generation. This algorithm _must_ be built into the kernel 1877 directly so that signature verification can take place. It is not 1878 possible to load a signed module containing the algorithm to check 1879 the signature on that module. 1880 1881config MODULE_SIG_SHA1 1882 bool "Sign modules with SHA-1" 1883 select CRYPTO_SHA1 1884 1885config MODULE_SIG_SHA224 1886 bool "Sign modules with SHA-224" 1887 select CRYPTO_SHA256 1888 1889config MODULE_SIG_SHA256 1890 bool "Sign modules with SHA-256" 1891 select CRYPTO_SHA256 1892 1893config MODULE_SIG_SHA384 1894 bool "Sign modules with SHA-384" 1895 select CRYPTO_SHA512 1896 1897config MODULE_SIG_SHA512 1898 bool "Sign modules with SHA-512" 1899 select CRYPTO_SHA512 1900 1901endchoice 1902 1903config MODULE_SIG_HASH 1904 string 1905 depends on MODULE_SIG 1906 default "sha1" if MODULE_SIG_SHA1 1907 default "sha224" if MODULE_SIG_SHA224 1908 default "sha256" if MODULE_SIG_SHA256 1909 default "sha384" if MODULE_SIG_SHA384 1910 default "sha512" if MODULE_SIG_SHA512 1911 1912endif # MODULES 1913 1914config INIT_ALL_POSSIBLE 1915 bool 1916 help 1917 Back when each arch used to define their own cpu_online_mask and 1918 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1919 with all 1s, and others with all 0s. When they were centralised, 1920 it was better to provide this option than to break all the archs 1921 and have several arch maintainers pursuing me down dark alleys. 1922 1923config STOP_MACHINE 1924 bool 1925 default y 1926 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1927 help 1928 Need stop_machine() primitive. 1929 1930source "block/Kconfig" 1931 1932config PREEMPT_NOTIFIERS 1933 bool 1934 1935config PADATA 1936 depends on SMP 1937 bool 1938 1939# Can be selected by architectures with broken toolchains 1940# that get confused by correct const<->read_only section 1941# mappings 1942config BROKEN_RODATA 1943 bool 1944 1945config ASN1 1946 tristate 1947 help 1948 Build a simple ASN.1 grammar compiler that produces a bytecode output 1949 that can be interpreted by the ASN.1 stream decoder and used to 1950 inform it as to what tags are to be expected in a stream and what 1951 functions to call on what tags. 1952 1953source "kernel/Kconfig.locks" 1954