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 to another process's 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 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 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 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 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 IKCONFIG 787 tristate "Kernel .config support" 788 ---help--- 789 This option enables the complete Linux kernel ".config" file 790 contents to be saved in the kernel. It provides documentation 791 of which kernel options are used in a running kernel or in an 792 on-disk kernel. This information can be extracted from the kernel 793 image file with the script scripts/extract-ikconfig and used as 794 input to rebuild the current kernel or to build another kernel. 795 It can also be extracted from a running kernel by reading 796 /proc/config.gz if enabled (below). 797 798config IKCONFIG_PROC 799 bool "Enable access to .config through /proc/config.gz" 800 depends on IKCONFIG && PROC_FS 801 ---help--- 802 This option enables access to the kernel configuration file 803 through /proc/config.gz. 804 805config LOG_BUF_SHIFT 806 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 807 range 12 21 808 default 17 809 help 810 Select kernel log buffer size as a power of 2. 811 Examples: 812 17 => 128 KB 813 16 => 64 KB 814 15 => 32 KB 815 14 => 16 KB 816 13 => 8 KB 817 12 => 4 KB 818 819# 820# Architectures with an unreliable sched_clock() should select this: 821# 822config HAVE_UNSTABLE_SCHED_CLOCK 823 bool 824 825config GENERIC_SCHED_CLOCK 826 bool 827 828# 829# For architectures that want to enable the support for NUMA-affine scheduler 830# balancing logic: 831# 832config ARCH_SUPPORTS_NUMA_BALANCING 833 bool 834 835# 836# For architectures that know their GCC __int128 support is sound 837# 838config ARCH_SUPPORTS_INT128 839 bool 840 841# For architectures that (ab)use NUMA to represent different memory regions 842# all cpu-local but of different latencies, such as SuperH. 843# 844config ARCH_WANT_NUMA_VARIABLE_LOCALITY 845 bool 846 847# 848# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE 849config ARCH_WANTS_PROT_NUMA_PROT_NONE 850 bool 851 852config ARCH_USES_NUMA_PROT_NONE 853 bool 854 default y 855 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE 856 depends on NUMA_BALANCING 857 858config NUMA_BALANCING_DEFAULT_ENABLED 859 bool "Automatically enable NUMA aware memory/task placement" 860 default y 861 depends on NUMA_BALANCING 862 help 863 If set, automatic NUMA balancing will be enabled if running on a NUMA 864 machine. 865 866config NUMA_BALANCING 867 bool "Memory placement aware NUMA scheduler" 868 depends on ARCH_SUPPORTS_NUMA_BALANCING 869 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 870 depends on SMP && NUMA && MIGRATION 871 help 872 This option adds support for automatic NUMA aware memory/task placement. 873 The mechanism is quite primitive and is based on migrating memory when 874 it has references to the node the task is running on. 875 876 This system will be inactive on UMA systems. 877 878menuconfig CGROUPS 879 boolean "Control Group support" 880 select KERNFS 881 help 882 This option adds support for grouping sets of processes together, for 883 use with process control subsystems such as Cpusets, CFS, memory 884 controls or device isolation. 885 See 886 - Documentation/scheduler/sched-design-CFS.txt (CFS) 887 - Documentation/cgroups/ (features for grouping, isolation 888 and resource control) 889 890 Say N if unsure. 891 892if CGROUPS 893 894config CGROUP_DEBUG 895 bool "Example debug cgroup subsystem" 896 default n 897 help 898 This option enables a simple cgroup subsystem that 899 exports useful debugging information about the cgroups 900 framework. 901 902 Say N if unsure. 903 904config CGROUP_FREEZER 905 bool "Freezer cgroup subsystem" 906 help 907 Provides a way to freeze and unfreeze all tasks in a 908 cgroup. 909 910config CGROUP_DEVICE 911 bool "Device controller for cgroups" 912 help 913 Provides a cgroup implementing whitelists for devices which 914 a process in the cgroup can mknod or open. 915 916config CPUSETS 917 bool "Cpuset support" 918 help 919 This option will let you create and manage CPUSETs which 920 allow dynamically partitioning a system into sets of CPUs and 921 Memory Nodes and assigning tasks to run only within those sets. 922 This is primarily useful on large SMP or NUMA systems. 923 924 Say N if unsure. 925 926config PROC_PID_CPUSET 927 bool "Include legacy /proc/<pid>/cpuset file" 928 depends on CPUSETS 929 default y 930 931config CGROUP_CPUACCT 932 bool "Simple CPU accounting cgroup subsystem" 933 help 934 Provides a simple Resource Controller for monitoring the 935 total CPU consumed by the tasks in a cgroup. 936 937config RESOURCE_COUNTERS 938 bool "Resource counters" 939 help 940 This option enables controller independent resource accounting 941 infrastructure that works with cgroups. 942 943config MEMCG 944 bool "Memory Resource Controller for Control Groups" 945 depends on RESOURCE_COUNTERS 946 select EVENTFD 947 help 948 Provides a memory resource controller that manages both anonymous 949 memory and page cache. (See Documentation/cgroups/memory.txt) 950 951 Note that setting this option increases fixed memory overhead 952 associated with each page of memory in the system. By this, 953 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 954 usage tracking struct at boot. Total amount of this is printed out 955 at boot. 956 957 Only enable when you're ok with these trade offs and really 958 sure you need the memory resource controller. Even when you enable 959 this, you can set "cgroup_disable=memory" at your boot option to 960 disable memory resource controller and you can avoid overheads. 961 (and lose benefits of memory resource controller) 962 963config MEMCG_SWAP 964 bool "Memory Resource Controller Swap Extension" 965 depends on MEMCG && SWAP 966 help 967 Add swap management feature to memory resource controller. When you 968 enable this, you can limit mem+swap usage per cgroup. In other words, 969 when you disable this, memory resource controller has no cares to 970 usage of swap...a process can exhaust all of the swap. This extension 971 is useful when you want to avoid exhaustion swap but this itself 972 adds more overheads and consumes memory for remembering information. 973 Especially if you use 32bit system or small memory system, please 974 be careful about enabling this. When memory resource controller 975 is disabled by boot option, this will be automatically disabled and 976 there will be no overhead from this. Even when you set this config=y, 977 if boot option "swapaccount=0" is set, swap will not be accounted. 978 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 979 size is 4096bytes, 512k per 1Gbytes of swap. 980config MEMCG_SWAP_ENABLED 981 bool "Memory Resource Controller Swap Extension enabled by default" 982 depends on MEMCG_SWAP 983 default y 984 help 985 Memory Resource Controller Swap Extension comes with its price in 986 a bigger memory consumption. General purpose distribution kernels 987 which want to enable the feature but keep it disabled by default 988 and let the user enable it by swapaccount=1 boot command line 989 parameter should have this option unselected. 990 For those who want to have the feature enabled by default should 991 select this option (if, for some reason, they need to disable it 992 then swapaccount=0 does the trick). 993config MEMCG_KMEM 994 bool "Memory Resource Controller Kernel Memory accounting" 995 depends on MEMCG 996 depends on SLUB || SLAB 997 help 998 The Kernel Memory extension for Memory Resource Controller can limit 999 the amount of memory used by kernel objects in the system. Those are 1000 fundamentally different from the entities handled by the standard 1001 Memory Controller, which are page-based, and can be swapped. Users of 1002 the kmem extension can use it to guarantee that no group of processes 1003 will ever exhaust kernel resources alone. 1004 1005 WARNING: Current implementation lacks reclaim support. That means 1006 allocation attempts will fail when close to the limit even if there 1007 are plenty of kmem available for reclaim. That makes this option 1008 unusable in real life so DO NOT SELECT IT unless for development 1009 purposes. 1010 1011config CGROUP_HUGETLB 1012 bool "HugeTLB Resource Controller for Control Groups" 1013 depends on RESOURCE_COUNTERS && HUGETLB_PAGE 1014 default n 1015 help 1016 Provides a cgroup Resource Controller for HugeTLB pages. 1017 When you enable this, you can put a per cgroup limit on HugeTLB usage. 1018 The limit is enforced during page fault. Since HugeTLB doesn't 1019 support page reclaim, enforcing the limit at page fault time implies 1020 that, the application will get SIGBUS signal if it tries to access 1021 HugeTLB pages beyond its limit. This requires the application to know 1022 beforehand how much HugeTLB pages it would require for its use. The 1023 control group is tracked in the third page lru pointer. This means 1024 that we cannot use the controller with huge page less than 3 pages. 1025 1026config CGROUP_PERF 1027 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 1028 depends on PERF_EVENTS && CGROUPS 1029 help 1030 This option extends the per-cpu mode to restrict monitoring to 1031 threads which belong to the cgroup specified and run on the 1032 designated cpu. 1033 1034 Say N if unsure. 1035 1036menuconfig CGROUP_SCHED 1037 bool "Group CPU scheduler" 1038 default n 1039 help 1040 This feature lets CPU scheduler recognize task groups and control CPU 1041 bandwidth allocation to such task groups. It uses cgroups to group 1042 tasks. 1043 1044if CGROUP_SCHED 1045config FAIR_GROUP_SCHED 1046 bool "Group scheduling for SCHED_OTHER" 1047 depends on CGROUP_SCHED 1048 default CGROUP_SCHED 1049 1050config CFS_BANDWIDTH 1051 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 1052 depends on FAIR_GROUP_SCHED 1053 default n 1054 help 1055 This option allows users to define CPU bandwidth rates (limits) for 1056 tasks running within the fair group scheduler. Groups with no limit 1057 set are considered to be unconstrained and will run with no 1058 restriction. 1059 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1060 1061config RT_GROUP_SCHED 1062 bool "Group scheduling for SCHED_RR/FIFO" 1063 depends on CGROUP_SCHED 1064 default n 1065 help 1066 This feature lets you explicitly allocate real CPU bandwidth 1067 to task groups. If enabled, it will also make it impossible to 1068 schedule realtime tasks for non-root users until you allocate 1069 realtime bandwidth for them. 1070 See Documentation/scheduler/sched-rt-group.txt for more information. 1071 1072endif #CGROUP_SCHED 1073 1074config BLK_CGROUP 1075 bool "Block IO controller" 1076 depends on BLOCK 1077 default n 1078 ---help--- 1079 Generic block IO controller cgroup interface. This is the common 1080 cgroup interface which should be used by various IO controlling 1081 policies. 1082 1083 Currently, CFQ IO scheduler uses it to recognize task groups and 1084 control disk bandwidth allocation (proportional time slice allocation) 1085 to such task groups. It is also used by bio throttling logic in 1086 block layer to implement upper limit in IO rates on a device. 1087 1088 This option only enables generic Block IO controller infrastructure. 1089 One needs to also enable actual IO controlling logic/policy. For 1090 enabling proportional weight division of disk bandwidth in CFQ, set 1091 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1092 CONFIG_BLK_DEV_THROTTLING=y. 1093 1094 See Documentation/cgroups/blkio-controller.txt for more information. 1095 1096config DEBUG_BLK_CGROUP 1097 bool "Enable Block IO controller debugging" 1098 depends on BLK_CGROUP 1099 default n 1100 ---help--- 1101 Enable some debugging help. Currently it exports additional stat 1102 files in a cgroup which can be useful for debugging. 1103 1104endif # CGROUPS 1105 1106config CHECKPOINT_RESTORE 1107 bool "Checkpoint/restore support" if EXPERT 1108 default n 1109 help 1110 Enables additional kernel features in a sake of checkpoint/restore. 1111 In particular it adds auxiliary prctl codes to setup process text, 1112 data and heap segment sizes, and a few additional /proc filesystem 1113 entries. 1114 1115 If unsure, say N here. 1116 1117menuconfig NAMESPACES 1118 bool "Namespaces support" if EXPERT 1119 default !EXPERT 1120 help 1121 Provides the way to make tasks work with different objects using 1122 the same id. For example same IPC id may refer to different objects 1123 or same user id or pid may refer to different tasks when used in 1124 different namespaces. 1125 1126if NAMESPACES 1127 1128config UTS_NS 1129 bool "UTS namespace" 1130 default y 1131 help 1132 In this namespace tasks see different info provided with the 1133 uname() system call 1134 1135config IPC_NS 1136 bool "IPC namespace" 1137 depends on (SYSVIPC || POSIX_MQUEUE) 1138 default y 1139 help 1140 In this namespace tasks work with IPC ids which correspond to 1141 different IPC objects in different namespaces. 1142 1143config USER_NS 1144 bool "User namespace" 1145 default n 1146 help 1147 This allows containers, i.e. vservers, to use user namespaces 1148 to provide different user info for different servers. 1149 1150 When user namespaces are enabled in the kernel it is 1151 recommended that the MEMCG and MEMCG_KMEM options also be 1152 enabled and that user-space use the memory control groups to 1153 limit the amount of memory a memory unprivileged users can 1154 use. 1155 1156 If unsure, say N. 1157 1158config PID_NS 1159 bool "PID Namespaces" 1160 default y 1161 help 1162 Support process id namespaces. This allows having multiple 1163 processes with the same pid as long as they are in different 1164 pid namespaces. This is a building block of containers. 1165 1166config NET_NS 1167 bool "Network namespace" 1168 depends on NET 1169 default y 1170 help 1171 Allow user space to create what appear to be multiple instances 1172 of the network stack. 1173 1174endif # NAMESPACES 1175 1176config SCHED_AUTOGROUP 1177 bool "Automatic process group scheduling" 1178 select CGROUPS 1179 select CGROUP_SCHED 1180 select FAIR_GROUP_SCHED 1181 help 1182 This option optimizes the scheduler for common desktop workloads by 1183 automatically creating and populating task groups. This separation 1184 of workloads isolates aggressive CPU burners (like build jobs) from 1185 desktop applications. Task group autogeneration is currently based 1186 upon task session. 1187 1188config SYSFS_DEPRECATED 1189 bool "Enable deprecated sysfs features to support old userspace tools" 1190 depends on SYSFS 1191 default n 1192 help 1193 This option adds code that switches the layout of the "block" class 1194 devices, to not show up in /sys/class/block/, but only in 1195 /sys/block/. 1196 1197 This switch is only active when the sysfs.deprecated=1 boot option is 1198 passed or the SYSFS_DEPRECATED_V2 option is set. 1199 1200 This option allows new kernels to run on old distributions and tools, 1201 which might get confused by /sys/class/block/. Since 2007/2008 all 1202 major distributions and tools handle this just fine. 1203 1204 Recent distributions and userspace tools after 2009/2010 depend on 1205 the existence of /sys/class/block/, and will not work with this 1206 option enabled. 1207 1208 Only if you are using a new kernel on an old distribution, you might 1209 need to say Y here. 1210 1211config SYSFS_DEPRECATED_V2 1212 bool "Enable deprecated sysfs features by default" 1213 default n 1214 depends on SYSFS 1215 depends on SYSFS_DEPRECATED 1216 help 1217 Enable deprecated sysfs by default. 1218 1219 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1220 option. 1221 1222 Only if you are using a new kernel on an old distribution, you might 1223 need to say Y here. Even then, odds are you would not need it 1224 enabled, you can always pass the boot option if absolutely necessary. 1225 1226config RELAY 1227 bool "Kernel->user space relay support (formerly relayfs)" 1228 help 1229 This option enables support for relay interface support in 1230 certain file systems (such as debugfs). 1231 It is designed to provide an efficient mechanism for tools and 1232 facilities to relay large amounts of data from kernel space to 1233 user space. 1234 1235 If unsure, say N. 1236 1237config BLK_DEV_INITRD 1238 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1239 depends on BROKEN || !FRV 1240 help 1241 The initial RAM filesystem is a ramfs which is loaded by the 1242 boot loader (loadlin or lilo) and that is mounted as root 1243 before the normal boot procedure. It is typically used to 1244 load modules needed to mount the "real" root file system, 1245 etc. See <file:Documentation/initrd.txt> for details. 1246 1247 If RAM disk support (BLK_DEV_RAM) is also included, this 1248 also enables initial RAM disk (initrd) support and adds 1249 15 Kbytes (more on some other architectures) to the kernel size. 1250 1251 If unsure say Y. 1252 1253if BLK_DEV_INITRD 1254 1255source "usr/Kconfig" 1256 1257endif 1258 1259config CC_OPTIMIZE_FOR_SIZE 1260 bool "Optimize for size" 1261 help 1262 Enabling this option will pass "-Os" instead of "-O2" to gcc 1263 resulting in a smaller kernel. 1264 1265 If unsure, say N. 1266 1267config SYSCTL 1268 bool 1269 1270config ANON_INODES 1271 bool 1272 1273config HAVE_UID16 1274 bool 1275 1276config SYSCTL_EXCEPTION_TRACE 1277 bool 1278 help 1279 Enable support for /proc/sys/debug/exception-trace. 1280 1281config SYSCTL_ARCH_UNALIGN_NO_WARN 1282 bool 1283 help 1284 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1285 Allows arch to define/use @no_unaligned_warning to possibly warn 1286 about unaligned access emulation going on under the hood. 1287 1288config SYSCTL_ARCH_UNALIGN_ALLOW 1289 bool 1290 help 1291 Enable support for /proc/sys/kernel/unaligned-trap 1292 Allows arches to define/use @unaligned_enabled to runtime toggle 1293 the unaligned access emulation. 1294 see arch/parisc/kernel/unaligned.c for reference 1295 1296config HAVE_PCSPKR_PLATFORM 1297 bool 1298 1299menuconfig EXPERT 1300 bool "Configure standard kernel features (expert users)" 1301 # Unhide debug options, to make the on-by-default options visible 1302 select DEBUG_KERNEL 1303 help 1304 This option allows certain base kernel options and settings 1305 to be disabled or tweaked. This is for specialized 1306 environments which can tolerate a "non-standard" kernel. 1307 Only use this if you really know what you are doing. 1308 1309config UID16 1310 bool "Enable 16-bit UID system calls" if EXPERT 1311 depends on HAVE_UID16 1312 default y 1313 help 1314 This enables the legacy 16-bit UID syscall wrappers. 1315 1316config SGETMASK_SYSCALL 1317 bool "sgetmask/ssetmask syscalls support" if EXPERT 1318 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH 1319 ---help--- 1320 sys_sgetmask and sys_ssetmask are obsolete system calls 1321 no longer supported in libc but still enabled by default in some 1322 architectures. 1323 1324 If unsure, leave the default option here. 1325 1326config SYSFS_SYSCALL 1327 bool "Sysfs syscall support" if EXPERT 1328 default y 1329 ---help--- 1330 sys_sysfs is an obsolete system call no longer supported in libc. 1331 Note that disabling this option is more secure but might break 1332 compatibility with some systems. 1333 1334 If unsure say Y here. 1335 1336config SYSCTL_SYSCALL 1337 bool "Sysctl syscall support" if EXPERT 1338 depends on PROC_SYSCTL 1339 default n 1340 select SYSCTL 1341 ---help--- 1342 sys_sysctl uses binary paths that have been found challenging 1343 to properly maintain and use. The interface in /proc/sys 1344 using paths with ascii names is now the primary path to this 1345 information. 1346 1347 Almost nothing using the binary sysctl interface so if you are 1348 trying to save some space it is probably safe to disable this, 1349 making your kernel marginally smaller. 1350 1351 If unsure say N here. 1352 1353config KALLSYMS 1354 bool "Load all symbols for debugging/ksymoops" if EXPERT 1355 default y 1356 help 1357 Say Y here to let the kernel print out symbolic crash information and 1358 symbolic stack backtraces. This increases the size of the kernel 1359 somewhat, as all symbols have to be loaded into the kernel image. 1360 1361config KALLSYMS_ALL 1362 bool "Include all symbols in kallsyms" 1363 depends on DEBUG_KERNEL && KALLSYMS 1364 help 1365 Normally kallsyms only contains the symbols of functions for nicer 1366 OOPS messages and backtraces (i.e., symbols from the text and inittext 1367 sections). This is sufficient for most cases. And only in very rare 1368 cases (e.g., when a debugger is used) all symbols are required (e.g., 1369 names of variables from the data sections, etc). 1370 1371 This option makes sure that all symbols are loaded into the kernel 1372 image (i.e., symbols from all sections) in cost of increased kernel 1373 size (depending on the kernel configuration, it may be 300KiB or 1374 something like this). 1375 1376 Say N unless you really need all symbols. 1377 1378config PRINTK 1379 default y 1380 bool "Enable support for printk" if EXPERT 1381 select IRQ_WORK 1382 help 1383 This option enables normal printk support. Removing it 1384 eliminates most of the message strings from the kernel image 1385 and makes the kernel more or less silent. As this makes it 1386 very difficult to diagnose system problems, saying N here is 1387 strongly discouraged. 1388 1389config BUG 1390 bool "BUG() support" if EXPERT 1391 default y 1392 help 1393 Disabling this option eliminates support for BUG and WARN, reducing 1394 the size of your kernel image and potentially quietly ignoring 1395 numerous fatal conditions. You should only consider disabling this 1396 option for embedded systems with no facilities for reporting errors. 1397 Just say Y. 1398 1399config ELF_CORE 1400 depends on COREDUMP 1401 default y 1402 bool "Enable ELF core dumps" if EXPERT 1403 help 1404 Enable support for generating core dumps. Disabling saves about 4k. 1405 1406 1407config PCSPKR_PLATFORM 1408 bool "Enable PC-Speaker support" if EXPERT 1409 depends on HAVE_PCSPKR_PLATFORM 1410 select I8253_LOCK 1411 default y 1412 help 1413 This option allows to disable the internal PC-Speaker 1414 support, saving some memory. 1415 1416config BASE_FULL 1417 default y 1418 bool "Enable full-sized data structures for core" if EXPERT 1419 help 1420 Disabling this option reduces the size of miscellaneous core 1421 kernel data structures. This saves memory on small machines, 1422 but may reduce performance. 1423 1424config FUTEX 1425 bool "Enable futex support" if EXPERT 1426 default y 1427 select RT_MUTEXES 1428 help 1429 Disabling this option will cause the kernel to be built without 1430 support for "fast userspace mutexes". The resulting kernel may not 1431 run glibc-based applications correctly. 1432 1433config HAVE_FUTEX_CMPXCHG 1434 bool 1435 help 1436 Architectures should select this if futex_atomic_cmpxchg_inatomic() 1437 is implemented and always working. This removes a couple of runtime 1438 checks. 1439 1440config EPOLL 1441 bool "Enable eventpoll support" if EXPERT 1442 default y 1443 select ANON_INODES 1444 help 1445 Disabling this option will cause the kernel to be built without 1446 support for epoll family of system calls. 1447 1448config SIGNALFD 1449 bool "Enable signalfd() system call" if EXPERT 1450 select ANON_INODES 1451 default y 1452 help 1453 Enable the signalfd() system call that allows to receive signals 1454 on a file descriptor. 1455 1456 If unsure, say Y. 1457 1458config TIMERFD 1459 bool "Enable timerfd() system call" if EXPERT 1460 select ANON_INODES 1461 default y 1462 help 1463 Enable the timerfd() system call that allows to receive timer 1464 events on a file descriptor. 1465 1466 If unsure, say Y. 1467 1468config EVENTFD 1469 bool "Enable eventfd() system call" if EXPERT 1470 select ANON_INODES 1471 default y 1472 help 1473 Enable the eventfd() system call that allows to receive both 1474 kernel notification (ie. KAIO) or userspace notifications. 1475 1476 If unsure, say Y. 1477 1478config SHMEM 1479 bool "Use full shmem filesystem" if EXPERT 1480 default y 1481 depends on MMU 1482 help 1483 The shmem is an internal filesystem used to manage shared memory. 1484 It is backed by swap and manages resource limits. It is also exported 1485 to userspace as tmpfs if TMPFS is enabled. Disabling this 1486 option replaces shmem and tmpfs with the much simpler ramfs code, 1487 which may be appropriate on small systems without swap. 1488 1489config AIO 1490 bool "Enable AIO support" if EXPERT 1491 default y 1492 help 1493 This option enables POSIX asynchronous I/O which may by used 1494 by some high performance threaded applications. Disabling 1495 this option saves about 7k. 1496 1497config PCI_QUIRKS 1498 default y 1499 bool "Enable PCI quirk workarounds" if EXPERT 1500 depends on PCI 1501 help 1502 This enables workarounds for various PCI chipset 1503 bugs/quirks. Disable this only if your target machine is 1504 unaffected by PCI quirks. 1505 1506config EMBEDDED 1507 bool "Embedded system" 1508 option allnoconfig_y 1509 select EXPERT 1510 help 1511 This option should be enabled if compiling the kernel for 1512 an embedded system so certain expert options are available 1513 for configuration. 1514 1515config HAVE_PERF_EVENTS 1516 bool 1517 help 1518 See tools/perf/design.txt for details. 1519 1520config PERF_USE_VMALLOC 1521 bool 1522 help 1523 See tools/perf/design.txt for details 1524 1525menu "Kernel Performance Events And Counters" 1526 1527config PERF_EVENTS 1528 bool "Kernel performance events and counters" 1529 default y if PROFILING 1530 depends on HAVE_PERF_EVENTS 1531 select ANON_INODES 1532 select IRQ_WORK 1533 help 1534 Enable kernel support for various performance events provided 1535 by software and hardware. 1536 1537 Software events are supported either built-in or via the 1538 use of generic tracepoints. 1539 1540 Most modern CPUs support performance events via performance 1541 counter registers. These registers count the number of certain 1542 types of hw events: such as instructions executed, cachemisses 1543 suffered, or branches mis-predicted - without slowing down the 1544 kernel or applications. These registers can also trigger interrupts 1545 when a threshold number of events have passed - and can thus be 1546 used to profile the code that runs on that CPU. 1547 1548 The Linux Performance Event subsystem provides an abstraction of 1549 these software and hardware event capabilities, available via a 1550 system call and used by the "perf" utility in tools/perf/. It 1551 provides per task and per CPU counters, and it provides event 1552 capabilities on top of those. 1553 1554 Say Y if unsure. 1555 1556config DEBUG_PERF_USE_VMALLOC 1557 default n 1558 bool "Debug: use vmalloc to back perf mmap() buffers" 1559 depends on PERF_EVENTS && DEBUG_KERNEL 1560 select PERF_USE_VMALLOC 1561 help 1562 Use vmalloc memory to back perf mmap() buffers. 1563 1564 Mostly useful for debugging the vmalloc code on platforms 1565 that don't require it. 1566 1567 Say N if unsure. 1568 1569endmenu 1570 1571config VM_EVENT_COUNTERS 1572 default y 1573 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1574 help 1575 VM event counters are needed for event counts to be shown. 1576 This option allows the disabling of the VM event counters 1577 on EXPERT systems. /proc/vmstat will only show page counts 1578 if VM event counters are disabled. 1579 1580config SLUB_DEBUG 1581 default y 1582 bool "Enable SLUB debugging support" if EXPERT 1583 depends on SLUB && SYSFS 1584 help 1585 SLUB has extensive debug support features. Disabling these can 1586 result in significant savings in code size. This also disables 1587 SLUB sysfs support. /sys/slab will not exist and there will be 1588 no support for cache validation etc. 1589 1590config COMPAT_BRK 1591 bool "Disable heap randomization" 1592 default y 1593 help 1594 Randomizing heap placement makes heap exploits harder, but it 1595 also breaks ancient binaries (including anything libc5 based). 1596 This option changes the bootup default to heap randomization 1597 disabled, and can be overridden at runtime by setting 1598 /proc/sys/kernel/randomize_va_space to 2. 1599 1600 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1601 1602choice 1603 prompt "Choose SLAB allocator" 1604 default SLUB 1605 help 1606 This option allows to select a slab allocator. 1607 1608config SLAB 1609 bool "SLAB" 1610 help 1611 The regular slab allocator that is established and known to work 1612 well in all environments. It organizes cache hot objects in 1613 per cpu and per node queues. 1614 1615config SLUB 1616 bool "SLUB (Unqueued Allocator)" 1617 help 1618 SLUB is a slab allocator that minimizes cache line usage 1619 instead of managing queues of cached objects (SLAB approach). 1620 Per cpu caching is realized using slabs of objects instead 1621 of queues of objects. SLUB can use memory efficiently 1622 and has enhanced diagnostics. SLUB is the default choice for 1623 a slab allocator. 1624 1625config SLOB 1626 depends on EXPERT 1627 bool "SLOB (Simple Allocator)" 1628 help 1629 SLOB replaces the stock allocator with a drastically simpler 1630 allocator. SLOB is generally more space efficient but 1631 does not perform as well on large systems. 1632 1633endchoice 1634 1635config SLUB_CPU_PARTIAL 1636 default y 1637 depends on SLUB && SMP 1638 bool "SLUB per cpu partial cache" 1639 help 1640 Per cpu partial caches accellerate objects allocation and freeing 1641 that is local to a processor at the price of more indeterminism 1642 in the latency of the free. On overflow these caches will be cleared 1643 which requires the taking of locks that may cause latency spikes. 1644 Typically one would choose no for a realtime system. 1645 1646config MMAP_ALLOW_UNINITIALIZED 1647 bool "Allow mmapped anonymous memory to be uninitialized" 1648 depends on EXPERT && !MMU 1649 default n 1650 help 1651 Normally, and according to the Linux spec, anonymous memory obtained 1652 from mmap() has it's contents cleared before it is passed to 1653 userspace. Enabling this config option allows you to request that 1654 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1655 providing a huge performance boost. If this option is not enabled, 1656 then the flag will be ignored. 1657 1658 This is taken advantage of by uClibc's malloc(), and also by 1659 ELF-FDPIC binfmt's brk and stack allocator. 1660 1661 Because of the obvious security issues, this option should only be 1662 enabled on embedded devices where you control what is run in 1663 userspace. Since that isn't generally a problem on no-MMU systems, 1664 it is normally safe to say Y here. 1665 1666 See Documentation/nommu-mmap.txt for more information. 1667 1668config SYSTEM_TRUSTED_KEYRING 1669 bool "Provide system-wide ring of trusted keys" 1670 depends on KEYS 1671 help 1672 Provide a system keyring to which trusted keys can be added. Keys in 1673 the keyring are considered to be trusted. Keys may be added at will 1674 by the kernel from compiled-in data and from hardware key stores, but 1675 userspace may only add extra keys if those keys can be verified by 1676 keys already in the keyring. 1677 1678 Keys in this keyring are used by module signature checking. 1679 1680config PROFILING 1681 bool "Profiling support" 1682 help 1683 Say Y here to enable the extended profiling support mechanisms used 1684 by profilers such as OProfile. 1685 1686# 1687# Place an empty function call at each tracepoint site. Can be 1688# dynamically changed for a probe function. 1689# 1690config TRACEPOINTS 1691 bool 1692 1693source "arch/Kconfig" 1694 1695endmenu # General setup 1696 1697config HAVE_GENERIC_DMA_COHERENT 1698 bool 1699 default n 1700 1701config SLABINFO 1702 bool 1703 depends on PROC_FS 1704 depends on SLAB || SLUB_DEBUG 1705 default y 1706 1707config RT_MUTEXES 1708 boolean 1709 1710config BASE_SMALL 1711 int 1712 default 0 if BASE_FULL 1713 default 1 if !BASE_FULL 1714 1715menuconfig MODULES 1716 bool "Enable loadable module support" 1717 option modules 1718 help 1719 Kernel modules are small pieces of compiled code which can 1720 be inserted in the running kernel, rather than being 1721 permanently built into the kernel. You use the "modprobe" 1722 tool to add (and sometimes remove) them. If you say Y here, 1723 many parts of the kernel can be built as modules (by 1724 answering M instead of Y where indicated): this is most 1725 useful for infrequently used options which are not required 1726 for booting. For more information, see the man pages for 1727 modprobe, lsmod, modinfo, insmod and rmmod. 1728 1729 If you say Y here, you will need to run "make 1730 modules_install" to put the modules under /lib/modules/ 1731 where modprobe can find them (you may need to be root to do 1732 this). 1733 1734 If unsure, say Y. 1735 1736if MODULES 1737 1738config MODULE_FORCE_LOAD 1739 bool "Forced module loading" 1740 default n 1741 help 1742 Allow loading of modules without version information (ie. modprobe 1743 --force). Forced module loading sets the 'F' (forced) taint flag and 1744 is usually a really bad idea. 1745 1746config MODULE_UNLOAD 1747 bool "Module unloading" 1748 help 1749 Without this option you will not be able to unload any 1750 modules (note that some modules may not be unloadable 1751 anyway), which makes your kernel smaller, faster 1752 and simpler. If unsure, say Y. 1753 1754config MODULE_FORCE_UNLOAD 1755 bool "Forced module unloading" 1756 depends on MODULE_UNLOAD 1757 help 1758 This option allows you to force a module to unload, even if the 1759 kernel believes it is unsafe: the kernel will remove the module 1760 without waiting for anyone to stop using it (using the -f option to 1761 rmmod). This is mainly for kernel developers and desperate users. 1762 If unsure, say N. 1763 1764config MODVERSIONS 1765 bool "Module versioning support" 1766 help 1767 Usually, you have to use modules compiled with your kernel. 1768 Saying Y here makes it sometimes possible to use modules 1769 compiled for different kernels, by adding enough information 1770 to the modules to (hopefully) spot any changes which would 1771 make them incompatible with the kernel you are running. If 1772 unsure, say N. 1773 1774config MODULE_SRCVERSION_ALL 1775 bool "Source checksum for all modules" 1776 help 1777 Modules which contain a MODULE_VERSION get an extra "srcversion" 1778 field inserted into their modinfo section, which contains a 1779 sum of the source files which made it. This helps maintainers 1780 see exactly which source was used to build a module (since 1781 others sometimes change the module source without updating 1782 the version). With this option, such a "srcversion" field 1783 will be created for all modules. If unsure, say N. 1784 1785config MODULE_SIG 1786 bool "Module signature verification" 1787 depends on MODULES 1788 select SYSTEM_TRUSTED_KEYRING 1789 select KEYS 1790 select CRYPTO 1791 select ASYMMETRIC_KEY_TYPE 1792 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1793 select PUBLIC_KEY_ALGO_RSA 1794 select ASN1 1795 select OID_REGISTRY 1796 select X509_CERTIFICATE_PARSER 1797 help 1798 Check modules for valid signatures upon load: the signature 1799 is simply appended to the module. For more information see 1800 Documentation/module-signing.txt. 1801 1802 !!!WARNING!!! If you enable this option, you MUST make sure that the 1803 module DOES NOT get stripped after being signed. This includes the 1804 debuginfo strip done by some packagers (such as rpmbuild) and 1805 inclusion into an initramfs that wants the module size reduced. 1806 1807config MODULE_SIG_FORCE 1808 bool "Require modules to be validly signed" 1809 depends on MODULE_SIG 1810 help 1811 Reject unsigned modules or signed modules for which we don't have a 1812 key. Without this, such modules will simply taint the kernel. 1813 1814config MODULE_SIG_ALL 1815 bool "Automatically sign all modules" 1816 default y 1817 depends on MODULE_SIG 1818 help 1819 Sign all modules during make modules_install. Without this option, 1820 modules must be signed manually, using the scripts/sign-file tool. 1821 1822comment "Do not forget to sign required modules with scripts/sign-file" 1823 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1824 1825choice 1826 prompt "Which hash algorithm should modules be signed with?" 1827 depends on MODULE_SIG 1828 help 1829 This determines which sort of hashing algorithm will be used during 1830 signature generation. This algorithm _must_ be built into the kernel 1831 directly so that signature verification can take place. It is not 1832 possible to load a signed module containing the algorithm to check 1833 the signature on that module. 1834 1835config MODULE_SIG_SHA1 1836 bool "Sign modules with SHA-1" 1837 select CRYPTO_SHA1 1838 1839config MODULE_SIG_SHA224 1840 bool "Sign modules with SHA-224" 1841 select CRYPTO_SHA256 1842 1843config MODULE_SIG_SHA256 1844 bool "Sign modules with SHA-256" 1845 select CRYPTO_SHA256 1846 1847config MODULE_SIG_SHA384 1848 bool "Sign modules with SHA-384" 1849 select CRYPTO_SHA512 1850 1851config MODULE_SIG_SHA512 1852 bool "Sign modules with SHA-512" 1853 select CRYPTO_SHA512 1854 1855endchoice 1856 1857config MODULE_SIG_HASH 1858 string 1859 depends on MODULE_SIG 1860 default "sha1" if MODULE_SIG_SHA1 1861 default "sha224" if MODULE_SIG_SHA224 1862 default "sha256" if MODULE_SIG_SHA256 1863 default "sha384" if MODULE_SIG_SHA384 1864 default "sha512" if MODULE_SIG_SHA512 1865 1866endif # MODULES 1867 1868config INIT_ALL_POSSIBLE 1869 bool 1870 help 1871 Back when each arch used to define their own cpu_online_mask and 1872 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1873 with all 1s, and others with all 0s. When they were centralised, 1874 it was better to provide this option than to break all the archs 1875 and have several arch maintainers pursuing me down dark alleys. 1876 1877config STOP_MACHINE 1878 bool 1879 default y 1880 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1881 help 1882 Need stop_machine() primitive. 1883 1884source "block/Kconfig" 1885 1886config PREEMPT_NOTIFIERS 1887 bool 1888 1889config PADATA 1890 depends on SMP 1891 bool 1892 1893# Can be selected by architectures with broken toolchains 1894# that get confused by correct const<->read_only section 1895# mappings 1896config BROKEN_RODATA 1897 bool 1898 1899config ASN1 1900 tristate 1901 help 1902 Build a simple ASN.1 grammar compiler that produces a bytecode output 1903 that can be interpreted by the ASN.1 stream decoder and used to 1904 inform it as to what tags are to be expected in a stream and what 1905 functions to call on what tags. 1906 1907source "kernel/Kconfig.locks" 1908