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 HAVE_IRQ_WORK 24 bool 25 26config IRQ_WORK 27 bool 28 depends on HAVE_IRQ_WORK 29 30config BUILDTIME_EXTABLE_SORT 31 bool 32 33menu "General setup" 34 35config EXPERIMENTAL 36 bool "Prompt for development and/or incomplete code/drivers" 37 ---help--- 38 Some of the various things that Linux supports (such as network 39 drivers, file systems, network protocols, etc.) can be in a state 40 of development where the functionality, stability, or the level of 41 testing is not yet high enough for general use. This is usually 42 known as the "alpha-test" phase among developers. If a feature is 43 currently in alpha-test, then the developers usually discourage 44 uninformed widespread use of this feature by the general public to 45 avoid "Why doesn't this work?" type mail messages. However, active 46 testing and use of these systems is welcomed. Just be aware that it 47 may not meet the normal level of reliability or it may fail to work 48 in some special cases. Detailed bug reports from people familiar 49 with the kernel internals are usually welcomed by the developers 50 (before submitting bug reports, please read the documents 51 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, 52 <file:Documentation/BUG-HUNTING>, and 53 <file:Documentation/oops-tracing.txt> in the kernel source). 54 55 This option will also make obsoleted drivers available. These are 56 drivers that have been replaced by something else, and/or are 57 scheduled to be removed in a future kernel release. 58 59 Unless you intend to help test and develop a feature or driver that 60 falls into this category, or you have a situation that requires 61 using these features, you should probably say N here, which will 62 cause the configurator to present you with fewer choices. If 63 you say Y here, you will be offered the choice of using features or 64 drivers that are currently considered to be in the alpha-test phase. 65 66config BROKEN 67 bool 68 69config BROKEN_ON_SMP 70 bool 71 depends on BROKEN || !SMP 72 default y 73 74config INIT_ENV_ARG_LIMIT 75 int 76 default 32 if !UML 77 default 128 if UML 78 help 79 Maximum of each of the number of arguments and environment 80 variables passed to init from the kernel command line. 81 82 83config CROSS_COMPILE 84 string "Cross-compiler tool prefix" 85 help 86 Same as running 'make CROSS_COMPILE=prefix-' but stored for 87 default make runs in this kernel build directory. You don't 88 need to set this unless you want the configured kernel build 89 directory to select the cross-compiler automatically. 90 91config LOCALVERSION 92 string "Local version - append to kernel release" 93 help 94 Append an extra string to the end of your kernel version. 95 This will show up when you type uname, for example. 96 The string you set here will be appended after the contents of 97 any files with a filename matching localversion* in your 98 object and source tree, in that order. Your total string can 99 be a maximum of 64 characters. 100 101config LOCALVERSION_AUTO 102 bool "Automatically append version information to the version string" 103 default y 104 help 105 This will try to automatically determine if the current tree is a 106 release tree by looking for git tags that belong to the current 107 top of tree revision. 108 109 A string of the format -gxxxxxxxx will be added to the localversion 110 if a git-based tree is found. The string generated by this will be 111 appended after any matching localversion* files, and after the value 112 set in CONFIG_LOCALVERSION. 113 114 (The actual string used here is the first eight characters produced 115 by running the command: 116 117 $ git rev-parse --verify HEAD 118 119 which is done within the script "scripts/setlocalversion".) 120 121config HAVE_KERNEL_GZIP 122 bool 123 124config HAVE_KERNEL_BZIP2 125 bool 126 127config HAVE_KERNEL_LZMA 128 bool 129 130config HAVE_KERNEL_XZ 131 bool 132 133config HAVE_KERNEL_LZO 134 bool 135 136choice 137 prompt "Kernel compression mode" 138 default KERNEL_GZIP 139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO 140 help 141 The linux kernel is a kind of self-extracting executable. 142 Several compression algorithms are available, which differ 143 in efficiency, compression and decompression speed. 144 Compression speed is only relevant when building a kernel. 145 Decompression speed is relevant at each boot. 146 147 If you have any problems with bzip2 or lzma compressed 148 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 149 version of this functionality (bzip2 only), for 2.4, was 150 supplied by Christian Ludwig) 151 152 High compression options are mostly useful for users, who 153 are low on disk space (embedded systems), but for whom ram 154 size matters less. 155 156 If in doubt, select 'gzip' 157 158config KERNEL_GZIP 159 bool "Gzip" 160 depends on HAVE_KERNEL_GZIP 161 help 162 The old and tried gzip compression. It provides a good balance 163 between compression ratio and decompression speed. 164 165config KERNEL_BZIP2 166 bool "Bzip2" 167 depends on HAVE_KERNEL_BZIP2 168 help 169 Its compression ratio and speed is intermediate. 170 Decompression speed is slowest among the choices. The kernel 171 size is about 10% smaller with bzip2, in comparison to gzip. 172 Bzip2 uses a large amount of memory. For modern kernels you 173 will need at least 8MB RAM or more for booting. 174 175config KERNEL_LZMA 176 bool "LZMA" 177 depends on HAVE_KERNEL_LZMA 178 help 179 This compression algorithm's ratio is best. Decompression speed 180 is between gzip and bzip2. Compression is slowest. 181 The kernel size is about 33% smaller with LZMA in comparison to gzip. 182 183config KERNEL_XZ 184 bool "XZ" 185 depends on HAVE_KERNEL_XZ 186 help 187 XZ uses the LZMA2 algorithm and instruction set specific 188 BCJ filters which can improve compression ratio of executable 189 code. The size of the kernel is about 30% smaller with XZ in 190 comparison to gzip. On architectures for which there is a BCJ 191 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 192 will create a few percent smaller kernel than plain LZMA. 193 194 The speed is about the same as with LZMA: The decompression 195 speed of XZ is better than that of bzip2 but worse than gzip 196 and LZO. Compression is slow. 197 198config KERNEL_LZO 199 bool "LZO" 200 depends on HAVE_KERNEL_LZO 201 help 202 Its compression ratio is the poorest among the choices. The kernel 203 size is about 10% bigger than gzip; however its speed 204 (both compression and decompression) is the fastest. 205 206endchoice 207 208config DEFAULT_HOSTNAME 209 string "Default hostname" 210 default "(none)" 211 help 212 This option determines the default system hostname before userspace 213 calls sethostname(2). The kernel traditionally uses "(none)" here, 214 but you may wish to use a different default here to make a minimal 215 system more usable with less configuration. 216 217config SWAP 218 bool "Support for paging of anonymous memory (swap)" 219 depends on MMU && BLOCK 220 default y 221 help 222 This option allows you to choose whether you want to have support 223 for so called swap devices or swap files in your kernel that are 224 used to provide more virtual memory than the actual RAM present 225 in your computer. If unsure say Y. 226 227config SYSVIPC 228 bool "System V IPC" 229 ---help--- 230 Inter Process Communication is a suite of library functions and 231 system calls which let processes (running programs) synchronize and 232 exchange information. It is generally considered to be a good thing, 233 and some programs won't run unless you say Y here. In particular, if 234 you want to run the DOS emulator dosemu under Linux (read the 235 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 236 you'll need to say Y here. 237 238 You can find documentation about IPC with "info ipc" and also in 239 section 6.4 of the Linux Programmer's Guide, available from 240 <http://www.tldp.org/guides.html>. 241 242config SYSVIPC_SYSCTL 243 bool 244 depends on SYSVIPC 245 depends on SYSCTL 246 default y 247 248config POSIX_MQUEUE 249 bool "POSIX Message Queues" 250 depends on NET && EXPERIMENTAL 251 ---help--- 252 POSIX variant of message queues is a part of IPC. In POSIX message 253 queues every message has a priority which decides about succession 254 of receiving it by a process. If you want to compile and run 255 programs written e.g. for Solaris with use of its POSIX message 256 queues (functions mq_*) say Y here. 257 258 POSIX message queues are visible as a filesystem called 'mqueue' 259 and can be mounted somewhere if you want to do filesystem 260 operations on message queues. 261 262 If unsure, say Y. 263 264config POSIX_MQUEUE_SYSCTL 265 bool 266 depends on POSIX_MQUEUE 267 depends on SYSCTL 268 default y 269 270config FHANDLE 271 bool "open by fhandle syscalls" 272 select EXPORTFS 273 help 274 If you say Y here, a user level program will be able to map 275 file names to handle and then later use the handle for 276 different file system operations. This is useful in implementing 277 userspace file servers, which now track files using handles instead 278 of names. The handle would remain the same even if file names 279 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 280 syscalls. 281 282config AUDIT 283 bool "Auditing support" 284 depends on NET 285 help 286 Enable auditing infrastructure that can be used with another 287 kernel subsystem, such as SELinux (which requires this for 288 logging of avc messages output). Does not do system-call 289 auditing without CONFIG_AUDITSYSCALL. 290 291config AUDITSYSCALL 292 bool "Enable system-call auditing support" 293 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT)) 294 default y if SECURITY_SELINUX 295 help 296 Enable low-overhead system-call auditing infrastructure that 297 can be used independently or with another kernel subsystem, 298 such as SELinux. 299 300config AUDIT_WATCH 301 def_bool y 302 depends on AUDITSYSCALL 303 select FSNOTIFY 304 305config AUDIT_TREE 306 def_bool y 307 depends on AUDITSYSCALL 308 select FSNOTIFY 309 310config AUDIT_LOGINUID_IMMUTABLE 311 bool "Make audit loginuid immutable" 312 depends on AUDIT 313 help 314 The config option toggles if a task setting its loginuid requires 315 CAP_SYS_AUDITCONTROL or if that task should require no special permissions 316 but should instead only allow setting its loginuid if it was never 317 previously set. On systems which use systemd or a similar central 318 process to restart login services this should be set to true. On older 319 systems in which an admin would typically have to directly stop and 320 start processes this should be set to false. Setting this to true allows 321 one to drop potentially dangerous capabilites from the login tasks, 322 but may not be backwards compatible with older init systems. 323 324source "kernel/irq/Kconfig" 325source "kernel/time/Kconfig" 326 327menu "CPU/Task time and stats accounting" 328 329choice 330 prompt "Cputime accounting" 331 default TICK_CPU_ACCOUNTING if !PPC64 332 default VIRT_CPU_ACCOUNTING if PPC64 333 334# Kind of a stub config for the pure tick based cputime accounting 335config TICK_CPU_ACCOUNTING 336 bool "Simple tick based cputime accounting" 337 depends on !S390 338 help 339 This is the basic tick based cputime accounting that maintains 340 statistics about user, system and idle time spent on per jiffies 341 granularity. 342 343 If unsure, say Y. 344 345config VIRT_CPU_ACCOUNTING 346 bool "Deterministic task and CPU time accounting" 347 depends on HAVE_VIRT_CPU_ACCOUNTING 348 help 349 Select this option to enable more accurate task and CPU time 350 accounting. This is done by reading a CPU counter on each 351 kernel entry and exit and on transitions within the kernel 352 between system, softirq and hardirq state, so there is a 353 small performance impact. In the case of s390 or IBM POWER > 5, 354 this also enables accounting of stolen time on logically-partitioned 355 systems. 356 357config IRQ_TIME_ACCOUNTING 358 bool "Fine granularity task level IRQ time accounting" 359 depends on HAVE_IRQ_TIME_ACCOUNTING 360 help 361 Select this option to enable fine granularity task irq time 362 accounting. This is done by reading a timestamp on each 363 transitions between softirq and hardirq state, so there can be a 364 small performance impact. 365 366 If in doubt, say N here. 367 368endchoice 369 370config BSD_PROCESS_ACCT 371 bool "BSD Process Accounting" 372 help 373 If you say Y here, a user level program will be able to instruct the 374 kernel (via a special system call) to write process accounting 375 information to a file: whenever a process exits, information about 376 that process will be appended to the file by the kernel. The 377 information includes things such as creation time, owning user, 378 command name, memory usage, controlling terminal etc. (the complete 379 list is in the struct acct in <file:include/linux/acct.h>). It is 380 up to the user level program to do useful things with this 381 information. This is generally a good idea, so say Y. 382 383config BSD_PROCESS_ACCT_V3 384 bool "BSD Process Accounting version 3 file format" 385 depends on BSD_PROCESS_ACCT 386 default n 387 help 388 If you say Y here, the process accounting information is written 389 in a new file format that also logs the process IDs of each 390 process and it's parent. Note that this file format is incompatible 391 with previous v0/v1/v2 file formats, so you will need updated tools 392 for processing it. A preliminary version of these tools is available 393 at <http://www.gnu.org/software/acct/>. 394 395config TASKSTATS 396 bool "Export task/process statistics through netlink (EXPERIMENTAL)" 397 depends on NET 398 default n 399 help 400 Export selected statistics for tasks/processes through the 401 generic netlink interface. Unlike BSD process accounting, the 402 statistics are available during the lifetime of tasks/processes as 403 responses to commands. Like BSD accounting, they are sent to user 404 space on task exit. 405 406 Say N if unsure. 407 408config TASK_DELAY_ACCT 409 bool "Enable per-task delay accounting (EXPERIMENTAL)" 410 depends on TASKSTATS 411 help 412 Collect information on time spent by a task waiting for system 413 resources like cpu, synchronous block I/O completion and swapping 414 in pages. Such statistics can help in setting a task's priorities 415 relative to other tasks for cpu, io, rss limits etc. 416 417 Say N if unsure. 418 419config TASK_XACCT 420 bool "Enable extended accounting over taskstats (EXPERIMENTAL)" 421 depends on TASKSTATS 422 help 423 Collect extended task accounting data and send the data 424 to userland for processing over the taskstats interface. 425 426 Say N if unsure. 427 428config TASK_IO_ACCOUNTING 429 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" 430 depends on TASK_XACCT 431 help 432 Collect information on the number of bytes of storage I/O which this 433 task has caused. 434 435 Say N if unsure. 436 437endmenu # "CPU/Task time and stats accounting" 438 439menu "RCU Subsystem" 440 441choice 442 prompt "RCU Implementation" 443 default TREE_RCU 444 445config TREE_RCU 446 bool "Tree-based hierarchical RCU" 447 depends on !PREEMPT && SMP 448 help 449 This option selects the RCU implementation that is 450 designed for very large SMP system with hundreds or 451 thousands of CPUs. It also scales down nicely to 452 smaller systems. 453 454config TREE_PREEMPT_RCU 455 bool "Preemptible tree-based hierarchical RCU" 456 depends on PREEMPT && SMP 457 help 458 This option selects the RCU implementation that is 459 designed for very large SMP systems with hundreds or 460 thousands of CPUs, but for which real-time response 461 is also required. It also scales down nicely to 462 smaller systems. 463 464config TINY_RCU 465 bool "UP-only small-memory-footprint RCU" 466 depends on !PREEMPT && !SMP 467 help 468 This option selects the RCU implementation that is 469 designed for UP systems from which real-time response 470 is not required. This option greatly reduces the 471 memory footprint of RCU. 472 473config TINY_PREEMPT_RCU 474 bool "Preemptible UP-only small-memory-footprint RCU" 475 depends on PREEMPT && !SMP 476 help 477 This option selects the RCU implementation that is designed 478 for real-time UP systems. This option greatly reduces the 479 memory footprint of RCU. 480 481endchoice 482 483config PREEMPT_RCU 484 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU ) 485 help 486 This option enables preemptible-RCU code that is common between 487 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 488 489config RCU_USER_QS 490 bool "Consider userspace as in RCU extended quiescent state" 491 depends on HAVE_RCU_USER_QS && SMP 492 help 493 This option sets hooks on kernel / userspace boundaries and 494 puts RCU in extended quiescent state when the CPU runs in 495 userspace. It means that when a CPU runs in userspace, it is 496 excluded from the global RCU state machine and thus doesn't 497 to keep the timer tick on for RCU. 498 499 Unless you want to hack and help the development of the full 500 tickless feature, you shouldn't enable this option. It adds 501 unnecessary overhead. 502 503 If unsure say N 504 505config RCU_USER_QS_FORCE 506 bool "Force userspace extended QS by default" 507 depends on RCU_USER_QS 508 help 509 Set the hooks in user/kernel boundaries by default in order to 510 test this feature that treats userspace as an extended quiescent 511 state until we have a real user like a full adaptive nohz option. 512 513 Unless you want to hack and help the development of the full 514 tickless feature, you shouldn't enable this option. It adds 515 unnecessary overhead. 516 517 If unsure say N 518 519config RCU_FANOUT 520 int "Tree-based hierarchical RCU fanout value" 521 range 2 64 if 64BIT 522 range 2 32 if !64BIT 523 depends on TREE_RCU || TREE_PREEMPT_RCU 524 default 64 if 64BIT 525 default 32 if !64BIT 526 help 527 This option controls the fanout of hierarchical implementations 528 of RCU, allowing RCU to work efficiently on machines with 529 large numbers of CPUs. This value must be at least the fourth 530 root of NR_CPUS, which allows NR_CPUS to be insanely large. 531 The default value of RCU_FANOUT should be used for production 532 systems, but if you are stress-testing the RCU implementation 533 itself, small RCU_FANOUT values allow you to test large-system 534 code paths on small(er) systems. 535 536 Select a specific number if testing RCU itself. 537 Take the default if unsure. 538 539config RCU_FANOUT_LEAF 540 int "Tree-based hierarchical RCU leaf-level fanout value" 541 range 2 RCU_FANOUT if 64BIT 542 range 2 RCU_FANOUT if !64BIT 543 depends on TREE_RCU || TREE_PREEMPT_RCU 544 default 16 545 help 546 This option controls the leaf-level fanout of hierarchical 547 implementations of RCU, and allows trading off cache misses 548 against lock contention. Systems that synchronize their 549 scheduling-clock interrupts for energy-efficiency reasons will 550 want the default because the smaller leaf-level fanout keeps 551 lock contention levels acceptably low. Very large systems 552 (hundreds or thousands of CPUs) will instead want to set this 553 value to the maximum value possible in order to reduce the 554 number of cache misses incurred during RCU's grace-period 555 initialization. These systems tend to run CPU-bound, and thus 556 are not helped by synchronized interrupts, and thus tend to 557 skew them, which reduces lock contention enough that large 558 leaf-level fanouts work well. 559 560 Select a specific number if testing RCU itself. 561 562 Select the maximum permissible value for large systems. 563 564 Take the default if unsure. 565 566config RCU_FANOUT_EXACT 567 bool "Disable tree-based hierarchical RCU auto-balancing" 568 depends on TREE_RCU || TREE_PREEMPT_RCU 569 default n 570 help 571 This option forces use of the exact RCU_FANOUT value specified, 572 regardless of imbalances in the hierarchy. This is useful for 573 testing RCU itself, and might one day be useful on systems with 574 strong NUMA behavior. 575 576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 577 578 Say N if unsure. 579 580config RCU_FAST_NO_HZ 581 bool "Accelerate last non-dyntick-idle CPU's grace periods" 582 depends on NO_HZ && SMP 583 default n 584 help 585 This option causes RCU to attempt to accelerate grace periods 586 in order to allow CPUs to enter dynticks-idle state more 587 quickly. On the other hand, this option increases the overhead 588 of the dynticks-idle checking, particularly on systems with 589 large numbers of CPUs. 590 591 Say Y if energy efficiency is critically important, particularly 592 if you have relatively few CPUs. 593 594 Say N if you are unsure. 595 596config TREE_RCU_TRACE 597 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 598 select DEBUG_FS 599 help 600 This option provides tracing for the TREE_RCU and 601 TREE_PREEMPT_RCU implementations, permitting Makefile to 602 trivially select kernel/rcutree_trace.c. 603 604config RCU_BOOST 605 bool "Enable RCU priority boosting" 606 depends on RT_MUTEXES && PREEMPT_RCU 607 default n 608 help 609 This option boosts the priority of preempted RCU readers that 610 block the current preemptible RCU grace period for too long. 611 This option also prevents heavy loads from blocking RCU 612 callback invocation for all flavors of RCU. 613 614 Say Y here if you are working with real-time apps or heavy loads 615 Say N here if you are unsure. 616 617config RCU_BOOST_PRIO 618 int "Real-time priority to boost RCU readers to" 619 range 1 99 620 depends on RCU_BOOST 621 default 1 622 help 623 This option specifies the real-time priority to which long-term 624 preempted RCU readers are to be boosted. If you are working 625 with a real-time application that has one or more CPU-bound 626 threads running at a real-time priority level, you should set 627 RCU_BOOST_PRIO to a priority higher then the highest-priority 628 real-time CPU-bound thread. The default RCU_BOOST_PRIO value 629 of 1 is appropriate in the common case, which is real-time 630 applications that do not have any CPU-bound threads. 631 632 Some real-time applications might not have a single real-time 633 thread that saturates a given CPU, but instead might have 634 multiple real-time threads that, taken together, fully utilize 635 that CPU. In this case, you should set RCU_BOOST_PRIO to 636 a priority higher than the lowest-priority thread that is 637 conspiring to prevent the CPU from running any non-real-time 638 tasks. For example, if one thread at priority 10 and another 639 thread at priority 5 are between themselves fully consuming 640 the CPU time on a given CPU, then RCU_BOOST_PRIO should be 641 set to priority 6 or higher. 642 643 Specify the real-time priority, or take the default if unsure. 644 645config RCU_BOOST_DELAY 646 int "Milliseconds to delay boosting after RCU grace-period start" 647 range 0 3000 648 depends on RCU_BOOST 649 default 500 650 help 651 This option specifies the time to wait after the beginning of 652 a given grace period before priority-boosting preempted RCU 653 readers blocking that grace period. Note that any RCU reader 654 blocking an expedited RCU grace period is boosted immediately. 655 656 Accept the default if unsure. 657 658endmenu # "RCU Subsystem" 659 660config IKCONFIG 661 tristate "Kernel .config support" 662 ---help--- 663 This option enables the complete Linux kernel ".config" file 664 contents to be saved in the kernel. It provides documentation 665 of which kernel options are used in a running kernel or in an 666 on-disk kernel. This information can be extracted from the kernel 667 image file with the script scripts/extract-ikconfig and used as 668 input to rebuild the current kernel or to build another kernel. 669 It can also be extracted from a running kernel by reading 670 /proc/config.gz if enabled (below). 671 672config IKCONFIG_PROC 673 bool "Enable access to .config through /proc/config.gz" 674 depends on IKCONFIG && PROC_FS 675 ---help--- 676 This option enables access to the kernel configuration file 677 through /proc/config.gz. 678 679config LOG_BUF_SHIFT 680 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 681 range 12 21 682 default 17 683 help 684 Select kernel log buffer size as a power of 2. 685 Examples: 686 17 => 128 KB 687 16 => 64 KB 688 15 => 32 KB 689 14 => 16 KB 690 13 => 8 KB 691 12 => 4 KB 692 693# 694# Architectures with an unreliable sched_clock() should select this: 695# 696config HAVE_UNSTABLE_SCHED_CLOCK 697 bool 698 699menuconfig CGROUPS 700 boolean "Control Group support" 701 depends on EVENTFD 702 help 703 This option adds support for grouping sets of processes together, for 704 use with process control subsystems such as Cpusets, CFS, memory 705 controls or device isolation. 706 See 707 - Documentation/scheduler/sched-design-CFS.txt (CFS) 708 - Documentation/cgroups/ (features for grouping, isolation 709 and resource control) 710 711 Say N if unsure. 712 713if CGROUPS 714 715config CGROUP_DEBUG 716 bool "Example debug cgroup subsystem" 717 default n 718 help 719 This option enables a simple cgroup subsystem that 720 exports useful debugging information about the cgroups 721 framework. 722 723 Say N if unsure. 724 725config CGROUP_FREEZER 726 bool "Freezer cgroup subsystem" 727 help 728 Provides a way to freeze and unfreeze all tasks in a 729 cgroup. 730 731config CGROUP_DEVICE 732 bool "Device controller for cgroups" 733 help 734 Provides a cgroup implementing whitelists for devices which 735 a process in the cgroup can mknod or open. 736 737config CPUSETS 738 bool "Cpuset support" 739 help 740 This option will let you create and manage CPUSETs which 741 allow dynamically partitioning a system into sets of CPUs and 742 Memory Nodes and assigning tasks to run only within those sets. 743 This is primarily useful on large SMP or NUMA systems. 744 745 Say N if unsure. 746 747config PROC_PID_CPUSET 748 bool "Include legacy /proc/<pid>/cpuset file" 749 depends on CPUSETS 750 default y 751 752config CGROUP_CPUACCT 753 bool "Simple CPU accounting cgroup subsystem" 754 help 755 Provides a simple Resource Controller for monitoring the 756 total CPU consumed by the tasks in a cgroup. 757 758config RESOURCE_COUNTERS 759 bool "Resource counters" 760 help 761 This option enables controller independent resource accounting 762 infrastructure that works with cgroups. 763 764config MEMCG 765 bool "Memory Resource Controller for Control Groups" 766 depends on RESOURCE_COUNTERS 767 select MM_OWNER 768 help 769 Provides a memory resource controller that manages both anonymous 770 memory and page cache. (See Documentation/cgroups/memory.txt) 771 772 Note that setting this option increases fixed memory overhead 773 associated with each page of memory in the system. By this, 774 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 775 usage tracking struct at boot. Total amount of this is printed out 776 at boot. 777 778 Only enable when you're ok with these trade offs and really 779 sure you need the memory resource controller. Even when you enable 780 this, you can set "cgroup_disable=memory" at your boot option to 781 disable memory resource controller and you can avoid overheads. 782 (and lose benefits of memory resource controller) 783 784 This config option also selects MM_OWNER config option, which 785 could in turn add some fork/exit overhead. 786 787config MEMCG_SWAP 788 bool "Memory Resource Controller Swap Extension" 789 depends on MEMCG && SWAP 790 help 791 Add swap management feature to memory resource controller. When you 792 enable this, you can limit mem+swap usage per cgroup. In other words, 793 when you disable this, memory resource controller has no cares to 794 usage of swap...a process can exhaust all of the swap. This extension 795 is useful when you want to avoid exhaustion swap but this itself 796 adds more overheads and consumes memory for remembering information. 797 Especially if you use 32bit system or small memory system, please 798 be careful about enabling this. When memory resource controller 799 is disabled by boot option, this will be automatically disabled and 800 there will be no overhead from this. Even when you set this config=y, 801 if boot option "swapaccount=0" is set, swap will not be accounted. 802 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 803 size is 4096bytes, 512k per 1Gbytes of swap. 804config MEMCG_SWAP_ENABLED 805 bool "Memory Resource Controller Swap Extension enabled by default" 806 depends on MEMCG_SWAP 807 default y 808 help 809 Memory Resource Controller Swap Extension comes with its price in 810 a bigger memory consumption. General purpose distribution kernels 811 which want to enable the feature but keep it disabled by default 812 and let the user enable it by swapaccount boot command line 813 parameter should have this option unselected. 814 For those who want to have the feature enabled by default should 815 select this option (if, for some reason, they need to disable it 816 then swapaccount=0 does the trick). 817config MEMCG_KMEM 818 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)" 819 depends on MEMCG && EXPERIMENTAL 820 default n 821 help 822 The Kernel Memory extension for Memory Resource Controller can limit 823 the amount of memory used by kernel objects in the system. Those are 824 fundamentally different from the entities handled by the standard 825 Memory Controller, which are page-based, and can be swapped. Users of 826 the kmem extension can use it to guarantee that no group of processes 827 will ever exhaust kernel resources alone. 828 829config CGROUP_HUGETLB 830 bool "HugeTLB Resource Controller for Control Groups" 831 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL 832 default n 833 help 834 Provides a cgroup Resource Controller for HugeTLB pages. 835 When you enable this, you can put a per cgroup limit on HugeTLB usage. 836 The limit is enforced during page fault. Since HugeTLB doesn't 837 support page reclaim, enforcing the limit at page fault time implies 838 that, the application will get SIGBUS signal if it tries to access 839 HugeTLB pages beyond its limit. This requires the application to know 840 beforehand how much HugeTLB pages it would require for its use. The 841 control group is tracked in the third page lru pointer. This means 842 that we cannot use the controller with huge page less than 3 pages. 843 844config CGROUP_PERF 845 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 846 depends on PERF_EVENTS && CGROUPS 847 help 848 This option extends the per-cpu mode to restrict monitoring to 849 threads which belong to the cgroup specified and run on the 850 designated cpu. 851 852 Say N if unsure. 853 854menuconfig CGROUP_SCHED 855 bool "Group CPU scheduler" 856 default n 857 help 858 This feature lets CPU scheduler recognize task groups and control CPU 859 bandwidth allocation to such task groups. It uses cgroups to group 860 tasks. 861 862if CGROUP_SCHED 863config FAIR_GROUP_SCHED 864 bool "Group scheduling for SCHED_OTHER" 865 depends on CGROUP_SCHED 866 default CGROUP_SCHED 867 868config CFS_BANDWIDTH 869 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 870 depends on EXPERIMENTAL 871 depends on FAIR_GROUP_SCHED 872 default n 873 help 874 This option allows users to define CPU bandwidth rates (limits) for 875 tasks running within the fair group scheduler. Groups with no limit 876 set are considered to be unconstrained and will run with no 877 restriction. 878 See tip/Documentation/scheduler/sched-bwc.txt for more information. 879 880config RT_GROUP_SCHED 881 bool "Group scheduling for SCHED_RR/FIFO" 882 depends on EXPERIMENTAL 883 depends on CGROUP_SCHED 884 default n 885 help 886 This feature lets you explicitly allocate real CPU bandwidth 887 to task groups. If enabled, it will also make it impossible to 888 schedule realtime tasks for non-root users until you allocate 889 realtime bandwidth for them. 890 See Documentation/scheduler/sched-rt-group.txt for more information. 891 892endif #CGROUP_SCHED 893 894config BLK_CGROUP 895 bool "Block IO controller" 896 depends on BLOCK 897 default n 898 ---help--- 899 Generic block IO controller cgroup interface. This is the common 900 cgroup interface which should be used by various IO controlling 901 policies. 902 903 Currently, CFQ IO scheduler uses it to recognize task groups and 904 control disk bandwidth allocation (proportional time slice allocation) 905 to such task groups. It is also used by bio throttling logic in 906 block layer to implement upper limit in IO rates on a device. 907 908 This option only enables generic Block IO controller infrastructure. 909 One needs to also enable actual IO controlling logic/policy. For 910 enabling proportional weight division of disk bandwidth in CFQ, set 911 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 912 CONFIG_BLK_DEV_THROTTLING=y. 913 914 See Documentation/cgroups/blkio-controller.txt for more information. 915 916config DEBUG_BLK_CGROUP 917 bool "Enable Block IO controller debugging" 918 depends on BLK_CGROUP 919 default n 920 ---help--- 921 Enable some debugging help. Currently it exports additional stat 922 files in a cgroup which can be useful for debugging. 923 924endif # CGROUPS 925 926config CHECKPOINT_RESTORE 927 bool "Checkpoint/restore support" if EXPERT 928 default n 929 help 930 Enables additional kernel features in a sake of checkpoint/restore. 931 In particular it adds auxiliary prctl codes to setup process text, 932 data and heap segment sizes, and a few additional /proc filesystem 933 entries. 934 935 If unsure, say N here. 936 937menuconfig NAMESPACES 938 bool "Namespaces support" if EXPERT 939 default !EXPERT 940 help 941 Provides the way to make tasks work with different objects using 942 the same id. For example same IPC id may refer to different objects 943 or same user id or pid may refer to different tasks when used in 944 different namespaces. 945 946if NAMESPACES 947 948config UTS_NS 949 bool "UTS namespace" 950 default y 951 help 952 In this namespace tasks see different info provided with the 953 uname() system call 954 955config IPC_NS 956 bool "IPC namespace" 957 depends on (SYSVIPC || POSIX_MQUEUE) 958 default y 959 help 960 In this namespace tasks work with IPC ids which correspond to 961 different IPC objects in different namespaces. 962 963config USER_NS 964 bool "User namespace (EXPERIMENTAL)" 965 depends on EXPERIMENTAL 966 depends on UIDGID_CONVERTED 967 select UIDGID_STRICT_TYPE_CHECKS 968 969 default n 970 help 971 This allows containers, i.e. vservers, to use user namespaces 972 to provide different user info for different servers. 973 If unsure, say N. 974 975config PID_NS 976 bool "PID Namespaces" 977 default y 978 help 979 Support process id namespaces. This allows having multiple 980 processes with the same pid as long as they are in different 981 pid namespaces. This is a building block of containers. 982 983config NET_NS 984 bool "Network namespace" 985 depends on NET 986 default y 987 help 988 Allow user space to create what appear to be multiple instances 989 of the network stack. 990 991endif # NAMESPACES 992 993config UIDGID_CONVERTED 994 # True if all of the selected software conmponents are known 995 # to have uid_t and gid_t converted to kuid_t and kgid_t 996 # where appropriate and are otherwise safe to use with 997 # the user namespace. 998 bool 999 default y 1000 1001 # Networking 1002 depends on NET_9P = n 1003 1004 # Filesystems 1005 depends on 9P_FS = n 1006 depends on AFS_FS = n 1007 depends on AUTOFS4_FS = n 1008 depends on CEPH_FS = n 1009 depends on CIFS = n 1010 depends on CODA_FS = n 1011 depends on FUSE_FS = n 1012 depends on GFS2_FS = n 1013 depends on NCP_FS = n 1014 depends on NFSD = n 1015 depends on NFS_FS = n 1016 depends on OCFS2_FS = n 1017 depends on XFS_FS = n 1018 1019config UIDGID_STRICT_TYPE_CHECKS 1020 bool "Require conversions between uid/gids and their internal representation" 1021 depends on UIDGID_CONVERTED 1022 default n 1023 help 1024 While the nececessary conversions are being added to all subsystems this option allows 1025 the code to continue to build for unconverted subsystems. 1026 1027 Say Y here if you want the strict type checking enabled 1028 1029config SCHED_AUTOGROUP 1030 bool "Automatic process group scheduling" 1031 select EVENTFD 1032 select CGROUPS 1033 select CGROUP_SCHED 1034 select FAIR_GROUP_SCHED 1035 help 1036 This option optimizes the scheduler for common desktop workloads by 1037 automatically creating and populating task groups. This separation 1038 of workloads isolates aggressive CPU burners (like build jobs) from 1039 desktop applications. Task group autogeneration is currently based 1040 upon task session. 1041 1042config MM_OWNER 1043 bool 1044 1045config SYSFS_DEPRECATED 1046 bool "Enable deprecated sysfs features to support old userspace tools" 1047 depends on SYSFS 1048 default n 1049 help 1050 This option adds code that switches the layout of the "block" class 1051 devices, to not show up in /sys/class/block/, but only in 1052 /sys/block/. 1053 1054 This switch is only active when the sysfs.deprecated=1 boot option is 1055 passed or the SYSFS_DEPRECATED_V2 option is set. 1056 1057 This option allows new kernels to run on old distributions and tools, 1058 which might get confused by /sys/class/block/. Since 2007/2008 all 1059 major distributions and tools handle this just fine. 1060 1061 Recent distributions and userspace tools after 2009/2010 depend on 1062 the existence of /sys/class/block/, and will not work with this 1063 option enabled. 1064 1065 Only if you are using a new kernel on an old distribution, you might 1066 need to say Y here. 1067 1068config SYSFS_DEPRECATED_V2 1069 bool "Enable deprecated sysfs features by default" 1070 default n 1071 depends on SYSFS 1072 depends on SYSFS_DEPRECATED 1073 help 1074 Enable deprecated sysfs by default. 1075 1076 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1077 option. 1078 1079 Only if you are using a new kernel on an old distribution, you might 1080 need to say Y here. Even then, odds are you would not need it 1081 enabled, you can always pass the boot option if absolutely necessary. 1082 1083config RELAY 1084 bool "Kernel->user space relay support (formerly relayfs)" 1085 help 1086 This option enables support for relay interface support in 1087 certain file systems (such as debugfs). 1088 It is designed to provide an efficient mechanism for tools and 1089 facilities to relay large amounts of data from kernel space to 1090 user space. 1091 1092 If unsure, say N. 1093 1094config BLK_DEV_INITRD 1095 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1096 depends on BROKEN || !FRV 1097 help 1098 The initial RAM filesystem is a ramfs which is loaded by the 1099 boot loader (loadlin or lilo) and that is mounted as root 1100 before the normal boot procedure. It is typically used to 1101 load modules needed to mount the "real" root file system, 1102 etc. See <file:Documentation/initrd.txt> for details. 1103 1104 If RAM disk support (BLK_DEV_RAM) is also included, this 1105 also enables initial RAM disk (initrd) support and adds 1106 15 Kbytes (more on some other architectures) to the kernel size. 1107 1108 If unsure say Y. 1109 1110if BLK_DEV_INITRD 1111 1112source "usr/Kconfig" 1113 1114endif 1115 1116config CC_OPTIMIZE_FOR_SIZE 1117 bool "Optimize for size" 1118 help 1119 Enabling this option will pass "-Os" instead of "-O2" to gcc 1120 resulting in a smaller kernel. 1121 1122 If unsure, say Y. 1123 1124config SYSCTL 1125 bool 1126 1127config ANON_INODES 1128 bool 1129 1130menuconfig EXPERT 1131 bool "Configure standard kernel features (expert users)" 1132 # Unhide debug options, to make the on-by-default options visible 1133 select DEBUG_KERNEL 1134 help 1135 This option allows certain base kernel options and settings 1136 to be disabled or tweaked. This is for specialized 1137 environments which can tolerate a "non-standard" kernel. 1138 Only use this if you really know what you are doing. 1139 1140config HAVE_UID16 1141 bool 1142 1143config UID16 1144 bool "Enable 16-bit UID system calls" if EXPERT 1145 depends on HAVE_UID16 1146 default y 1147 help 1148 This enables the legacy 16-bit UID syscall wrappers. 1149 1150config SYSCTL_SYSCALL 1151 bool "Sysctl syscall support" if EXPERT 1152 depends on PROC_SYSCTL 1153 default n 1154 select SYSCTL 1155 ---help--- 1156 sys_sysctl uses binary paths that have been found challenging 1157 to properly maintain and use. The interface in /proc/sys 1158 using paths with ascii names is now the primary path to this 1159 information. 1160 1161 Almost nothing using the binary sysctl interface so if you are 1162 trying to save some space it is probably safe to disable this, 1163 making your kernel marginally smaller. 1164 1165 If unsure say N here. 1166 1167config SYSCTL_EXCEPTION_TRACE 1168 bool 1169 help 1170 Enable support for /proc/sys/debug/exception-trace. 1171 1172config KALLSYMS 1173 bool "Load all symbols for debugging/ksymoops" if EXPERT 1174 default y 1175 help 1176 Say Y here to let the kernel print out symbolic crash information and 1177 symbolic stack backtraces. This increases the size of the kernel 1178 somewhat, as all symbols have to be loaded into the kernel image. 1179 1180config KALLSYMS_ALL 1181 bool "Include all symbols in kallsyms" 1182 depends on DEBUG_KERNEL && KALLSYMS 1183 help 1184 Normally kallsyms only contains the symbols of functions for nicer 1185 OOPS messages and backtraces (i.e., symbols from the text and inittext 1186 sections). This is sufficient for most cases. And only in very rare 1187 cases (e.g., when a debugger is used) all symbols are required (e.g., 1188 names of variables from the data sections, etc). 1189 1190 This option makes sure that all symbols are loaded into the kernel 1191 image (i.e., symbols from all sections) in cost of increased kernel 1192 size (depending on the kernel configuration, it may be 300KiB or 1193 something like this). 1194 1195 Say N unless you really need all symbols. 1196 1197config HOTPLUG 1198 def_bool y 1199 1200config PRINTK 1201 default y 1202 bool "Enable support for printk" if EXPERT 1203 help 1204 This option enables normal printk support. Removing it 1205 eliminates most of the message strings from the kernel image 1206 and makes the kernel more or less silent. As this makes it 1207 very difficult to diagnose system problems, saying N here is 1208 strongly discouraged. 1209 1210config BUG 1211 bool "BUG() support" if EXPERT 1212 default y 1213 help 1214 Disabling this option eliminates support for BUG and WARN, reducing 1215 the size of your kernel image and potentially quietly ignoring 1216 numerous fatal conditions. You should only consider disabling this 1217 option for embedded systems with no facilities for reporting errors. 1218 Just say Y. 1219 1220config ELF_CORE 1221 depends on COREDUMP 1222 default y 1223 bool "Enable ELF core dumps" if EXPERT 1224 help 1225 Enable support for generating core dumps. Disabling saves about 4k. 1226 1227 1228config PCSPKR_PLATFORM 1229 bool "Enable PC-Speaker support" if EXPERT 1230 depends on HAVE_PCSPKR_PLATFORM 1231 select I8253_LOCK 1232 default y 1233 help 1234 This option allows to disable the internal PC-Speaker 1235 support, saving some memory. 1236 1237config HAVE_PCSPKR_PLATFORM 1238 bool 1239 1240config BASE_FULL 1241 default y 1242 bool "Enable full-sized data structures for core" if EXPERT 1243 help 1244 Disabling this option reduces the size of miscellaneous core 1245 kernel data structures. This saves memory on small machines, 1246 but may reduce performance. 1247 1248config FUTEX 1249 bool "Enable futex support" if EXPERT 1250 default y 1251 select RT_MUTEXES 1252 help 1253 Disabling this option will cause the kernel to be built without 1254 support for "fast userspace mutexes". The resulting kernel may not 1255 run glibc-based applications correctly. 1256 1257config EPOLL 1258 bool "Enable eventpoll support" if EXPERT 1259 default y 1260 select ANON_INODES 1261 help 1262 Disabling this option will cause the kernel to be built without 1263 support for epoll family of system calls. 1264 1265config SIGNALFD 1266 bool "Enable signalfd() system call" if EXPERT 1267 select ANON_INODES 1268 default y 1269 help 1270 Enable the signalfd() system call that allows to receive signals 1271 on a file descriptor. 1272 1273 If unsure, say Y. 1274 1275config TIMERFD 1276 bool "Enable timerfd() system call" if EXPERT 1277 select ANON_INODES 1278 default y 1279 help 1280 Enable the timerfd() system call that allows to receive timer 1281 events on a file descriptor. 1282 1283 If unsure, say Y. 1284 1285config EVENTFD 1286 bool "Enable eventfd() system call" if EXPERT 1287 select ANON_INODES 1288 default y 1289 help 1290 Enable the eventfd() system call that allows to receive both 1291 kernel notification (ie. KAIO) or userspace notifications. 1292 1293 If unsure, say Y. 1294 1295config SHMEM 1296 bool "Use full shmem filesystem" if EXPERT 1297 default y 1298 depends on MMU 1299 help 1300 The shmem is an internal filesystem used to manage shared memory. 1301 It is backed by swap and manages resource limits. It is also exported 1302 to userspace as tmpfs if TMPFS is enabled. Disabling this 1303 option replaces shmem and tmpfs with the much simpler ramfs code, 1304 which may be appropriate on small systems without swap. 1305 1306config AIO 1307 bool "Enable AIO support" if EXPERT 1308 default y 1309 help 1310 This option enables POSIX asynchronous I/O which may by used 1311 by some high performance threaded applications. Disabling 1312 this option saves about 7k. 1313 1314config EMBEDDED 1315 bool "Embedded system" 1316 select EXPERT 1317 help 1318 This option should be enabled if compiling the kernel for 1319 an embedded system so certain expert options are available 1320 for configuration. 1321 1322config HAVE_PERF_EVENTS 1323 bool 1324 help 1325 See tools/perf/design.txt for details. 1326 1327config PERF_USE_VMALLOC 1328 bool 1329 help 1330 See tools/perf/design.txt for details 1331 1332menu "Kernel Performance Events And Counters" 1333 1334config PERF_EVENTS 1335 bool "Kernel performance events and counters" 1336 default y if PROFILING 1337 depends on HAVE_PERF_EVENTS 1338 select ANON_INODES 1339 select IRQ_WORK 1340 help 1341 Enable kernel support for various performance events provided 1342 by software and hardware. 1343 1344 Software events are supported either built-in or via the 1345 use of generic tracepoints. 1346 1347 Most modern CPUs support performance events via performance 1348 counter registers. These registers count the number of certain 1349 types of hw events: such as instructions executed, cachemisses 1350 suffered, or branches mis-predicted - without slowing down the 1351 kernel or applications. These registers can also trigger interrupts 1352 when a threshold number of events have passed - and can thus be 1353 used to profile the code that runs on that CPU. 1354 1355 The Linux Performance Event subsystem provides an abstraction of 1356 these software and hardware event capabilities, available via a 1357 system call and used by the "perf" utility in tools/perf/. It 1358 provides per task and per CPU counters, and it provides event 1359 capabilities on top of those. 1360 1361 Say Y if unsure. 1362 1363config DEBUG_PERF_USE_VMALLOC 1364 default n 1365 bool "Debug: use vmalloc to back perf mmap() buffers" 1366 depends on PERF_EVENTS && DEBUG_KERNEL 1367 select PERF_USE_VMALLOC 1368 help 1369 Use vmalloc memory to back perf mmap() buffers. 1370 1371 Mostly useful for debugging the vmalloc code on platforms 1372 that don't require it. 1373 1374 Say N if unsure. 1375 1376endmenu 1377 1378config VM_EVENT_COUNTERS 1379 default y 1380 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1381 help 1382 VM event counters are needed for event counts to be shown. 1383 This option allows the disabling of the VM event counters 1384 on EXPERT systems. /proc/vmstat will only show page counts 1385 if VM event counters are disabled. 1386 1387config PCI_QUIRKS 1388 default y 1389 bool "Enable PCI quirk workarounds" if EXPERT 1390 depends on PCI 1391 help 1392 This enables workarounds for various PCI chipset 1393 bugs/quirks. Disable this only if your target machine is 1394 unaffected by PCI quirks. 1395 1396config SLUB_DEBUG 1397 default y 1398 bool "Enable SLUB debugging support" if EXPERT 1399 depends on SLUB && SYSFS 1400 help 1401 SLUB has extensive debug support features. Disabling these can 1402 result in significant savings in code size. This also disables 1403 SLUB sysfs support. /sys/slab will not exist and there will be 1404 no support for cache validation etc. 1405 1406config COMPAT_BRK 1407 bool "Disable heap randomization" 1408 default y 1409 help 1410 Randomizing heap placement makes heap exploits harder, but it 1411 also breaks ancient binaries (including anything libc5 based). 1412 This option changes the bootup default to heap randomization 1413 disabled, and can be overridden at runtime by setting 1414 /proc/sys/kernel/randomize_va_space to 2. 1415 1416 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1417 1418choice 1419 prompt "Choose SLAB allocator" 1420 default SLUB 1421 help 1422 This option allows to select a slab allocator. 1423 1424config SLAB 1425 bool "SLAB" 1426 help 1427 The regular slab allocator that is established and known to work 1428 well in all environments. It organizes cache hot objects in 1429 per cpu and per node queues. 1430 1431config SLUB 1432 bool "SLUB (Unqueued Allocator)" 1433 help 1434 SLUB is a slab allocator that minimizes cache line usage 1435 instead of managing queues of cached objects (SLAB approach). 1436 Per cpu caching is realized using slabs of objects instead 1437 of queues of objects. SLUB can use memory efficiently 1438 and has enhanced diagnostics. SLUB is the default choice for 1439 a slab allocator. 1440 1441config SLOB 1442 depends on EXPERT 1443 bool "SLOB (Simple Allocator)" 1444 help 1445 SLOB replaces the stock allocator with a drastically simpler 1446 allocator. SLOB is generally more space efficient but 1447 does not perform as well on large systems. 1448 1449endchoice 1450 1451config MMAP_ALLOW_UNINITIALIZED 1452 bool "Allow mmapped anonymous memory to be uninitialized" 1453 depends on EXPERT && !MMU 1454 default n 1455 help 1456 Normally, and according to the Linux spec, anonymous memory obtained 1457 from mmap() has it's contents cleared before it is passed to 1458 userspace. Enabling this config option allows you to request that 1459 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1460 providing a huge performance boost. If this option is not enabled, 1461 then the flag will be ignored. 1462 1463 This is taken advantage of by uClibc's malloc(), and also by 1464 ELF-FDPIC binfmt's brk and stack allocator. 1465 1466 Because of the obvious security issues, this option should only be 1467 enabled on embedded devices where you control what is run in 1468 userspace. Since that isn't generally a problem on no-MMU systems, 1469 it is normally safe to say Y here. 1470 1471 See Documentation/nommu-mmap.txt for more information. 1472 1473config PROFILING 1474 bool "Profiling support" 1475 help 1476 Say Y here to enable the extended profiling support mechanisms used 1477 by profilers such as OProfile. 1478 1479# 1480# Place an empty function call at each tracepoint site. Can be 1481# dynamically changed for a probe function. 1482# 1483config TRACEPOINTS 1484 bool 1485 1486source "arch/Kconfig" 1487 1488endmenu # General setup 1489 1490config HAVE_GENERIC_DMA_COHERENT 1491 bool 1492 default n 1493 1494config SLABINFO 1495 bool 1496 depends on PROC_FS 1497 depends on SLAB || SLUB_DEBUG 1498 default y 1499 1500config RT_MUTEXES 1501 boolean 1502 1503config BASE_SMALL 1504 int 1505 default 0 if BASE_FULL 1506 default 1 if !BASE_FULL 1507 1508menuconfig MODULES 1509 bool "Enable loadable module support" 1510 help 1511 Kernel modules are small pieces of compiled code which can 1512 be inserted in the running kernel, rather than being 1513 permanently built into the kernel. You use the "modprobe" 1514 tool to add (and sometimes remove) them. If you say Y here, 1515 many parts of the kernel can be built as modules (by 1516 answering M instead of Y where indicated): this is most 1517 useful for infrequently used options which are not required 1518 for booting. For more information, see the man pages for 1519 modprobe, lsmod, modinfo, insmod and rmmod. 1520 1521 If you say Y here, you will need to run "make 1522 modules_install" to put the modules under /lib/modules/ 1523 where modprobe can find them (you may need to be root to do 1524 this). 1525 1526 If unsure, say Y. 1527 1528if MODULES 1529 1530config MODULE_FORCE_LOAD 1531 bool "Forced module loading" 1532 default n 1533 help 1534 Allow loading of modules without version information (ie. modprobe 1535 --force). Forced module loading sets the 'F' (forced) taint flag and 1536 is usually a really bad idea. 1537 1538config MODULE_UNLOAD 1539 bool "Module unloading" 1540 help 1541 Without this option you will not be able to unload any 1542 modules (note that some modules may not be unloadable 1543 anyway), which makes your kernel smaller, faster 1544 and simpler. If unsure, say Y. 1545 1546config MODULE_FORCE_UNLOAD 1547 bool "Forced module unloading" 1548 depends on MODULE_UNLOAD && EXPERIMENTAL 1549 help 1550 This option allows you to force a module to unload, even if the 1551 kernel believes it is unsafe: the kernel will remove the module 1552 without waiting for anyone to stop using it (using the -f option to 1553 rmmod). This is mainly for kernel developers and desperate users. 1554 If unsure, say N. 1555 1556config MODVERSIONS 1557 bool "Module versioning support" 1558 help 1559 Usually, you have to use modules compiled with your kernel. 1560 Saying Y here makes it sometimes possible to use modules 1561 compiled for different kernels, by adding enough information 1562 to the modules to (hopefully) spot any changes which would 1563 make them incompatible with the kernel you are running. If 1564 unsure, say N. 1565 1566config MODULE_SRCVERSION_ALL 1567 bool "Source checksum for all modules" 1568 help 1569 Modules which contain a MODULE_VERSION get an extra "srcversion" 1570 field inserted into their modinfo section, which contains a 1571 sum of the source files which made it. This helps maintainers 1572 see exactly which source was used to build a module (since 1573 others sometimes change the module source without updating 1574 the version). With this option, such a "srcversion" field 1575 will be created for all modules. If unsure, say N. 1576 1577config MODULE_SIG 1578 bool "Module signature verification" 1579 depends on MODULES 1580 select KEYS 1581 select CRYPTO 1582 select ASYMMETRIC_KEY_TYPE 1583 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1584 select PUBLIC_KEY_ALGO_RSA 1585 select ASN1 1586 select OID_REGISTRY 1587 select X509_CERTIFICATE_PARSER 1588 help 1589 Check modules for valid signatures upon load: the signature 1590 is simply appended to the module. For more information see 1591 Documentation/module-signing.txt. 1592 1593 !!!WARNING!!! If you enable this option, you MUST make sure that the 1594 module DOES NOT get stripped after being signed. This includes the 1595 debuginfo strip done by some packagers (such as rpmbuild) and 1596 inclusion into an initramfs that wants the module size reduced. 1597 1598config MODULE_SIG_FORCE 1599 bool "Require modules to be validly signed" 1600 depends on MODULE_SIG 1601 help 1602 Reject unsigned modules or signed modules for which we don't have a 1603 key. Without this, such modules will simply taint the kernel. 1604 1605choice 1606 prompt "Which hash algorithm should modules be signed with?" 1607 depends on MODULE_SIG 1608 help 1609 This determines which sort of hashing algorithm will be used during 1610 signature generation. This algorithm _must_ be built into the kernel 1611 directly so that signature verification can take place. It is not 1612 possible to load a signed module containing the algorithm to check 1613 the signature on that module. 1614 1615config MODULE_SIG_SHA1 1616 bool "Sign modules with SHA-1" 1617 select CRYPTO_SHA1 1618 1619config MODULE_SIG_SHA224 1620 bool "Sign modules with SHA-224" 1621 select CRYPTO_SHA256 1622 1623config MODULE_SIG_SHA256 1624 bool "Sign modules with SHA-256" 1625 select CRYPTO_SHA256 1626 1627config MODULE_SIG_SHA384 1628 bool "Sign modules with SHA-384" 1629 select CRYPTO_SHA512 1630 1631config MODULE_SIG_SHA512 1632 bool "Sign modules with SHA-512" 1633 select CRYPTO_SHA512 1634 1635endchoice 1636 1637endif # MODULES 1638 1639config INIT_ALL_POSSIBLE 1640 bool 1641 help 1642 Back when each arch used to define their own cpu_online_mask and 1643 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1644 with all 1s, and others with all 0s. When they were centralised, 1645 it was better to provide this option than to break all the archs 1646 and have several arch maintainers pursuing me down dark alleys. 1647 1648config STOP_MACHINE 1649 bool 1650 default y 1651 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1652 help 1653 Need stop_machine() primitive. 1654 1655source "block/Kconfig" 1656 1657config PREEMPT_NOTIFIERS 1658 bool 1659 1660config PADATA 1661 depends on SMP 1662 bool 1663 1664# Can be selected by architectures with broken toolchains 1665# that get confused by correct const<->read_only section 1666# mappings 1667config BROKEN_RODATA 1668 bool 1669 1670config ASN1 1671 tristate 1672 help 1673 Build a simple ASN.1 grammar compiler that produces a bytecode output 1674 that can be interpreted by the ASN.1 stream decoder and used to 1675 inform it as to what tags are to be expected in a stream and what 1676 functions to call on what tags. 1677 1678source "kernel/Kconfig.locks" 1679