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 LOCALVERSION 57 string "Local version - append to kernel release" 58 help 59 Append an extra string to the end of your kernel version. 60 This will show up when you type uname, for example. 61 The string you set here will be appended after the contents of 62 any files with a filename matching localversion* in your 63 object and source tree, in that order. Your total string can 64 be a maximum of 64 characters. 65 66config LOCALVERSION_AUTO 67 bool "Automatically append version information to the version string" 68 default y 69 help 70 This will try to automatically determine if the current tree is a 71 release tree by looking for git tags that belong to the current 72 top of tree revision. 73 74 A string of the format -gxxxxxxxx will be added to the localversion 75 if a git-based tree is found. The string generated by this will be 76 appended after any matching localversion* files, and after the value 77 set in CONFIG_LOCALVERSION. 78 79 (The actual string used here is the first eight characters produced 80 by running the command: 81 82 $ git rev-parse --verify HEAD 83 84 which is done within the script "scripts/setlocalversion".) 85 86config HAVE_KERNEL_GZIP 87 bool 88 89config HAVE_KERNEL_BZIP2 90 bool 91 92config HAVE_KERNEL_LZMA 93 bool 94 95config HAVE_KERNEL_XZ 96 bool 97 98config HAVE_KERNEL_LZO 99 bool 100 101choice 102 prompt "Kernel compression mode" 103 default KERNEL_GZIP 104 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO 105 help 106 The linux kernel is a kind of self-extracting executable. 107 Several compression algorithms are available, which differ 108 in efficiency, compression and decompression speed. 109 Compression speed is only relevant when building a kernel. 110 Decompression speed is relevant at each boot. 111 112 If you have any problems with bzip2 or lzma compressed 113 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 114 version of this functionality (bzip2 only), for 2.4, was 115 supplied by Christian Ludwig) 116 117 High compression options are mostly useful for users, who 118 are low on disk space (embedded systems), but for whom ram 119 size matters less. 120 121 If in doubt, select 'gzip' 122 123config KERNEL_GZIP 124 bool "Gzip" 125 depends on HAVE_KERNEL_GZIP 126 help 127 The old and tried gzip compression. It provides a good balance 128 between compression ratio and decompression speed. 129 130config KERNEL_BZIP2 131 bool "Bzip2" 132 depends on HAVE_KERNEL_BZIP2 133 help 134 Its compression ratio and speed is intermediate. 135 Decompression speed is slowest among the choices. The kernel 136 size is about 10% smaller with bzip2, in comparison to gzip. 137 Bzip2 uses a large amount of memory. For modern kernels you 138 will need at least 8MB RAM or more for booting. 139 140config KERNEL_LZMA 141 bool "LZMA" 142 depends on HAVE_KERNEL_LZMA 143 help 144 This compression algorithm's ratio is best. Decompression speed 145 is between gzip and bzip2. Compression is slowest. 146 The kernel size is about 33% smaller with LZMA in comparison to gzip. 147 148config KERNEL_XZ 149 bool "XZ" 150 depends on HAVE_KERNEL_XZ 151 help 152 XZ uses the LZMA2 algorithm and instruction set specific 153 BCJ filters which can improve compression ratio of executable 154 code. The size of the kernel is about 30% smaller with XZ in 155 comparison to gzip. On architectures for which there is a BCJ 156 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 157 will create a few percent smaller kernel than plain LZMA. 158 159 The speed is about the same as with LZMA: The decompression 160 speed of XZ is better than that of bzip2 but worse than gzip 161 and LZO. Compression is slow. 162 163config KERNEL_LZO 164 bool "LZO" 165 depends on HAVE_KERNEL_LZO 166 help 167 Its compression ratio is the poorest among the choices. The kernel 168 size is about 10% bigger than gzip; however its speed 169 (both compression and decompression) is the fastest. 170 171endchoice 172 173config DEFAULT_HOSTNAME 174 string "Default hostname" 175 default "(none)" 176 help 177 This option determines the default system hostname before userspace 178 calls sethostname(2). The kernel traditionally uses "(none)" here, 179 but you may wish to use a different default here to make a minimal 180 system more usable with less configuration. 181 182config SWAP 183 bool "Support for paging of anonymous memory (swap)" 184 depends on MMU && BLOCK 185 default y 186 help 187 This option allows you to choose whether you want to have support 188 for so called swap devices or swap files in your kernel that are 189 used to provide more virtual memory than the actual RAM present 190 in your computer. If unsure say Y. 191 192config SYSVIPC 193 bool "System V IPC" 194 ---help--- 195 Inter Process Communication is a suite of library functions and 196 system calls which let processes (running programs) synchronize and 197 exchange information. It is generally considered to be a good thing, 198 and some programs won't run unless you say Y here. In particular, if 199 you want to run the DOS emulator dosemu under Linux (read the 200 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 201 you'll need to say Y here. 202 203 You can find documentation about IPC with "info ipc" and also in 204 section 6.4 of the Linux Programmer's Guide, available from 205 <http://www.tldp.org/guides.html>. 206 207config SYSVIPC_SYSCTL 208 bool 209 depends on SYSVIPC 210 depends on SYSCTL 211 default y 212 213config POSIX_MQUEUE 214 bool "POSIX Message Queues" 215 depends on NET 216 ---help--- 217 POSIX variant of message queues is a part of IPC. In POSIX message 218 queues every message has a priority which decides about succession 219 of receiving it by a process. If you want to compile and run 220 programs written e.g. for Solaris with use of its POSIX message 221 queues (functions mq_*) say Y here. 222 223 POSIX message queues are visible as a filesystem called 'mqueue' 224 and can be mounted somewhere if you want to do filesystem 225 operations on message queues. 226 227 If unsure, say Y. 228 229config POSIX_MQUEUE_SYSCTL 230 bool 231 depends on POSIX_MQUEUE 232 depends on SYSCTL 233 default y 234 235config FHANDLE 236 bool "open by fhandle syscalls" 237 select EXPORTFS 238 help 239 If you say Y here, a user level program will be able to map 240 file names to handle and then later use the handle for 241 different file system operations. This is useful in implementing 242 userspace file servers, which now track files using handles instead 243 of names. The handle would remain the same even if file names 244 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 245 syscalls. 246 247config AUDIT 248 bool "Auditing support" 249 depends on NET 250 help 251 Enable auditing infrastructure that can be used with another 252 kernel subsystem, such as SELinux (which requires this for 253 logging of avc messages output). Does not do system-call 254 auditing without CONFIG_AUDITSYSCALL. 255 256config AUDITSYSCALL 257 bool "Enable system-call auditing support" 258 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT)) 259 default y if SECURITY_SELINUX 260 help 261 Enable low-overhead system-call auditing infrastructure that 262 can be used independently or with another kernel subsystem, 263 such as SELinux. 264 265config AUDIT_WATCH 266 def_bool y 267 depends on AUDITSYSCALL 268 select FSNOTIFY 269 270config AUDIT_TREE 271 def_bool y 272 depends on AUDITSYSCALL 273 select FSNOTIFY 274 275config AUDIT_LOGINUID_IMMUTABLE 276 bool "Make audit loginuid immutable" 277 depends on AUDIT 278 help 279 The config option toggles if a task setting its loginuid requires 280 CAP_SYS_AUDITCONTROL or if that task should require no special permissions 281 but should instead only allow setting its loginuid if it was never 282 previously set. On systems which use systemd or a similar central 283 process to restart login services this should be set to true. On older 284 systems in which an admin would typically have to directly stop and 285 start processes this should be set to false. Setting this to true allows 286 one to drop potentially dangerous capabilites from the login tasks, 287 but may not be backwards compatible with older init systems. 288 289source "kernel/irq/Kconfig" 290source "kernel/time/Kconfig" 291 292menu "CPU/Task time and stats accounting" 293 294config VIRT_CPU_ACCOUNTING 295 bool 296 297choice 298 prompt "Cputime accounting" 299 default TICK_CPU_ACCOUNTING if !PPC64 300 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 301 302# Kind of a stub config for the pure tick based cputime accounting 303config TICK_CPU_ACCOUNTING 304 bool "Simple tick based cputime accounting" 305 depends on !S390 && !NO_HZ_FULL 306 help 307 This is the basic tick based cputime accounting that maintains 308 statistics about user, system and idle time spent on per jiffies 309 granularity. 310 311 If unsure, say Y. 312 313config VIRT_CPU_ACCOUNTING_NATIVE 314 bool "Deterministic task and CPU time accounting" 315 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 316 select VIRT_CPU_ACCOUNTING 317 help 318 Select this option to enable more accurate task and CPU time 319 accounting. This is done by reading a CPU counter on each 320 kernel entry and exit and on transitions within the kernel 321 between system, softirq and hardirq state, so there is a 322 small performance impact. In the case of s390 or IBM POWER > 5, 323 this also enables accounting of stolen time on logically-partitioned 324 systems. 325 326config VIRT_CPU_ACCOUNTING_GEN 327 bool "Full dynticks CPU time accounting" 328 depends on HAVE_CONTEXT_TRACKING && 64BIT 329 select VIRT_CPU_ACCOUNTING 330 select CONTEXT_TRACKING 331 help 332 Select this option to enable task and CPU time accounting on full 333 dynticks systems. This accounting is implemented by watching every 334 kernel-user boundaries using the context tracking subsystem. 335 The accounting is thus performed at the expense of some significant 336 overhead. 337 338 For now this is only useful if you are working on the full 339 dynticks subsystem development. 340 341 If unsure, say N. 342 343config IRQ_TIME_ACCOUNTING 344 bool "Fine granularity task level IRQ time accounting" 345 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL 346 help 347 Select this option to enable fine granularity task irq time 348 accounting. This is done by reading a timestamp on each 349 transitions between softirq and hardirq state, so there can be a 350 small performance impact. 351 352 If in doubt, say N here. 353 354endchoice 355 356config BSD_PROCESS_ACCT 357 bool "BSD Process Accounting" 358 help 359 If you say Y here, a user level program will be able to instruct the 360 kernel (via a special system call) to write process accounting 361 information to a file: whenever a process exits, information about 362 that process will be appended to the file by the kernel. The 363 information includes things such as creation time, owning user, 364 command name, memory usage, controlling terminal etc. (the complete 365 list is in the struct acct in <file:include/linux/acct.h>). It is 366 up to the user level program to do useful things with this 367 information. This is generally a good idea, so say Y. 368 369config BSD_PROCESS_ACCT_V3 370 bool "BSD Process Accounting version 3 file format" 371 depends on BSD_PROCESS_ACCT 372 default n 373 help 374 If you say Y here, the process accounting information is written 375 in a new file format that also logs the process IDs of each 376 process and it's parent. Note that this file format is incompatible 377 with previous v0/v1/v2 file formats, so you will need updated tools 378 for processing it. A preliminary version of these tools is available 379 at <http://www.gnu.org/software/acct/>. 380 381config TASKSTATS 382 bool "Export task/process statistics through netlink" 383 depends on NET 384 default n 385 help 386 Export selected statistics for tasks/processes through the 387 generic netlink interface. Unlike BSD process accounting, the 388 statistics are available during the lifetime of tasks/processes as 389 responses to commands. Like BSD accounting, they are sent to user 390 space on task exit. 391 392 Say N if unsure. 393 394config TASK_DELAY_ACCT 395 bool "Enable per-task delay accounting" 396 depends on TASKSTATS 397 help 398 Collect information on time spent by a task waiting for system 399 resources like cpu, synchronous block I/O completion and swapping 400 in pages. Such statistics can help in setting a task's priorities 401 relative to other tasks for cpu, io, rss limits etc. 402 403 Say N if unsure. 404 405config TASK_XACCT 406 bool "Enable extended accounting over taskstats" 407 depends on TASKSTATS 408 help 409 Collect extended task accounting data and send the data 410 to userland for processing over the taskstats interface. 411 412 Say N if unsure. 413 414config TASK_IO_ACCOUNTING 415 bool "Enable per-task storage I/O accounting" 416 depends on TASK_XACCT 417 help 418 Collect information on the number of bytes of storage I/O which this 419 task has caused. 420 421 Say N if unsure. 422 423endmenu # "CPU/Task time and stats accounting" 424 425menu "RCU Subsystem" 426 427choice 428 prompt "RCU Implementation" 429 default TREE_RCU 430 431config TREE_RCU 432 bool "Tree-based hierarchical RCU" 433 depends on !PREEMPT && SMP 434 select IRQ_WORK 435 help 436 This option selects the RCU implementation that is 437 designed for very large SMP system with hundreds or 438 thousands of CPUs. It also scales down nicely to 439 smaller systems. 440 441config TREE_PREEMPT_RCU 442 bool "Preemptible tree-based hierarchical RCU" 443 depends on PREEMPT 444 help 445 This option selects the RCU implementation that is 446 designed for very large SMP systems with hundreds or 447 thousands of CPUs, but for which real-time response 448 is also required. It also scales down nicely to 449 smaller systems. 450 451 Select this option if you are unsure. 452 453config TINY_RCU 454 bool "UP-only small-memory-footprint RCU" 455 depends on !PREEMPT && !SMP 456 help 457 This option selects the RCU implementation that is 458 designed for UP systems from which real-time response 459 is not required. This option greatly reduces the 460 memory footprint of RCU. 461 462config TINY_PREEMPT_RCU 463 bool "Preemptible UP-only small-memory-footprint RCU" 464 depends on PREEMPT && !SMP 465 help 466 This option selects the RCU implementation that is designed 467 for real-time UP systems. This option greatly reduces the 468 memory footprint of RCU. 469 470endchoice 471 472config PREEMPT_RCU 473 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU ) 474 help 475 This option enables preemptible-RCU code that is common between 476 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 477 478config RCU_STALL_COMMON 479 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE ) 480 help 481 This option enables RCU CPU stall code that is common between 482 the TINY and TREE variants of RCU. The purpose is to allow 483 the tiny variants to disable RCU CPU stall warnings, while 484 making these warnings mandatory for the tree variants. 485 486config CONTEXT_TRACKING 487 bool 488 489config RCU_USER_QS 490 bool "Consider userspace as in RCU extended quiescent state" 491 depends on HAVE_CONTEXT_TRACKING && SMP 492 select CONTEXT_TRACKING 493 help 494 This option sets hooks on kernel / userspace boundaries and 495 puts RCU in extended quiescent state when the CPU runs in 496 userspace. It means that when a CPU runs in userspace, it is 497 excluded from the global RCU state machine and thus doesn't 498 try to keep the timer tick on for RCU. 499 500 Unless you want to hack and help the development of the full 501 dynticks mode, you shouldn't enable this option. It also 502 adds unnecessary overhead. 503 504 If unsure say N 505 506config CONTEXT_TRACKING_FORCE 507 bool "Force context tracking" 508 depends on CONTEXT_TRACKING 509 default CONTEXT_TRACKING 510 help 511 Probe on user/kernel boundaries by default in order to 512 test the features that rely on it such as userspace RCU extended 513 quiescent states. 514 This test is there for debugging until we have a real user like the 515 full dynticks mode. 516 517config RCU_FANOUT 518 int "Tree-based hierarchical RCU fanout value" 519 range 2 64 if 64BIT 520 range 2 32 if !64BIT 521 depends on TREE_RCU || TREE_PREEMPT_RCU 522 default 64 if 64BIT 523 default 32 if !64BIT 524 help 525 This option controls the fanout of hierarchical implementations 526 of RCU, allowing RCU to work efficiently on machines with 527 large numbers of CPUs. This value must be at least the fourth 528 root of NR_CPUS, which allows NR_CPUS to be insanely large. 529 The default value of RCU_FANOUT should be used for production 530 systems, but if you are stress-testing the RCU implementation 531 itself, small RCU_FANOUT values allow you to test large-system 532 code paths on small(er) systems. 533 534 Select a specific number if testing RCU itself. 535 Take the default if unsure. 536 537config RCU_FANOUT_LEAF 538 int "Tree-based hierarchical RCU leaf-level fanout value" 539 range 2 RCU_FANOUT if 64BIT 540 range 2 RCU_FANOUT if !64BIT 541 depends on TREE_RCU || TREE_PREEMPT_RCU 542 default 16 543 help 544 This option controls the leaf-level fanout of hierarchical 545 implementations of RCU, and allows trading off cache misses 546 against lock contention. Systems that synchronize their 547 scheduling-clock interrupts for energy-efficiency reasons will 548 want the default because the smaller leaf-level fanout keeps 549 lock contention levels acceptably low. Very large systems 550 (hundreds or thousands of CPUs) will instead want to set this 551 value to the maximum value possible in order to reduce the 552 number of cache misses incurred during RCU's grace-period 553 initialization. These systems tend to run CPU-bound, and thus 554 are not helped by synchronized interrupts, and thus tend to 555 skew them, which reduces lock contention enough that large 556 leaf-level fanouts work well. 557 558 Select a specific number if testing RCU itself. 559 560 Select the maximum permissible value for large systems. 561 562 Take the default if unsure. 563 564config RCU_FANOUT_EXACT 565 bool "Disable tree-based hierarchical RCU auto-balancing" 566 depends on TREE_RCU || TREE_PREEMPT_RCU 567 default n 568 help 569 This option forces use of the exact RCU_FANOUT value specified, 570 regardless of imbalances in the hierarchy. This is useful for 571 testing RCU itself, and might one day be useful on systems with 572 strong NUMA behavior. 573 574 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 575 576 Say N if unsure. 577 578config RCU_FAST_NO_HZ 579 bool "Accelerate last non-dyntick-idle CPU's grace periods" 580 depends on NO_HZ_COMMON && SMP 581 default n 582 help 583 This option permits CPUs to enter dynticks-idle state even if 584 they have RCU callbacks queued, and prevents RCU from waking 585 these CPUs up more than roughly once every four jiffies (by 586 default, you can adjust this using the rcutree.rcu_idle_gp_delay 587 parameter), thus improving energy efficiency. On the other 588 hand, this option increases the duration of RCU grace periods, 589 for example, slowing down synchronize_rcu(). 590 591 Say Y if energy efficiency is critically important, and you 592 don't care about increased grace-period durations. 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 658config RCU_NOCB_CPU 659 bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL" 660 depends on TREE_RCU || TREE_PREEMPT_RCU 661 default n 662 help 663 Use this option to reduce OS jitter for aggressive HPC or 664 real-time workloads. It can also be used to offload RCU 665 callback invocation to energy-efficient CPUs in battery-powered 666 asymmetric multiprocessors. 667 668 This option offloads callback invocation from the set of 669 CPUs specified at boot time by the rcu_nocbs parameter. 670 For each such CPU, a kthread ("rcuox/N") will be created to 671 invoke callbacks, where the "N" is the CPU being offloaded, 672 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 673 "s" for RCU-sched. Nothing prevents this kthread from running 674 on the specified CPUs, but (1) the kthreads may be preempted 675 between each callback, and (2) affinity or cgroups can be used 676 to force the kthreads to run on whatever set of CPUs is desired. 677 678 Say Y here if you want to help to debug reduced OS jitter. 679 Say N here if you are unsure. 680 681choice 682 prompt "Build-forced no-CBs CPUs" 683 default RCU_NOCB_CPU_NONE 684 help 685 This option allows no-CBs CPUs to be specified at build time. 686 Additional no-CBs CPUs may be specified by the rcu_nocbs= 687 boot parameter. 688 689config RCU_NOCB_CPU_NONE 690 bool "No build_forced no-CBs CPUs" 691 depends on RCU_NOCB_CPU && !NO_HZ_FULL 692 help 693 This option does not force any of the CPUs to be no-CBs CPUs. 694 Only CPUs designated by the rcu_nocbs= boot parameter will be 695 no-CBs CPUs. 696 697config RCU_NOCB_CPU_ZERO 698 bool "CPU 0 is a build_forced no-CBs CPU" 699 depends on RCU_NOCB_CPU && !NO_HZ_FULL 700 help 701 This option forces CPU 0 to be a no-CBs CPU. Additional CPUs 702 may be designated as no-CBs CPUs using the rcu_nocbs= boot 703 parameter will be no-CBs CPUs. 704 705 Select this if CPU 0 needs to be a no-CBs CPU for real-time 706 or energy-efficiency reasons. 707 708config RCU_NOCB_CPU_ALL 709 bool "All CPUs are build_forced no-CBs CPUs" 710 depends on RCU_NOCB_CPU 711 help 712 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 713 boot parameter will be ignored. 714 715 Select this if all CPUs need to be no-CBs CPUs for real-time 716 or energy-efficiency reasons. 717 718endchoice 719 720endmenu # "RCU Subsystem" 721 722config IKCONFIG 723 tristate "Kernel .config support" 724 ---help--- 725 This option enables the complete Linux kernel ".config" file 726 contents to be saved in the kernel. It provides documentation 727 of which kernel options are used in a running kernel or in an 728 on-disk kernel. This information can be extracted from the kernel 729 image file with the script scripts/extract-ikconfig and used as 730 input to rebuild the current kernel or to build another kernel. 731 It can also be extracted from a running kernel by reading 732 /proc/config.gz if enabled (below). 733 734config IKCONFIG_PROC 735 bool "Enable access to .config through /proc/config.gz" 736 depends on IKCONFIG && PROC_FS 737 ---help--- 738 This option enables access to the kernel configuration file 739 through /proc/config.gz. 740 741config LOG_BUF_SHIFT 742 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 743 range 12 21 744 default 17 745 help 746 Select kernel log buffer size as a power of 2. 747 Examples: 748 17 => 128 KB 749 16 => 64 KB 750 15 => 32 KB 751 14 => 16 KB 752 13 => 8 KB 753 12 => 4 KB 754 755# 756# Architectures with an unreliable sched_clock() should select this: 757# 758config HAVE_UNSTABLE_SCHED_CLOCK 759 bool 760 761# 762# For architectures that want to enable the support for NUMA-affine scheduler 763# balancing logic: 764# 765config ARCH_SUPPORTS_NUMA_BALANCING 766 bool 767 768# For architectures that (ab)use NUMA to represent different memory regions 769# all cpu-local but of different latencies, such as SuperH. 770# 771config ARCH_WANT_NUMA_VARIABLE_LOCALITY 772 bool 773 774# 775# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE 776config ARCH_WANTS_PROT_NUMA_PROT_NONE 777 bool 778 779config ARCH_USES_NUMA_PROT_NONE 780 bool 781 default y 782 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE 783 depends on NUMA_BALANCING 784 785config NUMA_BALANCING_DEFAULT_ENABLED 786 bool "Automatically enable NUMA aware memory/task placement" 787 default y 788 depends on NUMA_BALANCING 789 help 790 If set, autonumic NUMA balancing will be enabled if running on a NUMA 791 machine. 792 793config NUMA_BALANCING 794 bool "Memory placement aware NUMA scheduler" 795 depends on ARCH_SUPPORTS_NUMA_BALANCING 796 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 797 depends on SMP && NUMA && MIGRATION 798 help 799 This option adds support for automatic NUMA aware memory/task placement. 800 The mechanism is quite primitive and is based on migrating memory when 801 it is references to the node the task is running on. 802 803 This system will be inactive on UMA systems. 804 805menuconfig CGROUPS 806 boolean "Control Group support" 807 depends on EVENTFD 808 help 809 This option adds support for grouping sets of processes together, for 810 use with process control subsystems such as Cpusets, CFS, memory 811 controls or device isolation. 812 See 813 - Documentation/scheduler/sched-design-CFS.txt (CFS) 814 - Documentation/cgroups/ (features for grouping, isolation 815 and resource control) 816 817 Say N if unsure. 818 819if CGROUPS 820 821config CGROUP_DEBUG 822 bool "Example debug cgroup subsystem" 823 default n 824 help 825 This option enables a simple cgroup subsystem that 826 exports useful debugging information about the cgroups 827 framework. 828 829 Say N if unsure. 830 831config CGROUP_FREEZER 832 bool "Freezer cgroup subsystem" 833 help 834 Provides a way to freeze and unfreeze all tasks in a 835 cgroup. 836 837config CGROUP_DEVICE 838 bool "Device controller for cgroups" 839 help 840 Provides a cgroup implementing whitelists for devices which 841 a process in the cgroup can mknod or open. 842 843config CPUSETS 844 bool "Cpuset support" 845 help 846 This option will let you create and manage CPUSETs which 847 allow dynamically partitioning a system into sets of CPUs and 848 Memory Nodes and assigning tasks to run only within those sets. 849 This is primarily useful on large SMP or NUMA systems. 850 851 Say N if unsure. 852 853config PROC_PID_CPUSET 854 bool "Include legacy /proc/<pid>/cpuset file" 855 depends on CPUSETS 856 default y 857 858config CGROUP_CPUACCT 859 bool "Simple CPU accounting cgroup subsystem" 860 help 861 Provides a simple Resource Controller for monitoring the 862 total CPU consumed by the tasks in a cgroup. 863 864config RESOURCE_COUNTERS 865 bool "Resource counters" 866 help 867 This option enables controller independent resource accounting 868 infrastructure that works with cgroups. 869 870config MEMCG 871 bool "Memory Resource Controller for Control Groups" 872 depends on RESOURCE_COUNTERS 873 select MM_OWNER 874 help 875 Provides a memory resource controller that manages both anonymous 876 memory and page cache. (See Documentation/cgroups/memory.txt) 877 878 Note that setting this option increases fixed memory overhead 879 associated with each page of memory in the system. By this, 880 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 881 usage tracking struct at boot. Total amount of this is printed out 882 at boot. 883 884 Only enable when you're ok with these trade offs and really 885 sure you need the memory resource controller. Even when you enable 886 this, you can set "cgroup_disable=memory" at your boot option to 887 disable memory resource controller and you can avoid overheads. 888 (and lose benefits of memory resource controller) 889 890 This config option also selects MM_OWNER config option, which 891 could in turn add some fork/exit overhead. 892 893config MEMCG_SWAP 894 bool "Memory Resource Controller Swap Extension" 895 depends on MEMCG && SWAP 896 help 897 Add swap management feature to memory resource controller. When you 898 enable this, you can limit mem+swap usage per cgroup. In other words, 899 when you disable this, memory resource controller has no cares to 900 usage of swap...a process can exhaust all of the swap. This extension 901 is useful when you want to avoid exhaustion swap but this itself 902 adds more overheads and consumes memory for remembering information. 903 Especially if you use 32bit system or small memory system, please 904 be careful about enabling this. When memory resource controller 905 is disabled by boot option, this will be automatically disabled and 906 there will be no overhead from this. Even when you set this config=y, 907 if boot option "swapaccount=0" is set, swap will not be accounted. 908 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 909 size is 4096bytes, 512k per 1Gbytes of swap. 910config MEMCG_SWAP_ENABLED 911 bool "Memory Resource Controller Swap Extension enabled by default" 912 depends on MEMCG_SWAP 913 default y 914 help 915 Memory Resource Controller Swap Extension comes with its price in 916 a bigger memory consumption. General purpose distribution kernels 917 which want to enable the feature but keep it disabled by default 918 and let the user enable it by swapaccount boot command line 919 parameter should have this option unselected. 920 For those who want to have the feature enabled by default should 921 select this option (if, for some reason, they need to disable it 922 then swapaccount=0 does the trick). 923config MEMCG_KMEM 924 bool "Memory Resource Controller Kernel Memory accounting" 925 depends on MEMCG 926 depends on SLUB || SLAB 927 help 928 The Kernel Memory extension for Memory Resource Controller can limit 929 the amount of memory used by kernel objects in the system. Those are 930 fundamentally different from the entities handled by the standard 931 Memory Controller, which are page-based, and can be swapped. Users of 932 the kmem extension can use it to guarantee that no group of processes 933 will ever exhaust kernel resources alone. 934 935config CGROUP_HUGETLB 936 bool "HugeTLB Resource Controller for Control Groups" 937 depends on RESOURCE_COUNTERS && HUGETLB_PAGE 938 default n 939 help 940 Provides a cgroup Resource Controller for HugeTLB pages. 941 When you enable this, you can put a per cgroup limit on HugeTLB usage. 942 The limit is enforced during page fault. Since HugeTLB doesn't 943 support page reclaim, enforcing the limit at page fault time implies 944 that, the application will get SIGBUS signal if it tries to access 945 HugeTLB pages beyond its limit. This requires the application to know 946 beforehand how much HugeTLB pages it would require for its use. The 947 control group is tracked in the third page lru pointer. This means 948 that we cannot use the controller with huge page less than 3 pages. 949 950config CGROUP_PERF 951 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 952 depends on PERF_EVENTS && CGROUPS 953 help 954 This option extends the per-cpu mode to restrict monitoring to 955 threads which belong to the cgroup specified and run on the 956 designated cpu. 957 958 Say N if unsure. 959 960menuconfig CGROUP_SCHED 961 bool "Group CPU scheduler" 962 default n 963 help 964 This feature lets CPU scheduler recognize task groups and control CPU 965 bandwidth allocation to such task groups. It uses cgroups to group 966 tasks. 967 968if CGROUP_SCHED 969config FAIR_GROUP_SCHED 970 bool "Group scheduling for SCHED_OTHER" 971 depends on CGROUP_SCHED 972 default CGROUP_SCHED 973 974config CFS_BANDWIDTH 975 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 976 depends on FAIR_GROUP_SCHED 977 default n 978 help 979 This option allows users to define CPU bandwidth rates (limits) for 980 tasks running within the fair group scheduler. Groups with no limit 981 set are considered to be unconstrained and will run with no 982 restriction. 983 See tip/Documentation/scheduler/sched-bwc.txt for more information. 984 985config RT_GROUP_SCHED 986 bool "Group scheduling for SCHED_RR/FIFO" 987 depends on CGROUP_SCHED 988 default n 989 help 990 This feature lets you explicitly allocate real CPU bandwidth 991 to task groups. If enabled, it will also make it impossible to 992 schedule realtime tasks for non-root users until you allocate 993 realtime bandwidth for them. 994 See Documentation/scheduler/sched-rt-group.txt for more information. 995 996endif #CGROUP_SCHED 997 998config BLK_CGROUP 999 bool "Block IO controller" 1000 depends on BLOCK 1001 default n 1002 ---help--- 1003 Generic block IO controller cgroup interface. This is the common 1004 cgroup interface which should be used by various IO controlling 1005 policies. 1006 1007 Currently, CFQ IO scheduler uses it to recognize task groups and 1008 control disk bandwidth allocation (proportional time slice allocation) 1009 to such task groups. It is also used by bio throttling logic in 1010 block layer to implement upper limit in IO rates on a device. 1011 1012 This option only enables generic Block IO controller infrastructure. 1013 One needs to also enable actual IO controlling logic/policy. For 1014 enabling proportional weight division of disk bandwidth in CFQ, set 1015 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1016 CONFIG_BLK_DEV_THROTTLING=y. 1017 1018 See Documentation/cgroups/blkio-controller.txt for more information. 1019 1020config DEBUG_BLK_CGROUP 1021 bool "Enable Block IO controller debugging" 1022 depends on BLK_CGROUP 1023 default n 1024 ---help--- 1025 Enable some debugging help. Currently it exports additional stat 1026 files in a cgroup which can be useful for debugging. 1027 1028endif # CGROUPS 1029 1030config CHECKPOINT_RESTORE 1031 bool "Checkpoint/restore support" if EXPERT 1032 default n 1033 help 1034 Enables additional kernel features in a sake of checkpoint/restore. 1035 In particular it adds auxiliary prctl codes to setup process text, 1036 data and heap segment sizes, and a few additional /proc filesystem 1037 entries. 1038 1039 If unsure, say N here. 1040 1041menuconfig NAMESPACES 1042 bool "Namespaces support" if EXPERT 1043 default !EXPERT 1044 help 1045 Provides the way to make tasks work with different objects using 1046 the same id. For example same IPC id may refer to different objects 1047 or same user id or pid may refer to different tasks when used in 1048 different namespaces. 1049 1050if NAMESPACES 1051 1052config UTS_NS 1053 bool "UTS namespace" 1054 default y 1055 help 1056 In this namespace tasks see different info provided with the 1057 uname() system call 1058 1059config IPC_NS 1060 bool "IPC namespace" 1061 depends on (SYSVIPC || POSIX_MQUEUE) 1062 default y 1063 help 1064 In this namespace tasks work with IPC ids which correspond to 1065 different IPC objects in different namespaces. 1066 1067config USER_NS 1068 bool "User namespace" 1069 depends on UIDGID_CONVERTED 1070 select UIDGID_STRICT_TYPE_CHECKS 1071 1072 default n 1073 help 1074 This allows containers, i.e. vservers, to use user namespaces 1075 to provide different user info for different servers. 1076 1077 When user namespaces are enabled in the kernel it is 1078 recommended that the MEMCG and MEMCG_KMEM options also be 1079 enabled and that user-space use the memory control groups to 1080 limit the amount of memory a memory unprivileged users can 1081 use. 1082 1083 If unsure, say N. 1084 1085config PID_NS 1086 bool "PID Namespaces" 1087 default y 1088 help 1089 Support process id namespaces. This allows having multiple 1090 processes with the same pid as long as they are in different 1091 pid namespaces. This is a building block of containers. 1092 1093config NET_NS 1094 bool "Network namespace" 1095 depends on NET 1096 default y 1097 help 1098 Allow user space to create what appear to be multiple instances 1099 of the network stack. 1100 1101endif # NAMESPACES 1102 1103config UIDGID_CONVERTED 1104 # True if all of the selected software conmponents are known 1105 # to have uid_t and gid_t converted to kuid_t and kgid_t 1106 # where appropriate and are otherwise safe to use with 1107 # the user namespace. 1108 bool 1109 default y 1110 1111 # Filesystems 1112 depends on XFS_FS = n 1113 1114config UIDGID_STRICT_TYPE_CHECKS 1115 bool "Require conversions between uid/gids and their internal representation" 1116 depends on UIDGID_CONVERTED 1117 default n 1118 help 1119 While the nececessary conversions are being added to all subsystems this option allows 1120 the code to continue to build for unconverted subsystems. 1121 1122 Say Y here if you want the strict type checking enabled 1123 1124config SCHED_AUTOGROUP 1125 bool "Automatic process group scheduling" 1126 select EVENTFD 1127 select CGROUPS 1128 select CGROUP_SCHED 1129 select FAIR_GROUP_SCHED 1130 help 1131 This option optimizes the scheduler for common desktop workloads by 1132 automatically creating and populating task groups. This separation 1133 of workloads isolates aggressive CPU burners (like build jobs) from 1134 desktop applications. Task group autogeneration is currently based 1135 upon task session. 1136 1137config MM_OWNER 1138 bool 1139 1140config SYSFS_DEPRECATED 1141 bool "Enable deprecated sysfs features to support old userspace tools" 1142 depends on SYSFS 1143 default n 1144 help 1145 This option adds code that switches the layout of the "block" class 1146 devices, to not show up in /sys/class/block/, but only in 1147 /sys/block/. 1148 1149 This switch is only active when the sysfs.deprecated=1 boot option is 1150 passed or the SYSFS_DEPRECATED_V2 option is set. 1151 1152 This option allows new kernels to run on old distributions and tools, 1153 which might get confused by /sys/class/block/. Since 2007/2008 all 1154 major distributions and tools handle this just fine. 1155 1156 Recent distributions and userspace tools after 2009/2010 depend on 1157 the existence of /sys/class/block/, and will not work with this 1158 option enabled. 1159 1160 Only if you are using a new kernel on an old distribution, you might 1161 need to say Y here. 1162 1163config SYSFS_DEPRECATED_V2 1164 bool "Enable deprecated sysfs features by default" 1165 default n 1166 depends on SYSFS 1167 depends on SYSFS_DEPRECATED 1168 help 1169 Enable deprecated sysfs by default. 1170 1171 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1172 option. 1173 1174 Only if you are using a new kernel on an old distribution, you might 1175 need to say Y here. Even then, odds are you would not need it 1176 enabled, you can always pass the boot option if absolutely necessary. 1177 1178config RELAY 1179 bool "Kernel->user space relay support (formerly relayfs)" 1180 help 1181 This option enables support for relay interface support in 1182 certain file systems (such as debugfs). 1183 It is designed to provide an efficient mechanism for tools and 1184 facilities to relay large amounts of data from kernel space to 1185 user space. 1186 1187 If unsure, say N. 1188 1189config BLK_DEV_INITRD 1190 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1191 depends on BROKEN || !FRV 1192 help 1193 The initial RAM filesystem is a ramfs which is loaded by the 1194 boot loader (loadlin or lilo) and that is mounted as root 1195 before the normal boot procedure. It is typically used to 1196 load modules needed to mount the "real" root file system, 1197 etc. See <file:Documentation/initrd.txt> for details. 1198 1199 If RAM disk support (BLK_DEV_RAM) is also included, this 1200 also enables initial RAM disk (initrd) support and adds 1201 15 Kbytes (more on some other architectures) to the kernel size. 1202 1203 If unsure say Y. 1204 1205if BLK_DEV_INITRD 1206 1207source "usr/Kconfig" 1208 1209endif 1210 1211config CC_OPTIMIZE_FOR_SIZE 1212 bool "Optimize for size" 1213 help 1214 Enabling this option will pass "-Os" instead of "-O2" to gcc 1215 resulting in a smaller kernel. 1216 1217 If unsure, say N. 1218 1219config SYSCTL 1220 bool 1221 1222config ANON_INODES 1223 bool 1224 1225config HAVE_UID16 1226 bool 1227 1228config SYSCTL_EXCEPTION_TRACE 1229 bool 1230 help 1231 Enable support for /proc/sys/debug/exception-trace. 1232 1233config SYSCTL_ARCH_UNALIGN_NO_WARN 1234 bool 1235 help 1236 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1237 Allows arch to define/use @no_unaligned_warning to possibly warn 1238 about unaligned access emulation going on under the hood. 1239 1240config SYSCTL_ARCH_UNALIGN_ALLOW 1241 bool 1242 help 1243 Enable support for /proc/sys/kernel/unaligned-trap 1244 Allows arches to define/use @unaligned_enabled to runtime toggle 1245 the unaligned access emulation. 1246 see arch/parisc/kernel/unaligned.c for reference 1247 1248config HOTPLUG 1249 def_bool y 1250 1251config HAVE_PCSPKR_PLATFORM 1252 bool 1253 1254menuconfig EXPERT 1255 bool "Configure standard kernel features (expert users)" 1256 # Unhide debug options, to make the on-by-default options visible 1257 select DEBUG_KERNEL 1258 help 1259 This option allows certain base kernel options and settings 1260 to be disabled or tweaked. This is for specialized 1261 environments which can tolerate a "non-standard" kernel. 1262 Only use this if you really know what you are doing. 1263 1264config UID16 1265 bool "Enable 16-bit UID system calls" if EXPERT 1266 depends on HAVE_UID16 1267 default y 1268 help 1269 This enables the legacy 16-bit UID syscall wrappers. 1270 1271config SYSCTL_SYSCALL 1272 bool "Sysctl syscall support" if EXPERT 1273 depends on PROC_SYSCTL 1274 default n 1275 select SYSCTL 1276 ---help--- 1277 sys_sysctl uses binary paths that have been found challenging 1278 to properly maintain and use. The interface in /proc/sys 1279 using paths with ascii names is now the primary path to this 1280 information. 1281 1282 Almost nothing using the binary sysctl interface so if you are 1283 trying to save some space it is probably safe to disable this, 1284 making your kernel marginally smaller. 1285 1286 If unsure say N here. 1287 1288config KALLSYMS 1289 bool "Load all symbols for debugging/ksymoops" if EXPERT 1290 default y 1291 help 1292 Say Y here to let the kernel print out symbolic crash information and 1293 symbolic stack backtraces. This increases the size of the kernel 1294 somewhat, as all symbols have to be loaded into the kernel image. 1295 1296config KALLSYMS_ALL 1297 bool "Include all symbols in kallsyms" 1298 depends on DEBUG_KERNEL && KALLSYMS 1299 help 1300 Normally kallsyms only contains the symbols of functions for nicer 1301 OOPS messages and backtraces (i.e., symbols from the text and inittext 1302 sections). This is sufficient for most cases. And only in very rare 1303 cases (e.g., when a debugger is used) all symbols are required (e.g., 1304 names of variables from the data sections, etc). 1305 1306 This option makes sure that all symbols are loaded into the kernel 1307 image (i.e., symbols from all sections) in cost of increased kernel 1308 size (depending on the kernel configuration, it may be 300KiB or 1309 something like this). 1310 1311 Say N unless you really need all symbols. 1312 1313config PRINTK 1314 default y 1315 bool "Enable support for printk" if EXPERT 1316 select IRQ_WORK 1317 help 1318 This option enables normal printk support. Removing it 1319 eliminates most of the message strings from the kernel image 1320 and makes the kernel more or less silent. As this makes it 1321 very difficult to diagnose system problems, saying N here is 1322 strongly discouraged. 1323 1324config BUG 1325 bool "BUG() support" if EXPERT 1326 default y 1327 help 1328 Disabling this option eliminates support for BUG and WARN, reducing 1329 the size of your kernel image and potentially quietly ignoring 1330 numerous fatal conditions. You should only consider disabling this 1331 option for embedded systems with no facilities for reporting errors. 1332 Just say Y. 1333 1334config ELF_CORE 1335 depends on COREDUMP 1336 default y 1337 bool "Enable ELF core dumps" if EXPERT 1338 help 1339 Enable support for generating core dumps. Disabling saves about 4k. 1340 1341 1342config PCSPKR_PLATFORM 1343 bool "Enable PC-Speaker support" if EXPERT 1344 depends on HAVE_PCSPKR_PLATFORM 1345 select I8253_LOCK 1346 default y 1347 help 1348 This option allows to disable the internal PC-Speaker 1349 support, saving some memory. 1350 1351config BASE_FULL 1352 default y 1353 bool "Enable full-sized data structures for core" if EXPERT 1354 help 1355 Disabling this option reduces the size of miscellaneous core 1356 kernel data structures. This saves memory on small machines, 1357 but may reduce performance. 1358 1359config FUTEX 1360 bool "Enable futex support" if EXPERT 1361 default y 1362 select RT_MUTEXES 1363 help 1364 Disabling this option will cause the kernel to be built without 1365 support for "fast userspace mutexes". The resulting kernel may not 1366 run glibc-based applications correctly. 1367 1368config EPOLL 1369 bool "Enable eventpoll support" if EXPERT 1370 default y 1371 select ANON_INODES 1372 help 1373 Disabling this option will cause the kernel to be built without 1374 support for epoll family of system calls. 1375 1376config SIGNALFD 1377 bool "Enable signalfd() system call" if EXPERT 1378 select ANON_INODES 1379 default y 1380 help 1381 Enable the signalfd() system call that allows to receive signals 1382 on a file descriptor. 1383 1384 If unsure, say Y. 1385 1386config TIMERFD 1387 bool "Enable timerfd() system call" if EXPERT 1388 select ANON_INODES 1389 default y 1390 help 1391 Enable the timerfd() system call that allows to receive timer 1392 events on a file descriptor. 1393 1394 If unsure, say Y. 1395 1396config EVENTFD 1397 bool "Enable eventfd() system call" if EXPERT 1398 select ANON_INODES 1399 default y 1400 help 1401 Enable the eventfd() system call that allows to receive both 1402 kernel notification (ie. KAIO) or userspace notifications. 1403 1404 If unsure, say Y. 1405 1406config SHMEM 1407 bool "Use full shmem filesystem" if EXPERT 1408 default y 1409 depends on MMU 1410 help 1411 The shmem is an internal filesystem used to manage shared memory. 1412 It is backed by swap and manages resource limits. It is also exported 1413 to userspace as tmpfs if TMPFS is enabled. Disabling this 1414 option replaces shmem and tmpfs with the much simpler ramfs code, 1415 which may be appropriate on small systems without swap. 1416 1417config AIO 1418 bool "Enable AIO support" if EXPERT 1419 default y 1420 help 1421 This option enables POSIX asynchronous I/O which may by used 1422 by some high performance threaded applications. Disabling 1423 this option saves about 7k. 1424 1425config PCI_QUIRKS 1426 default y 1427 bool "Enable PCI quirk workarounds" if EXPERT 1428 depends on PCI 1429 help 1430 This enables workarounds for various PCI chipset 1431 bugs/quirks. Disable this only if your target machine is 1432 unaffected by PCI quirks. 1433 1434config EMBEDDED 1435 bool "Embedded system" 1436 select EXPERT 1437 help 1438 This option should be enabled if compiling the kernel for 1439 an embedded system so certain expert options are available 1440 for configuration. 1441 1442config HAVE_PERF_EVENTS 1443 bool 1444 help 1445 See tools/perf/design.txt for details. 1446 1447config PERF_USE_VMALLOC 1448 bool 1449 help 1450 See tools/perf/design.txt for details 1451 1452menu "Kernel Performance Events And Counters" 1453 1454config PERF_EVENTS 1455 bool "Kernel performance events and counters" 1456 default y if PROFILING 1457 depends on HAVE_PERF_EVENTS 1458 select ANON_INODES 1459 select IRQ_WORK 1460 help 1461 Enable kernel support for various performance events provided 1462 by software and hardware. 1463 1464 Software events are supported either built-in or via the 1465 use of generic tracepoints. 1466 1467 Most modern CPUs support performance events via performance 1468 counter registers. These registers count the number of certain 1469 types of hw events: such as instructions executed, cachemisses 1470 suffered, or branches mis-predicted - without slowing down the 1471 kernel or applications. These registers can also trigger interrupts 1472 when a threshold number of events have passed - and can thus be 1473 used to profile the code that runs on that CPU. 1474 1475 The Linux Performance Event subsystem provides an abstraction of 1476 these software and hardware event capabilities, available via a 1477 system call and used by the "perf" utility in tools/perf/. It 1478 provides per task and per CPU counters, and it provides event 1479 capabilities on top of those. 1480 1481 Say Y if unsure. 1482 1483config DEBUG_PERF_USE_VMALLOC 1484 default n 1485 bool "Debug: use vmalloc to back perf mmap() buffers" 1486 depends on PERF_EVENTS && DEBUG_KERNEL 1487 select PERF_USE_VMALLOC 1488 help 1489 Use vmalloc memory to back perf mmap() buffers. 1490 1491 Mostly useful for debugging the vmalloc code on platforms 1492 that don't require it. 1493 1494 Say N if unsure. 1495 1496endmenu 1497 1498config VM_EVENT_COUNTERS 1499 default y 1500 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1501 help 1502 VM event counters are needed for event counts to be shown. 1503 This option allows the disabling of the VM event counters 1504 on EXPERT systems. /proc/vmstat will only show page counts 1505 if VM event counters are disabled. 1506 1507config SLUB_DEBUG 1508 default y 1509 bool "Enable SLUB debugging support" if EXPERT 1510 depends on SLUB && SYSFS 1511 help 1512 SLUB has extensive debug support features. Disabling these can 1513 result in significant savings in code size. This also disables 1514 SLUB sysfs support. /sys/slab will not exist and there will be 1515 no support for cache validation etc. 1516 1517config COMPAT_BRK 1518 bool "Disable heap randomization" 1519 default y 1520 help 1521 Randomizing heap placement makes heap exploits harder, but it 1522 also breaks ancient binaries (including anything libc5 based). 1523 This option changes the bootup default to heap randomization 1524 disabled, and can be overridden at runtime by setting 1525 /proc/sys/kernel/randomize_va_space to 2. 1526 1527 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1528 1529choice 1530 prompt "Choose SLAB allocator" 1531 default SLUB 1532 help 1533 This option allows to select a slab allocator. 1534 1535config SLAB 1536 bool "SLAB" 1537 help 1538 The regular slab allocator that is established and known to work 1539 well in all environments. It organizes cache hot objects in 1540 per cpu and per node queues. 1541 1542config SLUB 1543 bool "SLUB (Unqueued Allocator)" 1544 help 1545 SLUB is a slab allocator that minimizes cache line usage 1546 instead of managing queues of cached objects (SLAB approach). 1547 Per cpu caching is realized using slabs of objects instead 1548 of queues of objects. SLUB can use memory efficiently 1549 and has enhanced diagnostics. SLUB is the default choice for 1550 a slab allocator. 1551 1552config SLOB 1553 depends on EXPERT 1554 bool "SLOB (Simple Allocator)" 1555 help 1556 SLOB replaces the stock allocator with a drastically simpler 1557 allocator. SLOB is generally more space efficient but 1558 does not perform as well on large systems. 1559 1560endchoice 1561 1562config MMAP_ALLOW_UNINITIALIZED 1563 bool "Allow mmapped anonymous memory to be uninitialized" 1564 depends on EXPERT && !MMU 1565 default n 1566 help 1567 Normally, and according to the Linux spec, anonymous memory obtained 1568 from mmap() has it's contents cleared before it is passed to 1569 userspace. Enabling this config option allows you to request that 1570 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1571 providing a huge performance boost. If this option is not enabled, 1572 then the flag will be ignored. 1573 1574 This is taken advantage of by uClibc's malloc(), and also by 1575 ELF-FDPIC binfmt's brk and stack allocator. 1576 1577 Because of the obvious security issues, this option should only be 1578 enabled on embedded devices where you control what is run in 1579 userspace. Since that isn't generally a problem on no-MMU systems, 1580 it is normally safe to say Y here. 1581 1582 See Documentation/nommu-mmap.txt for more information. 1583 1584config PROFILING 1585 bool "Profiling support" 1586 help 1587 Say Y here to enable the extended profiling support mechanisms used 1588 by profilers such as OProfile. 1589 1590# 1591# Place an empty function call at each tracepoint site. Can be 1592# dynamically changed for a probe function. 1593# 1594config TRACEPOINTS 1595 bool 1596 1597source "arch/Kconfig" 1598 1599endmenu # General setup 1600 1601config HAVE_GENERIC_DMA_COHERENT 1602 bool 1603 default n 1604 1605config SLABINFO 1606 bool 1607 depends on PROC_FS 1608 depends on SLAB || SLUB_DEBUG 1609 default y 1610 1611config RT_MUTEXES 1612 boolean 1613 1614config BASE_SMALL 1615 int 1616 default 0 if BASE_FULL 1617 default 1 if !BASE_FULL 1618 1619menuconfig MODULES 1620 bool "Enable loadable module support" 1621 help 1622 Kernel modules are small pieces of compiled code which can 1623 be inserted in the running kernel, rather than being 1624 permanently built into the kernel. You use the "modprobe" 1625 tool to add (and sometimes remove) them. If you say Y here, 1626 many parts of the kernel can be built as modules (by 1627 answering M instead of Y where indicated): this is most 1628 useful for infrequently used options which are not required 1629 for booting. For more information, see the man pages for 1630 modprobe, lsmod, modinfo, insmod and rmmod. 1631 1632 If you say Y here, you will need to run "make 1633 modules_install" to put the modules under /lib/modules/ 1634 where modprobe can find them (you may need to be root to do 1635 this). 1636 1637 If unsure, say Y. 1638 1639if MODULES 1640 1641config MODULE_FORCE_LOAD 1642 bool "Forced module loading" 1643 default n 1644 help 1645 Allow loading of modules without version information (ie. modprobe 1646 --force). Forced module loading sets the 'F' (forced) taint flag and 1647 is usually a really bad idea. 1648 1649config MODULE_UNLOAD 1650 bool "Module unloading" 1651 help 1652 Without this option you will not be able to unload any 1653 modules (note that some modules may not be unloadable 1654 anyway), which makes your kernel smaller, faster 1655 and simpler. If unsure, say Y. 1656 1657config MODULE_FORCE_UNLOAD 1658 bool "Forced module unloading" 1659 depends on MODULE_UNLOAD 1660 help 1661 This option allows you to force a module to unload, even if the 1662 kernel believes it is unsafe: the kernel will remove the module 1663 without waiting for anyone to stop using it (using the -f option to 1664 rmmod). This is mainly for kernel developers and desperate users. 1665 If unsure, say N. 1666 1667config MODVERSIONS 1668 bool "Module versioning support" 1669 help 1670 Usually, you have to use modules compiled with your kernel. 1671 Saying Y here makes it sometimes possible to use modules 1672 compiled for different kernels, by adding enough information 1673 to the modules to (hopefully) spot any changes which would 1674 make them incompatible with the kernel you are running. If 1675 unsure, say N. 1676 1677config MODULE_SRCVERSION_ALL 1678 bool "Source checksum for all modules" 1679 help 1680 Modules which contain a MODULE_VERSION get an extra "srcversion" 1681 field inserted into their modinfo section, which contains a 1682 sum of the source files which made it. This helps maintainers 1683 see exactly which source was used to build a module (since 1684 others sometimes change the module source without updating 1685 the version). With this option, such a "srcversion" field 1686 will be created for all modules. If unsure, say N. 1687 1688config MODULE_SIG 1689 bool "Module signature verification" 1690 depends on MODULES 1691 select KEYS 1692 select CRYPTO 1693 select ASYMMETRIC_KEY_TYPE 1694 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1695 select PUBLIC_KEY_ALGO_RSA 1696 select ASN1 1697 select OID_REGISTRY 1698 select X509_CERTIFICATE_PARSER 1699 help 1700 Check modules for valid signatures upon load: the signature 1701 is simply appended to the module. For more information see 1702 Documentation/module-signing.txt. 1703 1704 !!!WARNING!!! If you enable this option, you MUST make sure that the 1705 module DOES NOT get stripped after being signed. This includes the 1706 debuginfo strip done by some packagers (such as rpmbuild) and 1707 inclusion into an initramfs that wants the module size reduced. 1708 1709config MODULE_SIG_FORCE 1710 bool "Require modules to be validly signed" 1711 depends on MODULE_SIG 1712 help 1713 Reject unsigned modules or signed modules for which we don't have a 1714 key. Without this, such modules will simply taint the kernel. 1715 1716config MODULE_SIG_ALL 1717 bool "Automatically sign all modules" 1718 default y 1719 depends on MODULE_SIG 1720 help 1721 Sign all modules during make modules_install. Without this option, 1722 modules must be signed manually, using the scripts/sign-file tool. 1723 1724comment "Do not forget to sign required modules with scripts/sign-file" 1725 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1726 1727choice 1728 prompt "Which hash algorithm should modules be signed with?" 1729 depends on MODULE_SIG 1730 help 1731 This determines which sort of hashing algorithm will be used during 1732 signature generation. This algorithm _must_ be built into the kernel 1733 directly so that signature verification can take place. It is not 1734 possible to load a signed module containing the algorithm to check 1735 the signature on that module. 1736 1737config MODULE_SIG_SHA1 1738 bool "Sign modules with SHA-1" 1739 select CRYPTO_SHA1 1740 1741config MODULE_SIG_SHA224 1742 bool "Sign modules with SHA-224" 1743 select CRYPTO_SHA256 1744 1745config MODULE_SIG_SHA256 1746 bool "Sign modules with SHA-256" 1747 select CRYPTO_SHA256 1748 1749config MODULE_SIG_SHA384 1750 bool "Sign modules with SHA-384" 1751 select CRYPTO_SHA512 1752 1753config MODULE_SIG_SHA512 1754 bool "Sign modules with SHA-512" 1755 select CRYPTO_SHA512 1756 1757endchoice 1758 1759config MODULE_SIG_HASH 1760 string 1761 depends on MODULE_SIG 1762 default "sha1" if MODULE_SIG_SHA1 1763 default "sha224" if MODULE_SIG_SHA224 1764 default "sha256" if MODULE_SIG_SHA256 1765 default "sha384" if MODULE_SIG_SHA384 1766 default "sha512" if MODULE_SIG_SHA512 1767 1768endif # MODULES 1769 1770config INIT_ALL_POSSIBLE 1771 bool 1772 help 1773 Back when each arch used to define their own cpu_online_mask and 1774 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1775 with all 1s, and others with all 0s. When they were centralised, 1776 it was better to provide this option than to break all the archs 1777 and have several arch maintainers pursuing me down dark alleys. 1778 1779config STOP_MACHINE 1780 bool 1781 default y 1782 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1783 help 1784 Need stop_machine() primitive. 1785 1786source "block/Kconfig" 1787 1788config PREEMPT_NOTIFIERS 1789 bool 1790 1791config PADATA 1792 depends on SMP 1793 bool 1794 1795# Can be selected by architectures with broken toolchains 1796# that get confused by correct const<->read_only section 1797# mappings 1798config BROKEN_RODATA 1799 bool 1800 1801config ASN1 1802 tristate 1803 help 1804 Build a simple ASN.1 grammar compiler that produces a bytecode output 1805 that can be interpreted by the ASN.1 stream decoder and used to 1806 inform it as to what tags are to be expected in a stream and what 1807 functions to call on what tags. 1808 1809source "kernel/Kconfig.locks" 1810