1config ARCH 2 string 3 option env="ARCH" 4 5config KERNELVERSION 6 string 7 option env="KERNELVERSION" 8 9config DEFCONFIG_LIST 10 string 11 depends on !UML 12 option defconfig_list 13 default "/lib/modules/$UNAME_RELEASE/.config" 14 default "/etc/kernel-config" 15 default "/boot/config-$UNAME_RELEASE" 16 default "$ARCH_DEFCONFIG" 17 default "arch/$ARCH/defconfig" 18 19config CONSTRUCTORS 20 bool 21 depends on !UML 22 23config IRQ_WORK 24 bool 25 26config BUILDTIME_EXTABLE_SORT 27 bool 28 29menu "General setup" 30 31config BROKEN 32 bool 33 34config BROKEN_ON_SMP 35 bool 36 depends on BROKEN || !SMP 37 default y 38 39config INIT_ENV_ARG_LIMIT 40 int 41 default 32 if !UML 42 default 128 if UML 43 help 44 Maximum of each of the number of arguments and environment 45 variables passed to init from the kernel command line. 46 47 48config CROSS_COMPILE 49 string "Cross-compiler tool prefix" 50 help 51 Same as running 'make CROSS_COMPILE=prefix-' but stored for 52 default make runs in this kernel build directory. You don't 53 need to set this unless you want the configured kernel build 54 directory to select the cross-compiler automatically. 55 56config COMPILE_TEST 57 bool "Compile also drivers which will not load" 58 default n 59 help 60 Some drivers can be compiled on a different platform than they are 61 intended to be run on. Despite they cannot be loaded there (or even 62 when they load they cannot be used due to missing HW support), 63 developers still, opposing to distributors, might want to build such 64 drivers to compile-test them. 65 66 If you are a developer and want to build everything available, say Y 67 here. If you are a user/distributor, say N here to exclude useless 68 drivers to be distributed. 69 70config LOCALVERSION 71 string "Local version - append to kernel release" 72 help 73 Append an extra string to the end of your kernel version. 74 This will show up when you type uname, for example. 75 The string you set here will be appended after the contents of 76 any files with a filename matching localversion* in your 77 object and source tree, in that order. Your total string can 78 be a maximum of 64 characters. 79 80config LOCALVERSION_AUTO 81 bool "Automatically append version information to the version string" 82 default y 83 help 84 This will try to automatically determine if the current tree is a 85 release tree by looking for git tags that belong to the current 86 top of tree revision. 87 88 A string of the format -gxxxxxxxx will be added to the localversion 89 if a git-based tree is found. The string generated by this will be 90 appended after any matching localversion* files, and after the value 91 set in CONFIG_LOCALVERSION. 92 93 (The actual string used here is the first eight characters produced 94 by running the command: 95 96 $ git rev-parse --verify HEAD 97 98 which is done within the script "scripts/setlocalversion".) 99 100config HAVE_KERNEL_GZIP 101 bool 102 103config HAVE_KERNEL_BZIP2 104 bool 105 106config HAVE_KERNEL_LZMA 107 bool 108 109config HAVE_KERNEL_XZ 110 bool 111 112config HAVE_KERNEL_LZO 113 bool 114 115choice 116 prompt "Kernel compression mode" 117 default KERNEL_GZIP 118 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO 119 help 120 The linux kernel is a kind of self-extracting executable. 121 Several compression algorithms are available, which differ 122 in efficiency, compression and decompression speed. 123 Compression speed is only relevant when building a kernel. 124 Decompression speed is relevant at each boot. 125 126 If you have any problems with bzip2 or lzma compressed 127 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 128 version of this functionality (bzip2 only), for 2.4, was 129 supplied by Christian Ludwig) 130 131 High compression options are mostly useful for users, who 132 are low on disk space (embedded systems), but for whom ram 133 size matters less. 134 135 If in doubt, select 'gzip' 136 137config KERNEL_GZIP 138 bool "Gzip" 139 depends on HAVE_KERNEL_GZIP 140 help 141 The old and tried gzip compression. It provides a good balance 142 between compression ratio and decompression speed. 143 144config KERNEL_BZIP2 145 bool "Bzip2" 146 depends on HAVE_KERNEL_BZIP2 147 help 148 Its compression ratio and speed is intermediate. 149 Decompression speed is slowest among the choices. The kernel 150 size is about 10% smaller with bzip2, in comparison to gzip. 151 Bzip2 uses a large amount of memory. For modern kernels you 152 will need at least 8MB RAM or more for booting. 153 154config KERNEL_LZMA 155 bool "LZMA" 156 depends on HAVE_KERNEL_LZMA 157 help 158 This compression algorithm's ratio is best. Decompression speed 159 is between gzip and bzip2. Compression is slowest. 160 The kernel size is about 33% smaller with LZMA in comparison to gzip. 161 162config KERNEL_XZ 163 bool "XZ" 164 depends on HAVE_KERNEL_XZ 165 help 166 XZ uses the LZMA2 algorithm and instruction set specific 167 BCJ filters which can improve compression ratio of executable 168 code. The size of the kernel is about 30% smaller with XZ in 169 comparison to gzip. On architectures for which there is a BCJ 170 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ 171 will create a few percent smaller kernel than plain LZMA. 172 173 The speed is about the same as with LZMA: The decompression 174 speed of XZ is better than that of bzip2 but worse than gzip 175 and LZO. Compression is slow. 176 177config KERNEL_LZO 178 bool "LZO" 179 depends on HAVE_KERNEL_LZO 180 help 181 Its compression ratio is the poorest among the choices. The kernel 182 size is about 10% bigger than gzip; however its speed 183 (both compression and decompression) is the fastest. 184 185endchoice 186 187config DEFAULT_HOSTNAME 188 string "Default hostname" 189 default "(none)" 190 help 191 This option determines the default system hostname before userspace 192 calls sethostname(2). The kernel traditionally uses "(none)" here, 193 but you may wish to use a different default here to make a minimal 194 system more usable with less configuration. 195 196config SWAP 197 bool "Support for paging of anonymous memory (swap)" 198 depends on MMU && BLOCK 199 default y 200 help 201 This option allows you to choose whether you want to have support 202 for so called swap devices or swap files in your kernel that are 203 used to provide more virtual memory than the actual RAM present 204 in your computer. If unsure say Y. 205 206config SYSVIPC 207 bool "System V IPC" 208 ---help--- 209 Inter Process Communication is a suite of library functions and 210 system calls which let processes (running programs) synchronize and 211 exchange information. It is generally considered to be a good thing, 212 and some programs won't run unless you say Y here. In particular, if 213 you want to run the DOS emulator dosemu under Linux (read the 214 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 215 you'll need to say Y here. 216 217 You can find documentation about IPC with "info ipc" and also in 218 section 6.4 of the Linux Programmer's Guide, available from 219 <http://www.tldp.org/guides.html>. 220 221config SYSVIPC_SYSCTL 222 bool 223 depends on SYSVIPC 224 depends on SYSCTL 225 default y 226 227config POSIX_MQUEUE 228 bool "POSIX Message Queues" 229 depends on NET 230 ---help--- 231 POSIX variant of message queues is a part of IPC. In POSIX message 232 queues every message has a priority which decides about succession 233 of receiving it by a process. If you want to compile and run 234 programs written e.g. for Solaris with use of its POSIX message 235 queues (functions mq_*) say Y here. 236 237 POSIX message queues are visible as a filesystem called 'mqueue' 238 and can be mounted somewhere if you want to do filesystem 239 operations on message queues. 240 241 If unsure, say Y. 242 243config POSIX_MQUEUE_SYSCTL 244 bool 245 depends on POSIX_MQUEUE 246 depends on SYSCTL 247 default y 248 249config FHANDLE 250 bool "open by fhandle syscalls" 251 select EXPORTFS 252 help 253 If you say Y here, a user level program will be able to map 254 file names to handle and then later use the handle for 255 different file system operations. This is useful in implementing 256 userspace file servers, which now track files using handles instead 257 of names. The handle would remain the same even if file names 258 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) 259 syscalls. 260 261config AUDIT 262 bool "Auditing support" 263 depends on NET 264 help 265 Enable auditing infrastructure that can be used with another 266 kernel subsystem, such as SELinux (which requires this for 267 logging of avc messages output). Does not do system-call 268 auditing without CONFIG_AUDITSYSCALL. 269 270config AUDITSYSCALL 271 bool "Enable system-call auditing support" 272 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT)) 273 default y if SECURITY_SELINUX 274 help 275 Enable low-overhead system-call auditing infrastructure that 276 can be used independently or with another kernel subsystem, 277 such as SELinux. 278 279config AUDIT_WATCH 280 def_bool y 281 depends on AUDITSYSCALL 282 select FSNOTIFY 283 284config AUDIT_TREE 285 def_bool y 286 depends on AUDITSYSCALL 287 select FSNOTIFY 288 289config AUDIT_LOGINUID_IMMUTABLE 290 bool "Make audit loginuid immutable" 291 depends on AUDIT 292 help 293 The config option toggles if a task setting its loginuid requires 294 CAP_SYS_AUDITCONTROL or if that task should require no special permissions 295 but should instead only allow setting its loginuid if it was never 296 previously set. On systems which use systemd or a similar central 297 process to restart login services this should be set to true. On older 298 systems in which an admin would typically have to directly stop and 299 start processes this should be set to false. Setting this to true allows 300 one to drop potentially dangerous capabilites from the login tasks, 301 but may not be backwards compatible with older init systems. 302 303source "kernel/irq/Kconfig" 304source "kernel/time/Kconfig" 305 306menu "CPU/Task time and stats accounting" 307 308config VIRT_CPU_ACCOUNTING 309 bool 310 311choice 312 prompt "Cputime accounting" 313 default TICK_CPU_ACCOUNTING if !PPC64 314 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 315 316# Kind of a stub config for the pure tick based cputime accounting 317config TICK_CPU_ACCOUNTING 318 bool "Simple tick based cputime accounting" 319 depends on !S390 && !NO_HZ_FULL 320 help 321 This is the basic tick based cputime accounting that maintains 322 statistics about user, system and idle time spent on per jiffies 323 granularity. 324 325 If unsure, say Y. 326 327config VIRT_CPU_ACCOUNTING_NATIVE 328 bool "Deterministic task and CPU time accounting" 329 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL 330 select VIRT_CPU_ACCOUNTING 331 help 332 Select this option to enable more accurate task and CPU time 333 accounting. This is done by reading a CPU counter on each 334 kernel entry and exit and on transitions within the kernel 335 between system, softirq and hardirq state, so there is a 336 small performance impact. In the case of s390 or IBM POWER > 5, 337 this also enables accounting of stolen time on logically-partitioned 338 systems. 339 340config VIRT_CPU_ACCOUNTING_GEN 341 bool "Full dynticks CPU time accounting" 342 depends on HAVE_CONTEXT_TRACKING && 64BIT 343 select VIRT_CPU_ACCOUNTING 344 select CONTEXT_TRACKING 345 help 346 Select this option to enable task and CPU time accounting on full 347 dynticks systems. This accounting is implemented by watching every 348 kernel-user boundaries using the context tracking subsystem. 349 The accounting is thus performed at the expense of some significant 350 overhead. 351 352 For now this is only useful if you are working on the full 353 dynticks subsystem development. 354 355 If unsure, say N. 356 357config IRQ_TIME_ACCOUNTING 358 bool "Fine granularity task level IRQ time accounting" 359 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL 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" 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" 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" 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" 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 select IRQ_WORK 449 help 450 This option selects the RCU implementation that is 451 designed for very large SMP system with hundreds or 452 thousands of CPUs. It also scales down nicely to 453 smaller systems. 454 455config TREE_PREEMPT_RCU 456 bool "Preemptible tree-based hierarchical RCU" 457 depends on PREEMPT 458 help 459 This option selects the RCU implementation that is 460 designed for very large SMP systems with hundreds or 461 thousands of CPUs, but for which real-time response 462 is also required. It also scales down nicely to 463 smaller systems. 464 465 Select this option if you are unsure. 466 467config TINY_RCU 468 bool "UP-only small-memory-footprint RCU" 469 depends on !PREEMPT && !SMP 470 help 471 This option selects the RCU implementation that is 472 designed for UP systems from which real-time response 473 is not required. This option greatly reduces the 474 memory footprint of RCU. 475 476endchoice 477 478config PREEMPT_RCU 479 def_bool TREE_PREEMPT_RCU 480 help 481 This option enables preemptible-RCU code that is common between 482 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 483 484config RCU_STALL_COMMON 485 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE ) 486 help 487 This option enables RCU CPU stall code that is common between 488 the TINY and TREE variants of RCU. The purpose is to allow 489 the tiny variants to disable RCU CPU stall warnings, while 490 making these warnings mandatory for the tree variants. 491 492config CONTEXT_TRACKING 493 bool 494 495config RCU_USER_QS 496 bool "Consider userspace as in RCU extended quiescent state" 497 depends on HAVE_CONTEXT_TRACKING && SMP 498 select CONTEXT_TRACKING 499 help 500 This option sets hooks on kernel / userspace boundaries and 501 puts RCU in extended quiescent state when the CPU runs in 502 userspace. It means that when a CPU runs in userspace, it is 503 excluded from the global RCU state machine and thus doesn't 504 try to keep the timer tick on for RCU. 505 506 Unless you want to hack and help the development of the full 507 dynticks mode, you shouldn't enable this option. It also 508 adds unnecessary overhead. 509 510 If unsure say N 511 512config CONTEXT_TRACKING_FORCE 513 bool "Force context tracking" 514 depends on CONTEXT_TRACKING 515 default CONTEXT_TRACKING 516 help 517 Probe on user/kernel boundaries by default in order to 518 test the features that rely on it such as userspace RCU extended 519 quiescent states. 520 This test is there for debugging until we have a real user like the 521 full dynticks mode. 522 523config RCU_FANOUT 524 int "Tree-based hierarchical RCU fanout value" 525 range 2 64 if 64BIT 526 range 2 32 if !64BIT 527 depends on TREE_RCU || TREE_PREEMPT_RCU 528 default 64 if 64BIT 529 default 32 if !64BIT 530 help 531 This option controls the fanout of hierarchical implementations 532 of RCU, allowing RCU to work efficiently on machines with 533 large numbers of CPUs. This value must be at least the fourth 534 root of NR_CPUS, which allows NR_CPUS to be insanely large. 535 The default value of RCU_FANOUT should be used for production 536 systems, but if you are stress-testing the RCU implementation 537 itself, small RCU_FANOUT values allow you to test large-system 538 code paths on small(er) systems. 539 540 Select a specific number if testing RCU itself. 541 Take the default if unsure. 542 543config RCU_FANOUT_LEAF 544 int "Tree-based hierarchical RCU leaf-level fanout value" 545 range 2 RCU_FANOUT if 64BIT 546 range 2 RCU_FANOUT if !64BIT 547 depends on TREE_RCU || TREE_PREEMPT_RCU 548 default 16 549 help 550 This option controls the leaf-level fanout of hierarchical 551 implementations of RCU, and allows trading off cache misses 552 against lock contention. Systems that synchronize their 553 scheduling-clock interrupts for energy-efficiency reasons will 554 want the default because the smaller leaf-level fanout keeps 555 lock contention levels acceptably low. Very large systems 556 (hundreds or thousands of CPUs) will instead want to set this 557 value to the maximum value possible in order to reduce the 558 number of cache misses incurred during RCU's grace-period 559 initialization. These systems tend to run CPU-bound, and thus 560 are not helped by synchronized interrupts, and thus tend to 561 skew them, which reduces lock contention enough that large 562 leaf-level fanouts work well. 563 564 Select a specific number if testing RCU itself. 565 566 Select the maximum permissible value for large systems. 567 568 Take the default if unsure. 569 570config RCU_FANOUT_EXACT 571 bool "Disable tree-based hierarchical RCU auto-balancing" 572 depends on TREE_RCU || TREE_PREEMPT_RCU 573 default n 574 help 575 This option forces use of the exact RCU_FANOUT value specified, 576 regardless of imbalances in the hierarchy. This is useful for 577 testing RCU itself, and might one day be useful on systems with 578 strong NUMA behavior. 579 580 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 581 582 Say N if unsure. 583 584config RCU_FAST_NO_HZ 585 bool "Accelerate last non-dyntick-idle CPU's grace periods" 586 depends on NO_HZ_COMMON && SMP 587 default n 588 help 589 This option permits CPUs to enter dynticks-idle state even if 590 they have RCU callbacks queued, and prevents RCU from waking 591 these CPUs up more than roughly once every four jiffies (by 592 default, you can adjust this using the rcutree.rcu_idle_gp_delay 593 parameter), thus improving energy efficiency. On the other 594 hand, this option increases the duration of RCU grace periods, 595 for example, slowing down synchronize_rcu(). 596 597 Say Y if energy efficiency is critically important, and you 598 don't care about increased grace-period durations. 599 600 Say N if you are unsure. 601 602config TREE_RCU_TRACE 603 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 604 select DEBUG_FS 605 help 606 This option provides tracing for the TREE_RCU and 607 TREE_PREEMPT_RCU implementations, permitting Makefile to 608 trivially select kernel/rcutree_trace.c. 609 610config RCU_BOOST 611 bool "Enable RCU priority boosting" 612 depends on RT_MUTEXES && PREEMPT_RCU 613 default n 614 help 615 This option boosts the priority of preempted RCU readers that 616 block the current preemptible RCU grace period for too long. 617 This option also prevents heavy loads from blocking RCU 618 callback invocation for all flavors of RCU. 619 620 Say Y here if you are working with real-time apps or heavy loads 621 Say N here if you are unsure. 622 623config RCU_BOOST_PRIO 624 int "Real-time priority to boost RCU readers to" 625 range 1 99 626 depends on RCU_BOOST 627 default 1 628 help 629 This option specifies the real-time priority to which long-term 630 preempted RCU readers are to be boosted. If you are working 631 with a real-time application that has one or more CPU-bound 632 threads running at a real-time priority level, you should set 633 RCU_BOOST_PRIO to a priority higher then the highest-priority 634 real-time CPU-bound thread. The default RCU_BOOST_PRIO value 635 of 1 is appropriate in the common case, which is real-time 636 applications that do not have any CPU-bound threads. 637 638 Some real-time applications might not have a single real-time 639 thread that saturates a given CPU, but instead might have 640 multiple real-time threads that, taken together, fully utilize 641 that CPU. In this case, you should set RCU_BOOST_PRIO to 642 a priority higher than the lowest-priority thread that is 643 conspiring to prevent the CPU from running any non-real-time 644 tasks. For example, if one thread at priority 10 and another 645 thread at priority 5 are between themselves fully consuming 646 the CPU time on a given CPU, then RCU_BOOST_PRIO should be 647 set to priority 6 or higher. 648 649 Specify the real-time priority, or take the default if unsure. 650 651config RCU_BOOST_DELAY 652 int "Milliseconds to delay boosting after RCU grace-period start" 653 range 0 3000 654 depends on RCU_BOOST 655 default 500 656 help 657 This option specifies the time to wait after the beginning of 658 a given grace period before priority-boosting preempted RCU 659 readers blocking that grace period. Note that any RCU reader 660 blocking an expedited RCU grace period is boosted immediately. 661 662 Accept the default if unsure. 663 664config RCU_NOCB_CPU 665 bool "Offload RCU callback processing from boot-selected CPUs" 666 depends on TREE_RCU || TREE_PREEMPT_RCU 667 default n 668 help 669 Use this option to reduce OS jitter for aggressive HPC or 670 real-time workloads. It can also be used to offload RCU 671 callback invocation to energy-efficient CPUs in battery-powered 672 asymmetric multiprocessors. 673 674 This option offloads callback invocation from the set of 675 CPUs specified at boot time by the rcu_nocbs parameter. 676 For each such CPU, a kthread ("rcuox/N") will be created to 677 invoke callbacks, where the "N" is the CPU being offloaded, 678 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and 679 "s" for RCU-sched. Nothing prevents this kthread from running 680 on the specified CPUs, but (1) the kthreads may be preempted 681 between each callback, and (2) affinity or cgroups can be used 682 to force the kthreads to run on whatever set of CPUs is desired. 683 684 Say Y here if you want to help to debug reduced OS jitter. 685 Say N here if you are unsure. 686 687choice 688 prompt "Build-forced no-CBs CPUs" 689 default RCU_NOCB_CPU_NONE 690 help 691 This option allows no-CBs CPUs (whose RCU callbacks are invoked 692 from kthreads rather than from softirq context) to be specified 693 at build time. Additional no-CBs CPUs may be specified by 694 the rcu_nocbs= boot parameter. 695 696config RCU_NOCB_CPU_NONE 697 bool "No build_forced no-CBs CPUs" 698 depends on RCU_NOCB_CPU && !NO_HZ_FULL 699 help 700 This option does not force any of the CPUs to be no-CBs CPUs. 701 Only CPUs designated by the rcu_nocbs= boot parameter will be 702 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU 703 kthreads whose names begin with "rcuo". All other CPUs will 704 invoke their own RCU callbacks in softirq context. 705 706 Select this option if you want to choose no-CBs CPUs at 707 boot time, for example, to allow testing of different no-CBs 708 configurations without having to rebuild the kernel each time. 709 710config RCU_NOCB_CPU_ZERO 711 bool "CPU 0 is a build_forced no-CBs CPU" 712 depends on RCU_NOCB_CPU && !NO_HZ_FULL 713 help 714 This option forces CPU 0 to be a no-CBs CPU, so that its RCU 715 callbacks are invoked by a per-CPU kthread whose name begins 716 with "rcuo". Additional CPUs may be designated as no-CBs 717 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. 718 All other CPUs will invoke their own RCU callbacks in softirq 719 context. 720 721 Select this if CPU 0 needs to be a no-CBs CPU for real-time 722 or energy-efficiency reasons, but the real reason it exists 723 is to ensure that randconfig testing covers mixed systems. 724 725config RCU_NOCB_CPU_ALL 726 bool "All CPUs are build_forced no-CBs CPUs" 727 depends on RCU_NOCB_CPU 728 help 729 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= 730 boot parameter will be ignored. All CPUs' RCU callbacks will 731 be executed in the context of per-CPU rcuo kthreads created for 732 this purpose. Assuming that the kthreads whose names start with 733 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter 734 on the remaining CPUs, but might decrease memory locality during 735 RCU-callback invocation, thus potentially degrading throughput. 736 737 Select this if all CPUs need to be no-CBs CPUs for real-time 738 or energy-efficiency reasons. 739 740endchoice 741 742endmenu # "RCU Subsystem" 743 744config IKCONFIG 745 tristate "Kernel .config support" 746 ---help--- 747 This option enables the complete Linux kernel ".config" file 748 contents to be saved in the kernel. It provides documentation 749 of which kernel options are used in a running kernel or in an 750 on-disk kernel. This information can be extracted from the kernel 751 image file with the script scripts/extract-ikconfig and used as 752 input to rebuild the current kernel or to build another kernel. 753 It can also be extracted from a running kernel by reading 754 /proc/config.gz if enabled (below). 755 756config IKCONFIG_PROC 757 bool "Enable access to .config through /proc/config.gz" 758 depends on IKCONFIG && PROC_FS 759 ---help--- 760 This option enables access to the kernel configuration file 761 through /proc/config.gz. 762 763config LOG_BUF_SHIFT 764 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 765 range 12 21 766 default 17 767 help 768 Select kernel log buffer size as a power of 2. 769 Examples: 770 17 => 128 KB 771 16 => 64 KB 772 15 => 32 KB 773 14 => 16 KB 774 13 => 8 KB 775 12 => 4 KB 776 777# 778# Architectures with an unreliable sched_clock() should select this: 779# 780config HAVE_UNSTABLE_SCHED_CLOCK 781 bool 782 783# 784# For architectures that want to enable the support for NUMA-affine scheduler 785# balancing logic: 786# 787config ARCH_SUPPORTS_NUMA_BALANCING 788 bool 789 790# For architectures that (ab)use NUMA to represent different memory regions 791# all cpu-local but of different latencies, such as SuperH. 792# 793config ARCH_WANT_NUMA_VARIABLE_LOCALITY 794 bool 795 796# 797# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE 798config ARCH_WANTS_PROT_NUMA_PROT_NONE 799 bool 800 801config ARCH_USES_NUMA_PROT_NONE 802 bool 803 default y 804 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE 805 depends on NUMA_BALANCING 806 807config NUMA_BALANCING_DEFAULT_ENABLED 808 bool "Automatically enable NUMA aware memory/task placement" 809 default y 810 depends on NUMA_BALANCING 811 help 812 If set, autonumic NUMA balancing will be enabled if running on a NUMA 813 machine. 814 815config NUMA_BALANCING 816 bool "Memory placement aware NUMA scheduler" 817 depends on ARCH_SUPPORTS_NUMA_BALANCING 818 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY 819 depends on SMP && NUMA && MIGRATION 820 help 821 This option adds support for automatic NUMA aware memory/task placement. 822 The mechanism is quite primitive and is based on migrating memory when 823 it is references to the node the task is running on. 824 825 This system will be inactive on UMA systems. 826 827menuconfig CGROUPS 828 boolean "Control Group support" 829 depends on EVENTFD 830 help 831 This option adds support for grouping sets of processes together, for 832 use with process control subsystems such as Cpusets, CFS, memory 833 controls or device isolation. 834 See 835 - Documentation/scheduler/sched-design-CFS.txt (CFS) 836 - Documentation/cgroups/ (features for grouping, isolation 837 and resource control) 838 839 Say N if unsure. 840 841if CGROUPS 842 843config CGROUP_DEBUG 844 bool "Example debug cgroup subsystem" 845 default n 846 help 847 This option enables a simple cgroup subsystem that 848 exports useful debugging information about the cgroups 849 framework. 850 851 Say N if unsure. 852 853config CGROUP_FREEZER 854 bool "Freezer cgroup subsystem" 855 help 856 Provides a way to freeze and unfreeze all tasks in a 857 cgroup. 858 859config CGROUP_DEVICE 860 bool "Device controller for cgroups" 861 help 862 Provides a cgroup implementing whitelists for devices which 863 a process in the cgroup can mknod or open. 864 865config CPUSETS 866 bool "Cpuset support" 867 help 868 This option will let you create and manage CPUSETs which 869 allow dynamically partitioning a system into sets of CPUs and 870 Memory Nodes and assigning tasks to run only within those sets. 871 This is primarily useful on large SMP or NUMA systems. 872 873 Say N if unsure. 874 875config PROC_PID_CPUSET 876 bool "Include legacy /proc/<pid>/cpuset file" 877 depends on CPUSETS 878 default y 879 880config CGROUP_CPUACCT 881 bool "Simple CPU accounting cgroup subsystem" 882 help 883 Provides a simple Resource Controller for monitoring the 884 total CPU consumed by the tasks in a cgroup. 885 886config RESOURCE_COUNTERS 887 bool "Resource counters" 888 help 889 This option enables controller independent resource accounting 890 infrastructure that works with cgroups. 891 892config MEMCG 893 bool "Memory Resource Controller for Control Groups" 894 depends on RESOURCE_COUNTERS 895 select MM_OWNER 896 help 897 Provides a memory resource controller that manages both anonymous 898 memory and page cache. (See Documentation/cgroups/memory.txt) 899 900 Note that setting this option increases fixed memory overhead 901 associated with each page of memory in the system. By this, 902 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 903 usage tracking struct at boot. Total amount of this is printed out 904 at boot. 905 906 Only enable when you're ok with these trade offs and really 907 sure you need the memory resource controller. Even when you enable 908 this, you can set "cgroup_disable=memory" at your boot option to 909 disable memory resource controller and you can avoid overheads. 910 (and lose benefits of memory resource controller) 911 912 This config option also selects MM_OWNER config option, which 913 could in turn add some fork/exit overhead. 914 915config MEMCG_SWAP 916 bool "Memory Resource Controller Swap Extension" 917 depends on MEMCG && SWAP 918 help 919 Add swap management feature to memory resource controller. When you 920 enable this, you can limit mem+swap usage per cgroup. In other words, 921 when you disable this, memory resource controller has no cares to 922 usage of swap...a process can exhaust all of the swap. This extension 923 is useful when you want to avoid exhaustion swap but this itself 924 adds more overheads and consumes memory for remembering information. 925 Especially if you use 32bit system or small memory system, please 926 be careful about enabling this. When memory resource controller 927 is disabled by boot option, this will be automatically disabled and 928 there will be no overhead from this. Even when you set this config=y, 929 if boot option "swapaccount=0" is set, swap will not be accounted. 930 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 931 size is 4096bytes, 512k per 1Gbytes of swap. 932config MEMCG_SWAP_ENABLED 933 bool "Memory Resource Controller Swap Extension enabled by default" 934 depends on MEMCG_SWAP 935 default y 936 help 937 Memory Resource Controller Swap Extension comes with its price in 938 a bigger memory consumption. General purpose distribution kernels 939 which want to enable the feature but keep it disabled by default 940 and let the user enable it by swapaccount boot command line 941 parameter should have this option unselected. 942 For those who want to have the feature enabled by default should 943 select this option (if, for some reason, they need to disable it 944 then swapaccount=0 does the trick). 945config MEMCG_KMEM 946 bool "Memory Resource Controller Kernel Memory accounting" 947 depends on MEMCG 948 depends on SLUB || SLAB 949 help 950 The Kernel Memory extension for Memory Resource Controller can limit 951 the amount of memory used by kernel objects in the system. Those are 952 fundamentally different from the entities handled by the standard 953 Memory Controller, which are page-based, and can be swapped. Users of 954 the kmem extension can use it to guarantee that no group of processes 955 will ever exhaust kernel resources alone. 956 957config CGROUP_HUGETLB 958 bool "HugeTLB Resource Controller for Control Groups" 959 depends on RESOURCE_COUNTERS && HUGETLB_PAGE 960 default n 961 help 962 Provides a cgroup Resource Controller for HugeTLB pages. 963 When you enable this, you can put a per cgroup limit on HugeTLB usage. 964 The limit is enforced during page fault. Since HugeTLB doesn't 965 support page reclaim, enforcing the limit at page fault time implies 966 that, the application will get SIGBUS signal if it tries to access 967 HugeTLB pages beyond its limit. This requires the application to know 968 beforehand how much HugeTLB pages it would require for its use. The 969 control group is tracked in the third page lru pointer. This means 970 that we cannot use the controller with huge page less than 3 pages. 971 972config CGROUP_PERF 973 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring" 974 depends on PERF_EVENTS && CGROUPS 975 help 976 This option extends the per-cpu mode to restrict monitoring to 977 threads which belong to the cgroup specified and run on the 978 designated cpu. 979 980 Say N if unsure. 981 982menuconfig CGROUP_SCHED 983 bool "Group CPU scheduler" 984 default n 985 help 986 This feature lets CPU scheduler recognize task groups and control CPU 987 bandwidth allocation to such task groups. It uses cgroups to group 988 tasks. 989 990if CGROUP_SCHED 991config FAIR_GROUP_SCHED 992 bool "Group scheduling for SCHED_OTHER" 993 depends on CGROUP_SCHED 994 default CGROUP_SCHED 995 996config CFS_BANDWIDTH 997 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" 998 depends on FAIR_GROUP_SCHED 999 default n 1000 help 1001 This option allows users to define CPU bandwidth rates (limits) for 1002 tasks running within the fair group scheduler. Groups with no limit 1003 set are considered to be unconstrained and will run with no 1004 restriction. 1005 See tip/Documentation/scheduler/sched-bwc.txt for more information. 1006 1007config RT_GROUP_SCHED 1008 bool "Group scheduling for SCHED_RR/FIFO" 1009 depends on CGROUP_SCHED 1010 default n 1011 help 1012 This feature lets you explicitly allocate real CPU bandwidth 1013 to task groups. If enabled, it will also make it impossible to 1014 schedule realtime tasks for non-root users until you allocate 1015 realtime bandwidth for them. 1016 See Documentation/scheduler/sched-rt-group.txt for more information. 1017 1018endif #CGROUP_SCHED 1019 1020config BLK_CGROUP 1021 bool "Block IO controller" 1022 depends on BLOCK 1023 default n 1024 ---help--- 1025 Generic block IO controller cgroup interface. This is the common 1026 cgroup interface which should be used by various IO controlling 1027 policies. 1028 1029 Currently, CFQ IO scheduler uses it to recognize task groups and 1030 control disk bandwidth allocation (proportional time slice allocation) 1031 to such task groups. It is also used by bio throttling logic in 1032 block layer to implement upper limit in IO rates on a device. 1033 1034 This option only enables generic Block IO controller infrastructure. 1035 One needs to also enable actual IO controlling logic/policy. For 1036 enabling proportional weight division of disk bandwidth in CFQ, set 1037 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set 1038 CONFIG_BLK_DEV_THROTTLING=y. 1039 1040 See Documentation/cgroups/blkio-controller.txt for more information. 1041 1042config DEBUG_BLK_CGROUP 1043 bool "Enable Block IO controller debugging" 1044 depends on BLK_CGROUP 1045 default n 1046 ---help--- 1047 Enable some debugging help. Currently it exports additional stat 1048 files in a cgroup which can be useful for debugging. 1049 1050endif # CGROUPS 1051 1052config CHECKPOINT_RESTORE 1053 bool "Checkpoint/restore support" if EXPERT 1054 default n 1055 help 1056 Enables additional kernel features in a sake of checkpoint/restore. 1057 In particular it adds auxiliary prctl codes to setup process text, 1058 data and heap segment sizes, and a few additional /proc filesystem 1059 entries. 1060 1061 If unsure, say N here. 1062 1063menuconfig NAMESPACES 1064 bool "Namespaces support" if EXPERT 1065 default !EXPERT 1066 help 1067 Provides the way to make tasks work with different objects using 1068 the same id. For example same IPC id may refer to different objects 1069 or same user id or pid may refer to different tasks when used in 1070 different namespaces. 1071 1072if NAMESPACES 1073 1074config UTS_NS 1075 bool "UTS namespace" 1076 default y 1077 help 1078 In this namespace tasks see different info provided with the 1079 uname() system call 1080 1081config IPC_NS 1082 bool "IPC namespace" 1083 depends on (SYSVIPC || POSIX_MQUEUE) 1084 default y 1085 help 1086 In this namespace tasks work with IPC ids which correspond to 1087 different IPC objects in different namespaces. 1088 1089config USER_NS 1090 bool "User namespace" 1091 depends on UIDGID_CONVERTED 1092 select UIDGID_STRICT_TYPE_CHECKS 1093 1094 default n 1095 help 1096 This allows containers, i.e. vservers, to use user namespaces 1097 to provide different user info for different servers. 1098 1099 When user namespaces are enabled in the kernel it is 1100 recommended that the MEMCG and MEMCG_KMEM options also be 1101 enabled and that user-space use the memory control groups to 1102 limit the amount of memory a memory unprivileged users can 1103 use. 1104 1105 If unsure, say N. 1106 1107config PID_NS 1108 bool "PID Namespaces" 1109 default y 1110 help 1111 Support process id namespaces. This allows having multiple 1112 processes with the same pid as long as they are in different 1113 pid namespaces. This is a building block of containers. 1114 1115config NET_NS 1116 bool "Network namespace" 1117 depends on NET 1118 default y 1119 help 1120 Allow user space to create what appear to be multiple instances 1121 of the network stack. 1122 1123endif # NAMESPACES 1124 1125config UIDGID_CONVERTED 1126 # True if all of the selected software conmponents are known 1127 # to have uid_t and gid_t converted to kuid_t and kgid_t 1128 # where appropriate and are otherwise safe to use with 1129 # the user namespace. 1130 bool 1131 default y 1132 1133 # Filesystems 1134 depends on XFS_FS = n 1135 1136config UIDGID_STRICT_TYPE_CHECKS 1137 bool "Require conversions between uid/gids and their internal representation" 1138 depends on UIDGID_CONVERTED 1139 default n 1140 help 1141 While the nececessary conversions are being added to all subsystems this option allows 1142 the code to continue to build for unconverted subsystems. 1143 1144 Say Y here if you want the strict type checking enabled 1145 1146config SCHED_AUTOGROUP 1147 bool "Automatic process group scheduling" 1148 select EVENTFD 1149 select CGROUPS 1150 select CGROUP_SCHED 1151 select FAIR_GROUP_SCHED 1152 help 1153 This option optimizes the scheduler for common desktop workloads by 1154 automatically creating and populating task groups. This separation 1155 of workloads isolates aggressive CPU burners (like build jobs) from 1156 desktop applications. Task group autogeneration is currently based 1157 upon task session. 1158 1159config MM_OWNER 1160 bool 1161 1162config SYSFS_DEPRECATED 1163 bool "Enable deprecated sysfs features to support old userspace tools" 1164 depends on SYSFS 1165 default n 1166 help 1167 This option adds code that switches the layout of the "block" class 1168 devices, to not show up in /sys/class/block/, but only in 1169 /sys/block/. 1170 1171 This switch is only active when the sysfs.deprecated=1 boot option is 1172 passed or the SYSFS_DEPRECATED_V2 option is set. 1173 1174 This option allows new kernels to run on old distributions and tools, 1175 which might get confused by /sys/class/block/. Since 2007/2008 all 1176 major distributions and tools handle this just fine. 1177 1178 Recent distributions and userspace tools after 2009/2010 depend on 1179 the existence of /sys/class/block/, and will not work with this 1180 option enabled. 1181 1182 Only if you are using a new kernel on an old distribution, you might 1183 need to say Y here. 1184 1185config SYSFS_DEPRECATED_V2 1186 bool "Enable deprecated sysfs features by default" 1187 default n 1188 depends on SYSFS 1189 depends on SYSFS_DEPRECATED 1190 help 1191 Enable deprecated sysfs by default. 1192 1193 See the CONFIG_SYSFS_DEPRECATED option for more details about this 1194 option. 1195 1196 Only if you are using a new kernel on an old distribution, you might 1197 need to say Y here. Even then, odds are you would not need it 1198 enabled, you can always pass the boot option if absolutely necessary. 1199 1200config RELAY 1201 bool "Kernel->user space relay support (formerly relayfs)" 1202 help 1203 This option enables support for relay interface support in 1204 certain file systems (such as debugfs). 1205 It is designed to provide an efficient mechanism for tools and 1206 facilities to relay large amounts of data from kernel space to 1207 user space. 1208 1209 If unsure, say N. 1210 1211config BLK_DEV_INITRD 1212 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 1213 depends on BROKEN || !FRV 1214 help 1215 The initial RAM filesystem is a ramfs which is loaded by the 1216 boot loader (loadlin or lilo) and that is mounted as root 1217 before the normal boot procedure. It is typically used to 1218 load modules needed to mount the "real" root file system, 1219 etc. See <file:Documentation/initrd.txt> for details. 1220 1221 If RAM disk support (BLK_DEV_RAM) is also included, this 1222 also enables initial RAM disk (initrd) support and adds 1223 15 Kbytes (more on some other architectures) to the kernel size. 1224 1225 If unsure say Y. 1226 1227if BLK_DEV_INITRD 1228 1229source "usr/Kconfig" 1230 1231endif 1232 1233config CC_OPTIMIZE_FOR_SIZE 1234 bool "Optimize for size" 1235 help 1236 Enabling this option will pass "-Os" instead of "-O2" to gcc 1237 resulting in a smaller kernel. 1238 1239 If unsure, say N. 1240 1241config SYSCTL 1242 bool 1243 1244config ANON_INODES 1245 bool 1246 1247config HAVE_UID16 1248 bool 1249 1250config SYSCTL_EXCEPTION_TRACE 1251 bool 1252 help 1253 Enable support for /proc/sys/debug/exception-trace. 1254 1255config SYSCTL_ARCH_UNALIGN_NO_WARN 1256 bool 1257 help 1258 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap 1259 Allows arch to define/use @no_unaligned_warning to possibly warn 1260 about unaligned access emulation going on under the hood. 1261 1262config SYSCTL_ARCH_UNALIGN_ALLOW 1263 bool 1264 help 1265 Enable support for /proc/sys/kernel/unaligned-trap 1266 Allows arches to define/use @unaligned_enabled to runtime toggle 1267 the unaligned access emulation. 1268 see arch/parisc/kernel/unaligned.c for reference 1269 1270config HAVE_PCSPKR_PLATFORM 1271 bool 1272 1273menuconfig EXPERT 1274 bool "Configure standard kernel features (expert users)" 1275 # Unhide debug options, to make the on-by-default options visible 1276 select DEBUG_KERNEL 1277 help 1278 This option allows certain base kernel options and settings 1279 to be disabled or tweaked. This is for specialized 1280 environments which can tolerate a "non-standard" kernel. 1281 Only use this if you really know what you are doing. 1282 1283config UID16 1284 bool "Enable 16-bit UID system calls" if EXPERT 1285 depends on HAVE_UID16 1286 default y 1287 help 1288 This enables the legacy 16-bit UID syscall wrappers. 1289 1290config SYSCTL_SYSCALL 1291 bool "Sysctl syscall support" if EXPERT 1292 depends on PROC_SYSCTL 1293 default n 1294 select SYSCTL 1295 ---help--- 1296 sys_sysctl uses binary paths that have been found challenging 1297 to properly maintain and use. The interface in /proc/sys 1298 using paths with ascii names is now the primary path to this 1299 information. 1300 1301 Almost nothing using the binary sysctl interface so if you are 1302 trying to save some space it is probably safe to disable this, 1303 making your kernel marginally smaller. 1304 1305 If unsure say N here. 1306 1307config KALLSYMS 1308 bool "Load all symbols for debugging/ksymoops" if EXPERT 1309 default y 1310 help 1311 Say Y here to let the kernel print out symbolic crash information and 1312 symbolic stack backtraces. This increases the size of the kernel 1313 somewhat, as all symbols have to be loaded into the kernel image. 1314 1315config KALLSYMS_ALL 1316 bool "Include all symbols in kallsyms" 1317 depends on DEBUG_KERNEL && KALLSYMS 1318 help 1319 Normally kallsyms only contains the symbols of functions for nicer 1320 OOPS messages and backtraces (i.e., symbols from the text and inittext 1321 sections). This is sufficient for most cases. And only in very rare 1322 cases (e.g., when a debugger is used) all symbols are required (e.g., 1323 names of variables from the data sections, etc). 1324 1325 This option makes sure that all symbols are loaded into the kernel 1326 image (i.e., symbols from all sections) in cost of increased kernel 1327 size (depending on the kernel configuration, it may be 300KiB or 1328 something like this). 1329 1330 Say N unless you really need all symbols. 1331 1332config PRINTK 1333 default y 1334 bool "Enable support for printk" if EXPERT 1335 select IRQ_WORK 1336 help 1337 This option enables normal printk support. Removing it 1338 eliminates most of the message strings from the kernel image 1339 and makes the kernel more or less silent. As this makes it 1340 very difficult to diagnose system problems, saying N here is 1341 strongly discouraged. 1342 1343config BUG 1344 bool "BUG() support" if EXPERT 1345 default y 1346 help 1347 Disabling this option eliminates support for BUG and WARN, reducing 1348 the size of your kernel image and potentially quietly ignoring 1349 numerous fatal conditions. You should only consider disabling this 1350 option for embedded systems with no facilities for reporting errors. 1351 Just say Y. 1352 1353config ELF_CORE 1354 depends on COREDUMP 1355 default y 1356 bool "Enable ELF core dumps" if EXPERT 1357 help 1358 Enable support for generating core dumps. Disabling saves about 4k. 1359 1360 1361config PCSPKR_PLATFORM 1362 bool "Enable PC-Speaker support" if EXPERT 1363 depends on HAVE_PCSPKR_PLATFORM 1364 select I8253_LOCK 1365 default y 1366 help 1367 This option allows to disable the internal PC-Speaker 1368 support, saving some memory. 1369 1370config BASE_FULL 1371 default y 1372 bool "Enable full-sized data structures for core" if EXPERT 1373 help 1374 Disabling this option reduces the size of miscellaneous core 1375 kernel data structures. This saves memory on small machines, 1376 but may reduce performance. 1377 1378config FUTEX 1379 bool "Enable futex support" if EXPERT 1380 default y 1381 select RT_MUTEXES 1382 help 1383 Disabling this option will cause the kernel to be built without 1384 support for "fast userspace mutexes". The resulting kernel may not 1385 run glibc-based applications correctly. 1386 1387config EPOLL 1388 bool "Enable eventpoll support" if EXPERT 1389 default y 1390 select ANON_INODES 1391 help 1392 Disabling this option will cause the kernel to be built without 1393 support for epoll family of system calls. 1394 1395config SIGNALFD 1396 bool "Enable signalfd() system call" if EXPERT 1397 select ANON_INODES 1398 default y 1399 help 1400 Enable the signalfd() system call that allows to receive signals 1401 on a file descriptor. 1402 1403 If unsure, say Y. 1404 1405config TIMERFD 1406 bool "Enable timerfd() system call" if EXPERT 1407 select ANON_INODES 1408 default y 1409 help 1410 Enable the timerfd() system call that allows to receive timer 1411 events on a file descriptor. 1412 1413 If unsure, say Y. 1414 1415config EVENTFD 1416 bool "Enable eventfd() system call" if EXPERT 1417 select ANON_INODES 1418 default y 1419 help 1420 Enable the eventfd() system call that allows to receive both 1421 kernel notification (ie. KAIO) or userspace notifications. 1422 1423 If unsure, say Y. 1424 1425config SHMEM 1426 bool "Use full shmem filesystem" if EXPERT 1427 default y 1428 depends on MMU 1429 help 1430 The shmem is an internal filesystem used to manage shared memory. 1431 It is backed by swap and manages resource limits. It is also exported 1432 to userspace as tmpfs if TMPFS is enabled. Disabling this 1433 option replaces shmem and tmpfs with the much simpler ramfs code, 1434 which may be appropriate on small systems without swap. 1435 1436config AIO 1437 bool "Enable AIO support" if EXPERT 1438 default y 1439 help 1440 This option enables POSIX asynchronous I/O which may by used 1441 by some high performance threaded applications. Disabling 1442 this option saves about 7k. 1443 1444config PCI_QUIRKS 1445 default y 1446 bool "Enable PCI quirk workarounds" if EXPERT 1447 depends on PCI 1448 help 1449 This enables workarounds for various PCI chipset 1450 bugs/quirks. Disable this only if your target machine is 1451 unaffected by PCI quirks. 1452 1453config EMBEDDED 1454 bool "Embedded system" 1455 select EXPERT 1456 help 1457 This option should be enabled if compiling the kernel for 1458 an embedded system so certain expert options are available 1459 for configuration. 1460 1461config HAVE_PERF_EVENTS 1462 bool 1463 help 1464 See tools/perf/design.txt for details. 1465 1466config PERF_USE_VMALLOC 1467 bool 1468 help 1469 See tools/perf/design.txt for details 1470 1471menu "Kernel Performance Events And Counters" 1472 1473config PERF_EVENTS 1474 bool "Kernel performance events and counters" 1475 default y if PROFILING 1476 depends on HAVE_PERF_EVENTS 1477 select ANON_INODES 1478 select IRQ_WORK 1479 help 1480 Enable kernel support for various performance events provided 1481 by software and hardware. 1482 1483 Software events are supported either built-in or via the 1484 use of generic tracepoints. 1485 1486 Most modern CPUs support performance events via performance 1487 counter registers. These registers count the number of certain 1488 types of hw events: such as instructions executed, cachemisses 1489 suffered, or branches mis-predicted - without slowing down the 1490 kernel or applications. These registers can also trigger interrupts 1491 when a threshold number of events have passed - and can thus be 1492 used to profile the code that runs on that CPU. 1493 1494 The Linux Performance Event subsystem provides an abstraction of 1495 these software and hardware event capabilities, available via a 1496 system call and used by the "perf" utility in tools/perf/. It 1497 provides per task and per CPU counters, and it provides event 1498 capabilities on top of those. 1499 1500 Say Y if unsure. 1501 1502config DEBUG_PERF_USE_VMALLOC 1503 default n 1504 bool "Debug: use vmalloc to back perf mmap() buffers" 1505 depends on PERF_EVENTS && DEBUG_KERNEL 1506 select PERF_USE_VMALLOC 1507 help 1508 Use vmalloc memory to back perf mmap() buffers. 1509 1510 Mostly useful for debugging the vmalloc code on platforms 1511 that don't require it. 1512 1513 Say N if unsure. 1514 1515endmenu 1516 1517config VM_EVENT_COUNTERS 1518 default y 1519 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1520 help 1521 VM event counters are needed for event counts to be shown. 1522 This option allows the disabling of the VM event counters 1523 on EXPERT systems. /proc/vmstat will only show page counts 1524 if VM event counters are disabled. 1525 1526config SLUB_DEBUG 1527 default y 1528 bool "Enable SLUB debugging support" if EXPERT 1529 depends on SLUB && SYSFS 1530 help 1531 SLUB has extensive debug support features. Disabling these can 1532 result in significant savings in code size. This also disables 1533 SLUB sysfs support. /sys/slab will not exist and there will be 1534 no support for cache validation etc. 1535 1536config COMPAT_BRK 1537 bool "Disable heap randomization" 1538 default y 1539 help 1540 Randomizing heap placement makes heap exploits harder, but it 1541 also breaks ancient binaries (including anything libc5 based). 1542 This option changes the bootup default to heap randomization 1543 disabled, and can be overridden at runtime by setting 1544 /proc/sys/kernel/randomize_va_space to 2. 1545 1546 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1547 1548choice 1549 prompt "Choose SLAB allocator" 1550 default SLUB 1551 help 1552 This option allows to select a slab allocator. 1553 1554config SLAB 1555 bool "SLAB" 1556 help 1557 The regular slab allocator that is established and known to work 1558 well in all environments. It organizes cache hot objects in 1559 per cpu and per node queues. 1560 1561config SLUB 1562 bool "SLUB (Unqueued Allocator)" 1563 help 1564 SLUB is a slab allocator that minimizes cache line usage 1565 instead of managing queues of cached objects (SLAB approach). 1566 Per cpu caching is realized using slabs of objects instead 1567 of queues of objects. SLUB can use memory efficiently 1568 and has enhanced diagnostics. SLUB is the default choice for 1569 a slab allocator. 1570 1571config SLOB 1572 depends on EXPERT 1573 bool "SLOB (Simple Allocator)" 1574 help 1575 SLOB replaces the stock allocator with a drastically simpler 1576 allocator. SLOB is generally more space efficient but 1577 does not perform as well on large systems. 1578 1579endchoice 1580 1581config MMAP_ALLOW_UNINITIALIZED 1582 bool "Allow mmapped anonymous memory to be uninitialized" 1583 depends on EXPERT && !MMU 1584 default n 1585 help 1586 Normally, and according to the Linux spec, anonymous memory obtained 1587 from mmap() has it's contents cleared before it is passed to 1588 userspace. Enabling this config option allows you to request that 1589 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1590 providing a huge performance boost. If this option is not enabled, 1591 then the flag will be ignored. 1592 1593 This is taken advantage of by uClibc's malloc(), and also by 1594 ELF-FDPIC binfmt's brk and stack allocator. 1595 1596 Because of the obvious security issues, this option should only be 1597 enabled on embedded devices where you control what is run in 1598 userspace. Since that isn't generally a problem on no-MMU systems, 1599 it is normally safe to say Y here. 1600 1601 See Documentation/nommu-mmap.txt for more information. 1602 1603config PROFILING 1604 bool "Profiling support" 1605 help 1606 Say Y here to enable the extended profiling support mechanisms used 1607 by profilers such as OProfile. 1608 1609# 1610# Place an empty function call at each tracepoint site. Can be 1611# dynamically changed for a probe function. 1612# 1613config TRACEPOINTS 1614 bool 1615 1616source "arch/Kconfig" 1617 1618endmenu # General setup 1619 1620config HAVE_GENERIC_DMA_COHERENT 1621 bool 1622 default n 1623 1624config SLABINFO 1625 bool 1626 depends on PROC_FS 1627 depends on SLAB || SLUB_DEBUG 1628 default y 1629 1630config RT_MUTEXES 1631 boolean 1632 1633config BASE_SMALL 1634 int 1635 default 0 if BASE_FULL 1636 default 1 if !BASE_FULL 1637 1638menuconfig MODULES 1639 bool "Enable loadable module support" 1640 help 1641 Kernel modules are small pieces of compiled code which can 1642 be inserted in the running kernel, rather than being 1643 permanently built into the kernel. You use the "modprobe" 1644 tool to add (and sometimes remove) them. If you say Y here, 1645 many parts of the kernel can be built as modules (by 1646 answering M instead of Y where indicated): this is most 1647 useful for infrequently used options which are not required 1648 for booting. For more information, see the man pages for 1649 modprobe, lsmod, modinfo, insmod and rmmod. 1650 1651 If you say Y here, you will need to run "make 1652 modules_install" to put the modules under /lib/modules/ 1653 where modprobe can find them (you may need to be root to do 1654 this). 1655 1656 If unsure, say Y. 1657 1658if MODULES 1659 1660config MODULE_FORCE_LOAD 1661 bool "Forced module loading" 1662 default n 1663 help 1664 Allow loading of modules without version information (ie. modprobe 1665 --force). Forced module loading sets the 'F' (forced) taint flag and 1666 is usually a really bad idea. 1667 1668config MODULE_UNLOAD 1669 bool "Module unloading" 1670 help 1671 Without this option you will not be able to unload any 1672 modules (note that some modules may not be unloadable 1673 anyway), which makes your kernel smaller, faster 1674 and simpler. If unsure, say Y. 1675 1676config MODULE_FORCE_UNLOAD 1677 bool "Forced module unloading" 1678 depends on MODULE_UNLOAD 1679 help 1680 This option allows you to force a module to unload, even if the 1681 kernel believes it is unsafe: the kernel will remove the module 1682 without waiting for anyone to stop using it (using the -f option to 1683 rmmod). This is mainly for kernel developers and desperate users. 1684 If unsure, say N. 1685 1686config MODVERSIONS 1687 bool "Module versioning support" 1688 help 1689 Usually, you have to use modules compiled with your kernel. 1690 Saying Y here makes it sometimes possible to use modules 1691 compiled for different kernels, by adding enough information 1692 to the modules to (hopefully) spot any changes which would 1693 make them incompatible with the kernel you are running. If 1694 unsure, say N. 1695 1696config MODULE_SRCVERSION_ALL 1697 bool "Source checksum for all modules" 1698 help 1699 Modules which contain a MODULE_VERSION get an extra "srcversion" 1700 field inserted into their modinfo section, which contains a 1701 sum of the source files which made it. This helps maintainers 1702 see exactly which source was used to build a module (since 1703 others sometimes change the module source without updating 1704 the version). With this option, such a "srcversion" field 1705 will be created for all modules. If unsure, say N. 1706 1707config MODULE_SIG 1708 bool "Module signature verification" 1709 depends on MODULES 1710 select KEYS 1711 select CRYPTO 1712 select ASYMMETRIC_KEY_TYPE 1713 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE 1714 select PUBLIC_KEY_ALGO_RSA 1715 select ASN1 1716 select OID_REGISTRY 1717 select X509_CERTIFICATE_PARSER 1718 help 1719 Check modules for valid signatures upon load: the signature 1720 is simply appended to the module. For more information see 1721 Documentation/module-signing.txt. 1722 1723 !!!WARNING!!! If you enable this option, you MUST make sure that the 1724 module DOES NOT get stripped after being signed. This includes the 1725 debuginfo strip done by some packagers (such as rpmbuild) and 1726 inclusion into an initramfs that wants the module size reduced. 1727 1728config MODULE_SIG_FORCE 1729 bool "Require modules to be validly signed" 1730 depends on MODULE_SIG 1731 help 1732 Reject unsigned modules or signed modules for which we don't have a 1733 key. Without this, such modules will simply taint the kernel. 1734 1735config MODULE_SIG_ALL 1736 bool "Automatically sign all modules" 1737 default y 1738 depends on MODULE_SIG 1739 help 1740 Sign all modules during make modules_install. Without this option, 1741 modules must be signed manually, using the scripts/sign-file tool. 1742 1743comment "Do not forget to sign required modules with scripts/sign-file" 1744 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL 1745 1746choice 1747 prompt "Which hash algorithm should modules be signed with?" 1748 depends on MODULE_SIG 1749 help 1750 This determines which sort of hashing algorithm will be used during 1751 signature generation. This algorithm _must_ be built into the kernel 1752 directly so that signature verification can take place. It is not 1753 possible to load a signed module containing the algorithm to check 1754 the signature on that module. 1755 1756config MODULE_SIG_SHA1 1757 bool "Sign modules with SHA-1" 1758 select CRYPTO_SHA1 1759 1760config MODULE_SIG_SHA224 1761 bool "Sign modules with SHA-224" 1762 select CRYPTO_SHA256 1763 1764config MODULE_SIG_SHA256 1765 bool "Sign modules with SHA-256" 1766 select CRYPTO_SHA256 1767 1768config MODULE_SIG_SHA384 1769 bool "Sign modules with SHA-384" 1770 select CRYPTO_SHA512 1771 1772config MODULE_SIG_SHA512 1773 bool "Sign modules with SHA-512" 1774 select CRYPTO_SHA512 1775 1776endchoice 1777 1778config MODULE_SIG_HASH 1779 string 1780 depends on MODULE_SIG 1781 default "sha1" if MODULE_SIG_SHA1 1782 default "sha224" if MODULE_SIG_SHA224 1783 default "sha256" if MODULE_SIG_SHA256 1784 default "sha384" if MODULE_SIG_SHA384 1785 default "sha512" if MODULE_SIG_SHA512 1786 1787endif # MODULES 1788 1789config INIT_ALL_POSSIBLE 1790 bool 1791 help 1792 Back when each arch used to define their own cpu_online_mask and 1793 cpu_possible_mask, some of them chose to initialize cpu_possible_mask 1794 with all 1s, and others with all 0s. When they were centralised, 1795 it was better to provide this option than to break all the archs 1796 and have several arch maintainers pursuing me down dark alleys. 1797 1798config STOP_MACHINE 1799 bool 1800 default y 1801 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1802 help 1803 Need stop_machine() primitive. 1804 1805source "block/Kconfig" 1806 1807config PREEMPT_NOTIFIERS 1808 bool 1809 1810config PADATA 1811 depends on SMP 1812 bool 1813 1814# Can be selected by architectures with broken toolchains 1815# that get confused by correct const<->read_only section 1816# mappings 1817config BROKEN_RODATA 1818 bool 1819 1820config ASN1 1821 tristate 1822 help 1823 Build a simple ASN.1 grammar compiler that produces a bytecode output 1824 that can be interpreted by the ASN.1 stream decoder and used to 1825 inform it as to what tags are to be expected in a stream and what 1826 functions to call on what tags. 1827 1828source "kernel/Kconfig.locks" 1829