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 default y 23 24config HAVE_IRQ_WORK 25 bool 26 27config IRQ_WORK 28 bool 29 depends on HAVE_IRQ_WORK 30 31menu "General setup" 32 33config EXPERIMENTAL 34 bool "Prompt for development and/or incomplete code/drivers" 35 ---help--- 36 Some of the various things that Linux supports (such as network 37 drivers, file systems, network protocols, etc.) can be in a state 38 of development where the functionality, stability, or the level of 39 testing is not yet high enough for general use. This is usually 40 known as the "alpha-test" phase among developers. If a feature is 41 currently in alpha-test, then the developers usually discourage 42 uninformed widespread use of this feature by the general public to 43 avoid "Why doesn't this work?" type mail messages. However, active 44 testing and use of these systems is welcomed. Just be aware that it 45 may not meet the normal level of reliability or it may fail to work 46 in some special cases. Detailed bug reports from people familiar 47 with the kernel internals are usually welcomed by the developers 48 (before submitting bug reports, please read the documents 49 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>, 50 <file:Documentation/BUG-HUNTING>, and 51 <file:Documentation/oops-tracing.txt> in the kernel source). 52 53 This option will also make obsoleted drivers available. These are 54 drivers that have been replaced by something else, and/or are 55 scheduled to be removed in a future kernel release. 56 57 Unless you intend to help test and develop a feature or driver that 58 falls into this category, or you have a situation that requires 59 using these features, you should probably say N here, which will 60 cause the configurator to present you with fewer choices. If 61 you say Y here, you will be offered the choice of using features or 62 drivers that are currently considered to be in the alpha-test phase. 63 64config BROKEN 65 bool 66 67config BROKEN_ON_SMP 68 bool 69 depends on BROKEN || !SMP 70 default y 71 72config LOCK_KERNEL 73 bool 74 depends on (SMP || PREEMPT) && BKL 75 default y 76 77config INIT_ENV_ARG_LIMIT 78 int 79 default 32 if !UML 80 default 128 if UML 81 help 82 Maximum of each of the number of arguments and environment 83 variables passed to init from the kernel command line. 84 85 86config CROSS_COMPILE 87 string "Cross-compiler tool prefix" 88 help 89 Same as running 'make CROSS_COMPILE=prefix-' but stored for 90 default make runs in this kernel build directory. You don't 91 need to set this unless you want the configured kernel build 92 directory to select the cross-compiler automatically. 93 94config LOCALVERSION 95 string "Local version - append to kernel release" 96 help 97 Append an extra string to the end of your kernel version. 98 This will show up when you type uname, for example. 99 The string you set here will be appended after the contents of 100 any files with a filename matching localversion* in your 101 object and source tree, in that order. Your total string can 102 be a maximum of 64 characters. 103 104config LOCALVERSION_AUTO 105 bool "Automatically append version information to the version string" 106 default y 107 help 108 This will try to automatically determine if the current tree is a 109 release tree by looking for git tags that belong to the current 110 top of tree revision. 111 112 A string of the format -gxxxxxxxx will be added to the localversion 113 if a git-based tree is found. The string generated by this will be 114 appended after any matching localversion* files, and after the value 115 set in CONFIG_LOCALVERSION. 116 117 (The actual string used here is the first eight characters produced 118 by running the command: 119 120 $ git rev-parse --verify HEAD 121 122 which is done within the script "scripts/setlocalversion".) 123 124config HAVE_KERNEL_GZIP 125 bool 126 127config HAVE_KERNEL_BZIP2 128 bool 129 130config HAVE_KERNEL_LZMA 131 bool 132 133config HAVE_KERNEL_LZO 134 bool 135 136choice 137 prompt "Kernel compression mode" 138 default KERNEL_GZIP 139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO 140 help 141 The linux kernel is a kind of self-extracting executable. 142 Several compression algorithms are available, which differ 143 in efficiency, compression and decompression speed. 144 Compression speed is only relevant when building a kernel. 145 Decompression speed is relevant at each boot. 146 147 If you have any problems with bzip2 or lzma compressed 148 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older 149 version of this functionality (bzip2 only), for 2.4, was 150 supplied by Christian Ludwig) 151 152 High compression options are mostly useful for users, who 153 are low on disk space (embedded systems), but for whom ram 154 size matters less. 155 156 If in doubt, select 'gzip' 157 158config KERNEL_GZIP 159 bool "Gzip" 160 depends on HAVE_KERNEL_GZIP 161 help 162 The old and tried gzip compression. It provides a good balance 163 between compression ratio and decompression speed. 164 165config KERNEL_BZIP2 166 bool "Bzip2" 167 depends on HAVE_KERNEL_BZIP2 168 help 169 Its compression ratio and speed is intermediate. 170 Decompression speed is slowest among the three. The kernel 171 size is about 10% smaller with bzip2, in comparison to gzip. 172 Bzip2 uses a large amount of memory. For modern kernels you 173 will need at least 8MB RAM or more for booting. 174 175config KERNEL_LZMA 176 bool "LZMA" 177 depends on HAVE_KERNEL_LZMA 178 help 179 The most recent compression algorithm. 180 Its ratio is best, decompression speed is between the other 181 two. Compression is slowest. The kernel size is about 33% 182 smaller with LZMA in comparison to gzip. 183 184config KERNEL_LZO 185 bool "LZO" 186 depends on HAVE_KERNEL_LZO 187 help 188 Its compression ratio is the poorest among the 4. The kernel 189 size is about 10% bigger than gzip; however its speed 190 (both compression and decompression) is the fastest. 191 192endchoice 193 194config SWAP 195 bool "Support for paging of anonymous memory (swap)" 196 depends on MMU && BLOCK 197 default y 198 help 199 This option allows you to choose whether you want to have support 200 for so called swap devices or swap files in your kernel that are 201 used to provide more virtual memory than the actual RAM present 202 in your computer. If unsure say Y. 203 204config SYSVIPC 205 bool "System V IPC" 206 ---help--- 207 Inter Process Communication is a suite of library functions and 208 system calls which let processes (running programs) synchronize and 209 exchange information. It is generally considered to be a good thing, 210 and some programs won't run unless you say Y here. In particular, if 211 you want to run the DOS emulator dosemu under Linux (read the 212 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), 213 you'll need to say Y here. 214 215 You can find documentation about IPC with "info ipc" and also in 216 section 6.4 of the Linux Programmer's Guide, available from 217 <http://www.tldp.org/guides.html>. 218 219config SYSVIPC_SYSCTL 220 bool 221 depends on SYSVIPC 222 depends on SYSCTL 223 default y 224 225config POSIX_MQUEUE 226 bool "POSIX Message Queues" 227 depends on NET && EXPERIMENTAL 228 ---help--- 229 POSIX variant of message queues is a part of IPC. In POSIX message 230 queues every message has a priority which decides about succession 231 of receiving it by a process. If you want to compile and run 232 programs written e.g. for Solaris with use of its POSIX message 233 queues (functions mq_*) say Y here. 234 235 POSIX message queues are visible as a filesystem called 'mqueue' 236 and can be mounted somewhere if you want to do filesystem 237 operations on message queues. 238 239 If unsure, say Y. 240 241config POSIX_MQUEUE_SYSCTL 242 bool 243 depends on POSIX_MQUEUE 244 depends on SYSCTL 245 default y 246 247config BSD_PROCESS_ACCT 248 bool "BSD Process Accounting" 249 help 250 If you say Y here, a user level program will be able to instruct the 251 kernel (via a special system call) to write process accounting 252 information to a file: whenever a process exits, information about 253 that process will be appended to the file by the kernel. The 254 information includes things such as creation time, owning user, 255 command name, memory usage, controlling terminal etc. (the complete 256 list is in the struct acct in <file:include/linux/acct.h>). It is 257 up to the user level program to do useful things with this 258 information. This is generally a good idea, so say Y. 259 260config BSD_PROCESS_ACCT_V3 261 bool "BSD Process Accounting version 3 file format" 262 depends on BSD_PROCESS_ACCT 263 default n 264 help 265 If you say Y here, the process accounting information is written 266 in a new file format that also logs the process IDs of each 267 process and it's parent. Note that this file format is incompatible 268 with previous v0/v1/v2 file formats, so you will need updated tools 269 for processing it. A preliminary version of these tools is available 270 at <http://www.gnu.org/software/acct/>. 271 272config TASKSTATS 273 bool "Export task/process statistics through netlink (EXPERIMENTAL)" 274 depends on NET 275 default n 276 help 277 Export selected statistics for tasks/processes through the 278 generic netlink interface. Unlike BSD process accounting, the 279 statistics are available during the lifetime of tasks/processes as 280 responses to commands. Like BSD accounting, they are sent to user 281 space on task exit. 282 283 Say N if unsure. 284 285config TASK_DELAY_ACCT 286 bool "Enable per-task delay accounting (EXPERIMENTAL)" 287 depends on TASKSTATS 288 help 289 Collect information on time spent by a task waiting for system 290 resources like cpu, synchronous block I/O completion and swapping 291 in pages. Such statistics can help in setting a task's priorities 292 relative to other tasks for cpu, io, rss limits etc. 293 294 Say N if unsure. 295 296config TASK_XACCT 297 bool "Enable extended accounting over taskstats (EXPERIMENTAL)" 298 depends on TASKSTATS 299 help 300 Collect extended task accounting data and send the data 301 to userland for processing over the taskstats interface. 302 303 Say N if unsure. 304 305config TASK_IO_ACCOUNTING 306 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)" 307 depends on TASK_XACCT 308 help 309 Collect information on the number of bytes of storage I/O which this 310 task has caused. 311 312 Say N if unsure. 313 314config AUDIT 315 bool "Auditing support" 316 depends on NET 317 help 318 Enable auditing infrastructure that can be used with another 319 kernel subsystem, such as SELinux (which requires this for 320 logging of avc messages output). Does not do system-call 321 auditing without CONFIG_AUDITSYSCALL. 322 323config AUDITSYSCALL 324 bool "Enable system-call auditing support" 325 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH) 326 default y if SECURITY_SELINUX 327 help 328 Enable low-overhead system-call auditing infrastructure that 329 can be used independently or with another kernel subsystem, 330 such as SELinux. 331 332config AUDIT_WATCH 333 def_bool y 334 depends on AUDITSYSCALL 335 select FSNOTIFY 336 337config AUDIT_TREE 338 def_bool y 339 depends on AUDITSYSCALL 340 select FSNOTIFY 341 342source "kernel/irq/Kconfig" 343 344menu "RCU Subsystem" 345 346choice 347 prompt "RCU Implementation" 348 default TREE_RCU 349 350config TREE_RCU 351 bool "Tree-based hierarchical RCU" 352 depends on !PREEMPT && SMP 353 help 354 This option selects the RCU implementation that is 355 designed for very large SMP system with hundreds or 356 thousands of CPUs. It also scales down nicely to 357 smaller systems. 358 359config TREE_PREEMPT_RCU 360 bool "Preemptible tree-based hierarchical RCU" 361 depends on PREEMPT 362 help 363 This option selects the RCU implementation that is 364 designed for very large SMP systems with hundreds or 365 thousands of CPUs, but for which real-time response 366 is also required. It also scales down nicely to 367 smaller systems. 368 369config TINY_RCU 370 bool "UP-only small-memory-footprint RCU" 371 depends on !SMP 372 help 373 This option selects the RCU implementation that is 374 designed for UP systems from which real-time response 375 is not required. This option greatly reduces the 376 memory footprint of RCU. 377 378config TINY_PREEMPT_RCU 379 bool "Preemptible UP-only small-memory-footprint RCU" 380 depends on !SMP && PREEMPT 381 help 382 This option selects the RCU implementation that is designed 383 for real-time UP systems. This option greatly reduces the 384 memory footprint of RCU. 385 386endchoice 387 388config PREEMPT_RCU 389 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU ) 390 help 391 This option enables preemptible-RCU code that is common between 392 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations. 393 394config RCU_TRACE 395 bool "Enable tracing for RCU" 396 depends on TREE_RCU || TREE_PREEMPT_RCU 397 help 398 This option provides tracing in RCU which presents stats 399 in debugfs for debugging RCU implementation. 400 401 Say Y here if you want to enable RCU tracing 402 Say N if you are unsure. 403 404config RCU_FANOUT 405 int "Tree-based hierarchical RCU fanout value" 406 range 2 64 if 64BIT 407 range 2 32 if !64BIT 408 depends on TREE_RCU || TREE_PREEMPT_RCU 409 default 64 if 64BIT 410 default 32 if !64BIT 411 help 412 This option controls the fanout of hierarchical implementations 413 of RCU, allowing RCU to work efficiently on machines with 414 large numbers of CPUs. This value must be at least the fourth 415 root of NR_CPUS, which allows NR_CPUS to be insanely large. 416 The default value of RCU_FANOUT should be used for production 417 systems, but if you are stress-testing the RCU implementation 418 itself, small RCU_FANOUT values allow you to test large-system 419 code paths on small(er) systems. 420 421 Select a specific number if testing RCU itself. 422 Take the default if unsure. 423 424config RCU_FANOUT_EXACT 425 bool "Disable tree-based hierarchical RCU auto-balancing" 426 depends on TREE_RCU || TREE_PREEMPT_RCU 427 default n 428 help 429 This option forces use of the exact RCU_FANOUT value specified, 430 regardless of imbalances in the hierarchy. This is useful for 431 testing RCU itself, and might one day be useful on systems with 432 strong NUMA behavior. 433 434 Without RCU_FANOUT_EXACT, the code will balance the hierarchy. 435 436 Say N if unsure. 437 438config RCU_FAST_NO_HZ 439 bool "Accelerate last non-dyntick-idle CPU's grace periods" 440 depends on TREE_RCU && NO_HZ && SMP 441 default n 442 help 443 This option causes RCU to attempt to accelerate grace periods 444 in order to allow the final CPU to enter dynticks-idle state 445 more quickly. On the other hand, this option increases the 446 overhead of the dynticks-idle checking, particularly on systems 447 with large numbers of CPUs. 448 449 Say Y if energy efficiency is critically important, particularly 450 if you have relatively few CPUs. 451 452 Say N if you are unsure. 453 454config TREE_RCU_TRACE 455 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) 456 select DEBUG_FS 457 help 458 This option provides tracing for the TREE_RCU and 459 TREE_PREEMPT_RCU implementations, permitting Makefile to 460 trivially select kernel/rcutree_trace.c. 461 462endmenu # "RCU Subsystem" 463 464config IKCONFIG 465 tristate "Kernel .config support" 466 ---help--- 467 This option enables the complete Linux kernel ".config" file 468 contents to be saved in the kernel. It provides documentation 469 of which kernel options are used in a running kernel or in an 470 on-disk kernel. This information can be extracted from the kernel 471 image file with the script scripts/extract-ikconfig and used as 472 input to rebuild the current kernel or to build another kernel. 473 It can also be extracted from a running kernel by reading 474 /proc/config.gz if enabled (below). 475 476config IKCONFIG_PROC 477 bool "Enable access to .config through /proc/config.gz" 478 depends on IKCONFIG && PROC_FS 479 ---help--- 480 This option enables access to the kernel configuration file 481 through /proc/config.gz. 482 483config LOG_BUF_SHIFT 484 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" 485 range 12 21 486 default 17 487 help 488 Select kernel log buffer size as a power of 2. 489 Examples: 490 17 => 128 KB 491 16 => 64 KB 492 15 => 32 KB 493 14 => 16 KB 494 13 => 8 KB 495 12 => 4 KB 496 497# 498# Architectures with an unreliable sched_clock() should select this: 499# 500config HAVE_UNSTABLE_SCHED_CLOCK 501 bool 502 503menuconfig CGROUPS 504 boolean "Control Group support" 505 depends on EVENTFD 506 help 507 This option adds support for grouping sets of processes together, for 508 use with process control subsystems such as Cpusets, CFS, memory 509 controls or device isolation. 510 See 511 - Documentation/scheduler/sched-design-CFS.txt (CFS) 512 - Documentation/cgroups/ (features for grouping, isolation 513 and resource control) 514 515 Say N if unsure. 516 517if CGROUPS 518 519config CGROUP_DEBUG 520 bool "Example debug cgroup subsystem" 521 default n 522 help 523 This option enables a simple cgroup subsystem that 524 exports useful debugging information about the cgroups 525 framework. 526 527 Say N if unsure. 528 529config CGROUP_NS 530 bool "Namespace cgroup subsystem" 531 help 532 Provides a simple namespace cgroup subsystem to 533 provide hierarchical naming of sets of namespaces, 534 for instance virtual servers and checkpoint/restart 535 jobs. 536 537config CGROUP_FREEZER 538 bool "Freezer cgroup subsystem" 539 help 540 Provides a way to freeze and unfreeze all tasks in a 541 cgroup. 542 543config CGROUP_DEVICE 544 bool "Device controller for cgroups" 545 help 546 Provides a cgroup implementing whitelists for devices which 547 a process in the cgroup can mknod or open. 548 549config CPUSETS 550 bool "Cpuset support" 551 help 552 This option will let you create and manage CPUSETs which 553 allow dynamically partitioning a system into sets of CPUs and 554 Memory Nodes and assigning tasks to run only within those sets. 555 This is primarily useful on large SMP or NUMA systems. 556 557 Say N if unsure. 558 559config PROC_PID_CPUSET 560 bool "Include legacy /proc/<pid>/cpuset file" 561 depends on CPUSETS 562 default y 563 564config CGROUP_CPUACCT 565 bool "Simple CPU accounting cgroup subsystem" 566 help 567 Provides a simple Resource Controller for monitoring the 568 total CPU consumed by the tasks in a cgroup. 569 570config RESOURCE_COUNTERS 571 bool "Resource counters" 572 help 573 This option enables controller independent resource accounting 574 infrastructure that works with cgroups. 575 576config CGROUP_MEM_RES_CTLR 577 bool "Memory Resource Controller for Control Groups" 578 depends on RESOURCE_COUNTERS 579 select MM_OWNER 580 help 581 Provides a memory resource controller that manages both anonymous 582 memory and page cache. (See Documentation/cgroups/memory.txt) 583 584 Note that setting this option increases fixed memory overhead 585 associated with each page of memory in the system. By this, 586 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory 587 usage tracking struct at boot. Total amount of this is printed out 588 at boot. 589 590 Only enable when you're ok with these trade offs and really 591 sure you need the memory resource controller. Even when you enable 592 this, you can set "cgroup_disable=memory" at your boot option to 593 disable memory resource controller and you can avoid overheads. 594 (and lose benefits of memory resource controller) 595 596 This config option also selects MM_OWNER config option, which 597 could in turn add some fork/exit overhead. 598 599config CGROUP_MEM_RES_CTLR_SWAP 600 bool "Memory Resource Controller Swap Extension" 601 depends on CGROUP_MEM_RES_CTLR && SWAP 602 help 603 Add swap management feature to memory resource controller. When you 604 enable this, you can limit mem+swap usage per cgroup. In other words, 605 when you disable this, memory resource controller has no cares to 606 usage of swap...a process can exhaust all of the swap. This extension 607 is useful when you want to avoid exhaustion swap but this itself 608 adds more overheads and consumes memory for remembering information. 609 Especially if you use 32bit system or small memory system, please 610 be careful about enabling this. When memory resource controller 611 is disabled by boot option, this will be automatically disabled and 612 there will be no overhead from this. Even when you set this config=y, 613 if boot option "noswapaccount" is set, swap will not be accounted. 614 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page 615 size is 4096bytes, 512k per 1Gbytes of swap. 616config CGROUP_MEM_RES_CTLR_SWAP_ENABLED 617 bool "Memory Resource Controller Swap Extension enabled by default" 618 depends on CGROUP_MEM_RES_CTLR_SWAP 619 default y 620 help 621 Memory Resource Controller Swap Extension comes with its price in 622 a bigger memory consumption. General purpose distribution kernels 623 which want to enable the feautre but keep it disabled by default 624 and let the user enable it by swapaccount boot command line 625 parameter should have this option unselected. 626 For those who want to have the feature enabled by default should 627 select this option (if, for some reason, they need to disable it 628 then noswapaccount does the trick). 629 630menuconfig CGROUP_SCHED 631 bool "Group CPU scheduler" 632 depends on EXPERIMENTAL 633 default n 634 help 635 This feature lets CPU scheduler recognize task groups and control CPU 636 bandwidth allocation to such task groups. It uses cgroups to group 637 tasks. 638 639if CGROUP_SCHED 640config FAIR_GROUP_SCHED 641 bool "Group scheduling for SCHED_OTHER" 642 depends on CGROUP_SCHED 643 default CGROUP_SCHED 644 645config RT_GROUP_SCHED 646 bool "Group scheduling for SCHED_RR/FIFO" 647 depends on EXPERIMENTAL 648 depends on CGROUP_SCHED 649 default n 650 help 651 This feature lets you explicitly allocate real CPU bandwidth 652 to task groups. If enabled, it will also make it impossible to 653 schedule realtime tasks for non-root users until you allocate 654 realtime bandwidth for them. 655 See Documentation/scheduler/sched-rt-group.txt for more information. 656 657endif #CGROUP_SCHED 658 659config BLK_CGROUP 660 tristate "Block IO controller" 661 depends on BLOCK 662 default n 663 ---help--- 664 Generic block IO controller cgroup interface. This is the common 665 cgroup interface which should be used by various IO controlling 666 policies. 667 668 Currently, CFQ IO scheduler uses it to recognize task groups and 669 control disk bandwidth allocation (proportional time slice allocation) 670 to such task groups. It is also used by bio throttling logic in 671 block layer to implement upper limit in IO rates on a device. 672 673 This option only enables generic Block IO controller infrastructure. 674 One needs to also enable actual IO controlling logic/policy. For 675 enabling proportional weight division of disk bandwidth in CFQ seti 676 CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set 677 CONFIG_BLK_THROTTLE=y. 678 679 See Documentation/cgroups/blkio-controller.txt for more information. 680 681config DEBUG_BLK_CGROUP 682 bool "Enable Block IO controller debugging" 683 depends on BLK_CGROUP 684 default n 685 ---help--- 686 Enable some debugging help. Currently it exports additional stat 687 files in a cgroup which can be useful for debugging. 688 689endif # CGROUPS 690 691menuconfig NAMESPACES 692 bool "Namespaces support" if EMBEDDED 693 default !EMBEDDED 694 help 695 Provides the way to make tasks work with different objects using 696 the same id. For example same IPC id may refer to different objects 697 or same user id or pid may refer to different tasks when used in 698 different namespaces. 699 700if NAMESPACES 701 702config UTS_NS 703 bool "UTS namespace" 704 default y 705 help 706 In this namespace tasks see different info provided with the 707 uname() system call 708 709config IPC_NS 710 bool "IPC namespace" 711 depends on (SYSVIPC || POSIX_MQUEUE) 712 default y 713 help 714 In this namespace tasks work with IPC ids which correspond to 715 different IPC objects in different namespaces. 716 717config USER_NS 718 bool "User namespace (EXPERIMENTAL)" 719 depends on EXPERIMENTAL 720 default y 721 help 722 This allows containers, i.e. vservers, to use user namespaces 723 to provide different user info for different servers. 724 If unsure, say N. 725 726config PID_NS 727 bool "PID Namespaces" 728 default y 729 help 730 Support process id namespaces. This allows having multiple 731 processes with the same pid as long as they are in different 732 pid namespaces. This is a building block of containers. 733 734config NET_NS 735 bool "Network namespace" 736 depends on NET 737 default y 738 help 739 Allow user space to create what appear to be multiple instances 740 of the network stack. 741 742endif # NAMESPACES 743 744config MM_OWNER 745 bool 746 747config SYSFS_DEPRECATED 748 bool "enable deprecated sysfs features to support old userspace tools" 749 depends on SYSFS 750 default n 751 help 752 This option adds code that switches the layout of the "block" class 753 devices, to not show up in /sys/class/block/, but only in 754 /sys/block/. 755 756 This switch is only active when the sysfs.deprecated=1 boot option is 757 passed or the SYSFS_DEPRECATED_V2 option is set. 758 759 This option allows new kernels to run on old distributions and tools, 760 which might get confused by /sys/class/block/. Since 2007/2008 all 761 major distributions and tools handle this just fine. 762 763 Recent distributions and userspace tools after 2009/2010 depend on 764 the existence of /sys/class/block/, and will not work with this 765 option enabled. 766 767 Only if you are using a new kernel on an old distribution, you might 768 need to say Y here. 769 770config SYSFS_DEPRECATED_V2 771 bool "enabled deprecated sysfs features by default" 772 default n 773 depends on SYSFS 774 depends on SYSFS_DEPRECATED 775 help 776 Enable deprecated sysfs by default. 777 778 See the CONFIG_SYSFS_DEPRECATED option for more details about this 779 option. 780 781 Only if you are using a new kernel on an old distribution, you might 782 need to say Y here. Even then, odds are you would not need it 783 enabled, you can always pass the boot option if absolutely necessary. 784 785config RELAY 786 bool "Kernel->user space relay support (formerly relayfs)" 787 help 788 This option enables support for relay interface support in 789 certain file systems (such as debugfs). 790 It is designed to provide an efficient mechanism for tools and 791 facilities to relay large amounts of data from kernel space to 792 user space. 793 794 If unsure, say N. 795 796config BLK_DEV_INITRD 797 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" 798 depends on BROKEN || !FRV 799 help 800 The initial RAM filesystem is a ramfs which is loaded by the 801 boot loader (loadlin or lilo) and that is mounted as root 802 before the normal boot procedure. It is typically used to 803 load modules needed to mount the "real" root file system, 804 etc. See <file:Documentation/initrd.txt> for details. 805 806 If RAM disk support (BLK_DEV_RAM) is also included, this 807 also enables initial RAM disk (initrd) support and adds 808 15 Kbytes (more on some other architectures) to the kernel size. 809 810 If unsure say Y. 811 812if BLK_DEV_INITRD 813 814source "usr/Kconfig" 815 816endif 817 818config CC_OPTIMIZE_FOR_SIZE 819 bool "Optimize for size" 820 default y 821 help 822 Enabling this option will pass "-Os" instead of "-O2" to gcc 823 resulting in a smaller kernel. 824 825 If unsure, say Y. 826 827config SYSCTL 828 bool 829 830config ANON_INODES 831 bool 832 833menuconfig EMBEDDED 834 bool "Configure standard kernel features (for small systems)" 835 help 836 This option allows certain base kernel options and settings 837 to be disabled or tweaked. This is for specialized 838 environments which can tolerate a "non-standard" kernel. 839 Only use this if you really know what you are doing. 840 841config UID16 842 bool "Enable 16-bit UID system calls" if EMBEDDED 843 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION) 844 default y 845 help 846 This enables the legacy 16-bit UID syscall wrappers. 847 848config SYSCTL_SYSCALL 849 bool "Sysctl syscall support" if EMBEDDED 850 depends on PROC_SYSCTL 851 default y 852 select SYSCTL 853 ---help--- 854 sys_sysctl uses binary paths that have been found challenging 855 to properly maintain and use. The interface in /proc/sys 856 using paths with ascii names is now the primary path to this 857 information. 858 859 Almost nothing using the binary sysctl interface so if you are 860 trying to save some space it is probably safe to disable this, 861 making your kernel marginally smaller. 862 863 If unsure say Y here. 864 865config KALLSYMS 866 bool "Load all symbols for debugging/ksymoops" if EMBEDDED 867 default y 868 help 869 Say Y here to let the kernel print out symbolic crash information and 870 symbolic stack backtraces. This increases the size of the kernel 871 somewhat, as all symbols have to be loaded into the kernel image. 872 873config KALLSYMS_ALL 874 bool "Include all symbols in kallsyms" 875 depends on DEBUG_KERNEL && KALLSYMS 876 help 877 Normally kallsyms only contains the symbols of functions, for nicer 878 OOPS messages. Some debuggers can use kallsyms for other 879 symbols too: say Y here to include all symbols, if you need them 880 and you don't care about adding 300k to the size of your kernel. 881 882 Say N. 883 884config KALLSYMS_EXTRA_PASS 885 bool "Do an extra kallsyms pass" 886 depends on KALLSYMS 887 help 888 If kallsyms is not working correctly, the build will fail with 889 inconsistent kallsyms data. If that occurs, log a bug report and 890 turn on KALLSYMS_EXTRA_PASS which should result in a stable build. 891 Always say N here unless you find a bug in kallsyms, which must be 892 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while 893 you wait for kallsyms to be fixed. 894 895 896config HOTPLUG 897 bool "Support for hot-pluggable devices" if EMBEDDED 898 default y 899 help 900 This option is provided for the case where no hotplug or uevent 901 capabilities is wanted by the kernel. You should only consider 902 disabling this option for embedded systems that do not use modules, a 903 dynamic /dev tree, or dynamic device discovery. Just say Y. 904 905config PRINTK 906 default y 907 bool "Enable support for printk" if EMBEDDED 908 help 909 This option enables normal printk support. Removing it 910 eliminates most of the message strings from the kernel image 911 and makes the kernel more or less silent. As this makes it 912 very difficult to diagnose system problems, saying N here is 913 strongly discouraged. 914 915config BUG 916 bool "BUG() support" if EMBEDDED 917 default y 918 help 919 Disabling this option eliminates support for BUG and WARN, reducing 920 the size of your kernel image and potentially quietly ignoring 921 numerous fatal conditions. You should only consider disabling this 922 option for embedded systems with no facilities for reporting errors. 923 Just say Y. 924 925config ELF_CORE 926 default y 927 bool "Enable ELF core dumps" if EMBEDDED 928 help 929 Enable support for generating core dumps. Disabling saves about 4k. 930 931config PCSPKR_PLATFORM 932 bool "Enable PC-Speaker support" if EMBEDDED 933 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES 934 default y 935 help 936 This option allows to disable the internal PC-Speaker 937 support, saving some memory. 938 939config BASE_FULL 940 default y 941 bool "Enable full-sized data structures for core" if EMBEDDED 942 help 943 Disabling this option reduces the size of miscellaneous core 944 kernel data structures. This saves memory on small machines, 945 but may reduce performance. 946 947config FUTEX 948 bool "Enable futex support" if EMBEDDED 949 default y 950 select RT_MUTEXES 951 help 952 Disabling this option will cause the kernel to be built without 953 support for "fast userspace mutexes". The resulting kernel may not 954 run glibc-based applications correctly. 955 956config EPOLL 957 bool "Enable eventpoll support" if EMBEDDED 958 default y 959 select ANON_INODES 960 help 961 Disabling this option will cause the kernel to be built without 962 support for epoll family of system calls. 963 964config SIGNALFD 965 bool "Enable signalfd() system call" if EMBEDDED 966 select ANON_INODES 967 default y 968 help 969 Enable the signalfd() system call that allows to receive signals 970 on a file descriptor. 971 972 If unsure, say Y. 973 974config TIMERFD 975 bool "Enable timerfd() system call" if EMBEDDED 976 select ANON_INODES 977 default y 978 help 979 Enable the timerfd() system call that allows to receive timer 980 events on a file descriptor. 981 982 If unsure, say Y. 983 984config EVENTFD 985 bool "Enable eventfd() system call" if EMBEDDED 986 select ANON_INODES 987 default y 988 help 989 Enable the eventfd() system call that allows to receive both 990 kernel notification (ie. KAIO) or userspace notifications. 991 992 If unsure, say Y. 993 994config SHMEM 995 bool "Use full shmem filesystem" if EMBEDDED 996 default y 997 depends on MMU 998 help 999 The shmem is an internal filesystem used to manage shared memory. 1000 It is backed by swap and manages resource limits. It is also exported 1001 to userspace as tmpfs if TMPFS is enabled. Disabling this 1002 option replaces shmem and tmpfs with the much simpler ramfs code, 1003 which may be appropriate on small systems without swap. 1004 1005config AIO 1006 bool "Enable AIO support" if EMBEDDED 1007 default y 1008 help 1009 This option enables POSIX asynchronous I/O which may by used 1010 by some high performance threaded applications. Disabling 1011 this option saves about 7k. 1012 1013config HAVE_PERF_EVENTS 1014 bool 1015 help 1016 See tools/perf/design.txt for details. 1017 1018config PERF_USE_VMALLOC 1019 bool 1020 help 1021 See tools/perf/design.txt for details 1022 1023menu "Kernel Performance Events And Counters" 1024 1025config PERF_EVENTS 1026 bool "Kernel performance events and counters" 1027 default y if (PROFILING || PERF_COUNTERS) 1028 depends on HAVE_PERF_EVENTS 1029 select ANON_INODES 1030 select IRQ_WORK 1031 help 1032 Enable kernel support for various performance events provided 1033 by software and hardware. 1034 1035 Software events are supported either built-in or via the 1036 use of generic tracepoints. 1037 1038 Most modern CPUs support performance events via performance 1039 counter registers. These registers count the number of certain 1040 types of hw events: such as instructions executed, cachemisses 1041 suffered, or branches mis-predicted - without slowing down the 1042 kernel or applications. These registers can also trigger interrupts 1043 when a threshold number of events have passed - and can thus be 1044 used to profile the code that runs on that CPU. 1045 1046 The Linux Performance Event subsystem provides an abstraction of 1047 these software and hardware event capabilities, available via a 1048 system call and used by the "perf" utility in tools/perf/. It 1049 provides per task and per CPU counters, and it provides event 1050 capabilities on top of those. 1051 1052 Say Y if unsure. 1053 1054config PERF_COUNTERS 1055 bool "Kernel performance counters (old config option)" 1056 depends on HAVE_PERF_EVENTS 1057 help 1058 This config has been obsoleted by the PERF_EVENTS 1059 config option - please see that one for details. 1060 1061 It has no effect on the kernel whether you enable 1062 it or not, it is a compatibility placeholder. 1063 1064 Say N if unsure. 1065 1066config DEBUG_PERF_USE_VMALLOC 1067 default n 1068 bool "Debug: use vmalloc to back perf mmap() buffers" 1069 depends on PERF_EVENTS && DEBUG_KERNEL 1070 select PERF_USE_VMALLOC 1071 help 1072 Use vmalloc memory to back perf mmap() buffers. 1073 1074 Mostly useful for debugging the vmalloc code on platforms 1075 that don't require it. 1076 1077 Say N if unsure. 1078 1079endmenu 1080 1081config VM_EVENT_COUNTERS 1082 default y 1083 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED 1084 help 1085 VM event counters are needed for event counts to be shown. 1086 This option allows the disabling of the VM event counters 1087 on EMBEDDED systems. /proc/vmstat will only show page counts 1088 if VM event counters are disabled. 1089 1090config PCI_QUIRKS 1091 default y 1092 bool "Enable PCI quirk workarounds" if EMBEDDED 1093 depends on PCI 1094 help 1095 This enables workarounds for various PCI chipset 1096 bugs/quirks. Disable this only if your target machine is 1097 unaffected by PCI quirks. 1098 1099config SLUB_DEBUG 1100 default y 1101 bool "Enable SLUB debugging support" if EMBEDDED 1102 depends on SLUB && SYSFS 1103 help 1104 SLUB has extensive debug support features. Disabling these can 1105 result in significant savings in code size. This also disables 1106 SLUB sysfs support. /sys/slab will not exist and there will be 1107 no support for cache validation etc. 1108 1109config COMPAT_BRK 1110 bool "Disable heap randomization" 1111 default y 1112 help 1113 Randomizing heap placement makes heap exploits harder, but it 1114 also breaks ancient binaries (including anything libc5 based). 1115 This option changes the bootup default to heap randomization 1116 disabled, and can be overridden at runtime by setting 1117 /proc/sys/kernel/randomize_va_space to 2. 1118 1119 On non-ancient distros (post-2000 ones) N is usually a safe choice. 1120 1121choice 1122 prompt "Choose SLAB allocator" 1123 default SLUB 1124 help 1125 This option allows to select a slab allocator. 1126 1127config SLAB 1128 bool "SLAB" 1129 help 1130 The regular slab allocator that is established and known to work 1131 well in all environments. It organizes cache hot objects in 1132 per cpu and per node queues. 1133 1134config SLUB 1135 bool "SLUB (Unqueued Allocator)" 1136 help 1137 SLUB is a slab allocator that minimizes cache line usage 1138 instead of managing queues of cached objects (SLAB approach). 1139 Per cpu caching is realized using slabs of objects instead 1140 of queues of objects. SLUB can use memory efficiently 1141 and has enhanced diagnostics. SLUB is the default choice for 1142 a slab allocator. 1143 1144config SLOB 1145 depends on EMBEDDED 1146 bool "SLOB (Simple Allocator)" 1147 help 1148 SLOB replaces the stock allocator with a drastically simpler 1149 allocator. SLOB is generally more space efficient but 1150 does not perform as well on large systems. 1151 1152endchoice 1153 1154config MMAP_ALLOW_UNINITIALIZED 1155 bool "Allow mmapped anonymous memory to be uninitialized" 1156 depends on EMBEDDED && !MMU 1157 default n 1158 help 1159 Normally, and according to the Linux spec, anonymous memory obtained 1160 from mmap() has it's contents cleared before it is passed to 1161 userspace. Enabling this config option allows you to request that 1162 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 1163 providing a huge performance boost. If this option is not enabled, 1164 then the flag will be ignored. 1165 1166 This is taken advantage of by uClibc's malloc(), and also by 1167 ELF-FDPIC binfmt's brk and stack allocator. 1168 1169 Because of the obvious security issues, this option should only be 1170 enabled on embedded devices where you control what is run in 1171 userspace. Since that isn't generally a problem on no-MMU systems, 1172 it is normally safe to say Y here. 1173 1174 See Documentation/nommu-mmap.txt for more information. 1175 1176config PROFILING 1177 bool "Profiling support" 1178 help 1179 Say Y here to enable the extended profiling support mechanisms used 1180 by profilers such as OProfile. 1181 1182# 1183# Place an empty function call at each tracepoint site. Can be 1184# dynamically changed for a probe function. 1185# 1186config TRACEPOINTS 1187 bool 1188 1189source "arch/Kconfig" 1190 1191endmenu # General setup 1192 1193config HAVE_GENERIC_DMA_COHERENT 1194 bool 1195 default n 1196 1197config SLABINFO 1198 bool 1199 depends on PROC_FS 1200 depends on SLAB || SLUB_DEBUG 1201 default y 1202 1203config RT_MUTEXES 1204 boolean 1205 1206config BASE_SMALL 1207 int 1208 default 0 if BASE_FULL 1209 default 1 if !BASE_FULL 1210 1211menuconfig MODULES 1212 bool "Enable loadable module support" 1213 help 1214 Kernel modules are small pieces of compiled code which can 1215 be inserted in the running kernel, rather than being 1216 permanently built into the kernel. You use the "modprobe" 1217 tool to add (and sometimes remove) them. If you say Y here, 1218 many parts of the kernel can be built as modules (by 1219 answering M instead of Y where indicated): this is most 1220 useful for infrequently used options which are not required 1221 for booting. For more information, see the man pages for 1222 modprobe, lsmod, modinfo, insmod and rmmod. 1223 1224 If you say Y here, you will need to run "make 1225 modules_install" to put the modules under /lib/modules/ 1226 where modprobe can find them (you may need to be root to do 1227 this). 1228 1229 If unsure, say Y. 1230 1231if MODULES 1232 1233config MODULE_FORCE_LOAD 1234 bool "Forced module loading" 1235 default n 1236 help 1237 Allow loading of modules without version information (ie. modprobe 1238 --force). Forced module loading sets the 'F' (forced) taint flag and 1239 is usually a really bad idea. 1240 1241config MODULE_UNLOAD 1242 bool "Module unloading" 1243 help 1244 Without this option you will not be able to unload any 1245 modules (note that some modules may not be unloadable 1246 anyway), which makes your kernel smaller, faster 1247 and simpler. If unsure, say Y. 1248 1249config MODULE_FORCE_UNLOAD 1250 bool "Forced module unloading" 1251 depends on MODULE_UNLOAD && EXPERIMENTAL 1252 help 1253 This option allows you to force a module to unload, even if the 1254 kernel believes it is unsafe: the kernel will remove the module 1255 without waiting for anyone to stop using it (using the -f option to 1256 rmmod). This is mainly for kernel developers and desperate users. 1257 If unsure, say N. 1258 1259config MODVERSIONS 1260 bool "Module versioning support" 1261 help 1262 Usually, you have to use modules compiled with your kernel. 1263 Saying Y here makes it sometimes possible to use modules 1264 compiled for different kernels, by adding enough information 1265 to the modules to (hopefully) spot any changes which would 1266 make them incompatible with the kernel you are running. If 1267 unsure, say N. 1268 1269config MODULE_SRCVERSION_ALL 1270 bool "Source checksum for all modules" 1271 help 1272 Modules which contain a MODULE_VERSION get an extra "srcversion" 1273 field inserted into their modinfo section, which contains a 1274 sum of the source files which made it. This helps maintainers 1275 see exactly which source was used to build a module (since 1276 others sometimes change the module source without updating 1277 the version). With this option, such a "srcversion" field 1278 will be created for all modules. If unsure, say N. 1279 1280endif # MODULES 1281 1282config INIT_ALL_POSSIBLE 1283 bool 1284 help 1285 Back when each arch used to define their own cpu_online_map and 1286 cpu_possible_map, some of them chose to initialize cpu_possible_map 1287 with all 1s, and others with all 0s. When they were centralised, 1288 it was better to provide this option than to break all the archs 1289 and have several arch maintainers pursuing me down dark alleys. 1290 1291config STOP_MACHINE 1292 bool 1293 default y 1294 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU 1295 help 1296 Need stop_machine() primitive. 1297 1298source "block/Kconfig" 1299 1300config PREEMPT_NOTIFIERS 1301 bool 1302 1303config PADATA 1304 depends on SMP 1305 bool 1306 1307source "kernel/Kconfig.locks" 1308