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Based on kernel version 2.6.34. Page generated on 2010-05-31 16:02 EST.
1 ------------------------------------------------------------------------------ 2 T H E /proc F I L E S Y S T E M 3 ------------------------------------------------------------------------------ 4 /proc/sys Terrehon Bowden <terrehon[AT]pacbell[DOT]net> October 7 1999 5 Bodo Bauer <bb[AT]ricochet[DOT]net> 6 7 2.4.x update Jorge Nerin <comandante[AT]zaralinux[DOT]com> November 14 2000 8 move /proc/sys Shen Feng <shen[AT]cn.fujitsu[DOT]com> April 1 2009 9 ------------------------------------------------------------------------------ 10 Version 1.3 Kernel version 2.2.12 11 Kernel version 2.4.0-test11-pre4 12 ------------------------------------------------------------------------------ 13 fixes/update part 1.1 Stefani Seibold <stefani[AT]seibold[DOT]net> June 9 2009 14 15 Table of Contents 16 ----------------- 17 18 0 Preface 19 0.1 Introduction/Credits 20 0.2 Legal Stuff 21 22 1 Collecting System Information 23 1.1 Process-Specific Subdirectories 24 1.2 Kernel data 25 1.3 IDE devices in /proc/ide 26 1.4 Networking info in /proc/net 27 1.5 SCSI info 28 1.6 Parallel port info in /proc/parport 29 1.7 TTY info in /proc/tty 30 1.8 Miscellaneous kernel statistics in /proc/stat 31 1.9 Ext4 file system parameters 32 33 2 Modifying System Parameters 34 35 3 Per-Process Parameters 36 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score 37 3.2 /proc/<pid>/oom_score - Display current oom-killer score 38 3.3 /proc/<pid>/io - Display the IO accounting fields 39 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 40 3.5 /proc/<pid>/mountinfo - Information about mounts 41 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 42 43 44 ------------------------------------------------------------------------------ 45 Preface 46 ------------------------------------------------------------------------------ 47 48 0.1 Introduction/Credits 49 ------------------------ 50 51 This documentation is part of a soon (or so we hope) to be released book on 52 the SuSE Linux distribution. As there is no complete documentation for the 53 /proc file system and we've used many freely available sources to write these 54 chapters, it seems only fair to give the work back to the Linux community. 55 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm 56 afraid it's still far from complete, but we hope it will be useful. As far as 57 we know, it is the first 'all-in-one' document about the /proc file system. It 58 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, 59 SPARC, AXP, etc., features, you probably won't find what you are looking for. 60 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But 61 additions and patches are welcome and will be added to this document if you 62 mail them to Bodo. 63 64 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of 65 other people for help compiling this documentation. We'd also like to extend a 66 special thank you to Andi Kleen for documentation, which we relied on heavily 67 to create this document, as well as the additional information he provided. 68 Thanks to everybody else who contributed source or docs to the Linux kernel 69 and helped create a great piece of software... :) 70 71 If you have any comments, corrections or additions, please don't hesitate to 72 contact Bodo Bauer at bb[AT]ricochet.net[DOT] We'll be happy to add them to this 73 document. 74 75 The latest version of this document is available online at 76 http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version. 77 78 If the above direction does not works for you, ypu could try the kernel 79 mailing list at linux-kernel[AT]vger.kernel[DOT]org and/or try to reach me at 80 comandante[AT]zaralinux.com[DOT] 81 82 0.2 Legal Stuff 83 --------------- 84 85 We don't guarantee the correctness of this document, and if you come to us 86 complaining about how you screwed up your system because of incorrect 87 documentation, we won't feel responsible... 88 89 ------------------------------------------------------------------------------ 90 CHAPTER 1: COLLECTING SYSTEM INFORMATION 91 ------------------------------------------------------------------------------ 92 93 ------------------------------------------------------------------------------ 94 In This Chapter 95 ------------------------------------------------------------------------------ 96 * Investigating the properties of the pseudo file system /proc and its 97 ability to provide information on the running Linux system 98 * Examining /proc's structure 99 * Uncovering various information about the kernel and the processes running 100 on the system 101 ------------------------------------------------------------------------------ 102 103 104 The proc file system acts as an interface to internal data structures in the 105 kernel. It can be used to obtain information about the system and to change 106 certain kernel parameters at runtime (sysctl). 107 108 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we 109 show you how you can use /proc/sys to change settings. 110 111 1.1 Process-Specific Subdirectories 112 ----------------------------------- 113 114 The directory /proc contains (among other things) one subdirectory for each 115 process running on the system, which is named after the process ID (PID). 116 117 The link self points to the process reading the file system. Each process 118 subdirectory has the entries listed in Table 1-1. 119 120 121 Table 1-1: Process specific entries in /proc 122 .............................................................................. 123 File Content 124 clear_refs Clears page referenced bits shown in smaps output 125 cmdline Command line arguments 126 cpu Current and last cpu in which it was executed (2.4)(smp) 127 cwd Link to the current working directory 128 environ Values of environment variables 129 exe Link to the executable of this process 130 fd Directory, which contains all file descriptors 131 maps Memory maps to executables and library files (2.4) 132 mem Memory held by this process 133 root Link to the root directory of this process 134 stat Process status 135 statm Process memory status information 136 status Process status in human readable form 137 wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan 138 stack Report full stack trace, enable via CONFIG_STACKTRACE 139 smaps a extension based on maps, showing the memory consumption of 140 each mapping 141 .............................................................................. 142 143 For example, to get the status information of a process, all you have to do is 144 read the file /proc/PID/status: 145 146 >cat /proc/self/status 147 Name: cat 148 State: R (running) 149 Tgid: 5452 150 Pid: 5452 151 PPid: 743 152 TracerPid: 0 (2.4) 153 Uid: 501 501 501 501 154 Gid: 100 100 100 100 155 FDSize: 256 156 Groups: 100 14 16 157 VmPeak: 5004 kB 158 VmSize: 5004 kB 159 VmLck: 0 kB 160 VmHWM: 476 kB 161 VmRSS: 476 kB 162 VmData: 156 kB 163 VmStk: 88 kB 164 VmExe: 68 kB 165 VmLib: 1412 kB 166 VmPTE: 20 kb 167 VmSwap: 0 kB 168 Threads: 1 169 SigQ: 0/28578 170 SigPnd: 0000000000000000 171 ShdPnd: 0000000000000000 172 SigBlk: 0000000000000000 173 SigIgn: 0000000000000000 174 SigCgt: 0000000000000000 175 CapInh: 00000000fffffeff 176 CapPrm: 0000000000000000 177 CapEff: 0000000000000000 178 CapBnd: ffffffffffffffff 179 voluntary_ctxt_switches: 0 180 nonvoluntary_ctxt_switches: 1 181 182 This shows you nearly the same information you would get if you viewed it with 183 the ps command. In fact, ps uses the proc file system to obtain its 184 information. But you get a more detailed view of the process by reading the 185 file /proc/PID/status. It fields are described in table 1-2. 186 187 The statm file contains more detailed information about the process 188 memory usage. Its seven fields are explained in Table 1-3. The stat file 189 contains details information about the process itself. Its fields are 190 explained in Table 1-4. 191 192 (for SMP CONFIG users) 193 For making accounting scalable, RSS related information are handled in 194 asynchronous manner and the vaule may not be very precise. To see a precise 195 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table. 196 It's slow but very precise. 197 198 Table 1-2: Contents of the status files (as of 2.6.30-rc7) 199 .............................................................................. 200 Field Content 201 Name filename of the executable 202 State state (R is running, S is sleeping, D is sleeping 203 in an uninterruptible wait, Z is zombie, 204 T is traced or stopped) 205 Tgid thread group ID 206 Pid process id 207 PPid process id of the parent process 208 TracerPid PID of process tracing this process (0 if not) 209 Uid Real, effective, saved set, and file system UIDs 210 Gid Real, effective, saved set, and file system GIDs 211 FDSize number of file descriptor slots currently allocated 212 Groups supplementary group list 213 VmPeak peak virtual memory size 214 VmSize total program size 215 VmLck locked memory size 216 VmHWM peak resident set size ("high water mark") 217 VmRSS size of memory portions 218 VmData size of data, stack, and text segments 219 VmStk size of data, stack, and text segments 220 VmExe size of text segment 221 VmLib size of shared library code 222 VmPTE size of page table entries 223 VmSwap size of swap usage (the number of referred swapents) 224 Threads number of threads 225 SigQ number of signals queued/max. number for queue 226 SigPnd bitmap of pending signals for the thread 227 ShdPnd bitmap of shared pending signals for the process 228 SigBlk bitmap of blocked signals 229 SigIgn bitmap of ignored signals 230 SigCgt bitmap of catched signals 231 CapInh bitmap of inheritable capabilities 232 CapPrm bitmap of permitted capabilities 233 CapEff bitmap of effective capabilities 234 CapBnd bitmap of capabilities bounding set 235 Cpus_allowed mask of CPUs on which this process may run 236 Cpus_allowed_list Same as previous, but in "list format" 237 Mems_allowed mask of memory nodes allowed to this process 238 Mems_allowed_list Same as previous, but in "list format" 239 voluntary_ctxt_switches number of voluntary context switches 240 nonvoluntary_ctxt_switches number of non voluntary context switches 241 .............................................................................. 242 243 Table 1-3: Contents of the statm files (as of 2.6.8-rc3) 244 .............................................................................. 245 Field Content 246 size total program size (pages) (same as VmSize in status) 247 resident size of memory portions (pages) (same as VmRSS in status) 248 shared number of pages that are shared (i.e. backed by a file) 249 trs number of pages that are 'code' (not including libs; broken, 250 includes data segment) 251 lrs number of pages of library (always 0 on 2.6) 252 drs number of pages of data/stack (including libs; broken, 253 includes library text) 254 dt number of dirty pages (always 0 on 2.6) 255 .............................................................................. 256 257 258 Table 1-4: Contents of the stat files (as of 2.6.30-rc7) 259 .............................................................................. 260 Field Content 261 pid process id 262 tcomm filename of the executable 263 state state (R is running, S is sleeping, D is sleeping in an 264 uninterruptible wait, Z is zombie, T is traced or stopped) 265 ppid process id of the parent process 266 pgrp pgrp of the process 267 sid session id 268 tty_nr tty the process uses 269 tty_pgrp pgrp of the tty 270 flags task flags 271 min_flt number of minor faults 272 cmin_flt number of minor faults with child's 273 maj_flt number of major faults 274 cmaj_flt number of major faults with child's 275 utime user mode jiffies 276 stime kernel mode jiffies 277 cutime user mode jiffies with child's 278 cstime kernel mode jiffies with child's 279 priority priority level 280 nice nice level 281 num_threads number of threads 282 it_real_value (obsolete, always 0) 283 start_time time the process started after system boot 284 vsize virtual memory size 285 rss resident set memory size 286 rsslim current limit in bytes on the rss 287 start_code address above which program text can run 288 end_code address below which program text can run 289 start_stack address of the start of the stack 290 esp current value of ESP 291 eip current value of EIP 292 pending bitmap of pending signals 293 blocked bitmap of blocked signals 294 sigign bitmap of ignored signals 295 sigcatch bitmap of catched signals 296 wchan address where process went to sleep 297 0 (place holder) 298 0 (place holder) 299 exit_signal signal to send to parent thread on exit 300 task_cpu which CPU the task is scheduled on 301 rt_priority realtime priority 302 policy scheduling policy (man sched_setscheduler) 303 blkio_ticks time spent waiting for block IO 304 gtime guest time of the task in jiffies 305 cgtime guest time of the task children in jiffies 306 .............................................................................. 307 308 The /proc/PID/map file containing the currently mapped memory regions and 309 their access permissions. 310 311 The format is: 312 313 address perms offset dev inode pathname 314 315 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test 316 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test 317 0804a000-0806b000 rw-p 00000000 00:00 0 [heap] 318 a7cb1000-a7cb2000 ---p 00000000 00:00 0 319 a7cb2000-a7eb2000 rw-p 00000000 00:00 0 320 a7eb2000-a7eb3000 ---p 00000000 00:00 0 321 a7eb3000-a7ed5000 rw-p 00000000 00:00 0 322 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6 323 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6 324 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6 325 a800b000-a800e000 rw-p 00000000 00:00 0 326 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0 327 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0 328 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0 329 a8024000-a8027000 rw-p 00000000 00:00 0 330 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2 331 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2 332 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2 333 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack] 334 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso] 335 336 where "address" is the address space in the process that it occupies, "perms" 337 is a set of permissions: 338 339 r = read 340 w = write 341 x = execute 342 s = shared 343 p = private (copy on write) 344 345 "offset" is the offset into the mapping, "dev" is the device (major:minor), and 346 "inode" is the inode on that device. 0 indicates that no inode is associated 347 with the memory region, as the case would be with BSS (uninitialized data). 348 The "pathname" shows the name associated file for this mapping. If the mapping 349 is not associated with a file: 350 351 [heap] = the heap of the program 352 [stack] = the stack of the main process 353 [vdso] = the "virtual dynamic shared object", 354 the kernel system call handler 355 356 or if empty, the mapping is anonymous. 357 358 359 The /proc/PID/smaps is an extension based on maps, showing the memory 360 consumption for each of the process's mappings. For each of mappings there 361 is a series of lines such as the following: 362 363 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash 364 Size: 1084 kB 365 Rss: 892 kB 366 Pss: 374 kB 367 Shared_Clean: 892 kB 368 Shared_Dirty: 0 kB 369 Private_Clean: 0 kB 370 Private_Dirty: 0 kB 371 Referenced: 892 kB 372 Swap: 0 kB 373 KernelPageSize: 4 kB 374 MMUPageSize: 4 kB 375 376 The first of these lines shows the same information as is displayed for the 377 mapping in /proc/PID/maps. The remaining lines show the size of the mapping, 378 the amount of the mapping that is currently resident in RAM, the "proportional 379 set sizeâ (divide each shared page by the number of processes sharing it), the 380 number of clean and dirty shared pages in the mapping, and the number of clean 381 and dirty private pages in the mapping. The "Referenced" indicates the amount 382 of memory currently marked as referenced or accessed. 383 384 This file is only present if the CONFIG_MMU kernel configuration option is 385 enabled. 386 387 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG 388 bits on both physical and virtual pages associated with a process. 389 To clear the bits for all the pages associated with the process 390 > echo 1 > /proc/PID/clear_refs 391 392 To clear the bits for the anonymous pages associated with the process 393 > echo 2 > /proc/PID/clear_refs 394 395 To clear the bits for the file mapped pages associated with the process 396 > echo 3 > /proc/PID/clear_refs 397 Any other value written to /proc/PID/clear_refs will have no effect. 398 399 400 1.2 Kernel data 401 --------------- 402 403 Similar to the process entries, the kernel data files give information about 404 the running kernel. The files used to obtain this information are contained in 405 /proc and are listed in Table 1-5. Not all of these will be present in your 406 system. It depends on the kernel configuration and the loaded modules, which 407 files are there, and which are missing. 408 409 Table 1-5: Kernel info in /proc 410 .............................................................................. 411 File Content 412 apm Advanced power management info 413 buddyinfo Kernel memory allocator information (see text) (2.5) 414 bus Directory containing bus specific information 415 cmdline Kernel command line 416 cpuinfo Info about the CPU 417 devices Available devices (block and character) 418 dma Used DMS channels 419 filesystems Supported filesystems 420 driver Various drivers grouped here, currently rtc (2.4) 421 execdomains Execdomains, related to security (2.4) 422 fb Frame Buffer devices (2.4) 423 fs File system parameters, currently nfs/exports (2.4) 424 ide Directory containing info about the IDE subsystem 425 interrupts Interrupt usage 426 iomem Memory map (2.4) 427 ioports I/O port usage 428 irq Masks for irq to cpu affinity (2.4)(smp?) 429 isapnp ISA PnP (Plug&Play) Info (2.4) 430 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) 431 kmsg Kernel messages 432 ksyms Kernel symbol table 433 loadavg Load average of last 1, 5 & 15 minutes 434 locks Kernel locks 435 meminfo Memory info 436 misc Miscellaneous 437 modules List of loaded modules 438 mounts Mounted filesystems 439 net Networking info (see text) 440 pagetypeinfo Additional page allocator information (see text) (2.5) 441 partitions Table of partitions known to the system 442 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, 443 decoupled by lspci (2.4) 444 rtc Real time clock 445 scsi SCSI info (see text) 446 slabinfo Slab pool info 447 softirqs softirq usage 448 stat Overall statistics 449 swaps Swap space utilization 450 sys See chapter 2 451 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) 452 tty Info of tty drivers 453 uptime System uptime 454 version Kernel version 455 video bttv info of video resources (2.4) 456 vmallocinfo Show vmalloced areas 457 .............................................................................. 458 459 You can, for example, check which interrupts are currently in use and what 460 they are used for by looking in the file /proc/interrupts: 461 462 > cat /proc/interrupts 463 CPU0 464 0: 8728810 XT-PIC timer 465 1: 895 XT-PIC keyboard 466 2: 0 XT-PIC cascade 467 3: 531695 XT-PIC aha152x 468 4: 2014133 XT-PIC serial 469 5: 44401 XT-PIC pcnet_cs 470 8: 2 XT-PIC rtc 471 11: 8 XT-PIC i82365 472 12: 182918 XT-PIC PS/2 Mouse 473 13: 1 XT-PIC fpu 474 14: 1232265 XT-PIC ide0 475 15: 7 XT-PIC ide1 476 NMI: 0 477 478 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the 479 output of a SMP machine): 480 481 > cat /proc/interrupts 482 483 CPU0 CPU1 484 0: 1243498 1214548 IO-APIC-edge timer 485 1: 8949 8958 IO-APIC-edge keyboard 486 2: 0 0 XT-PIC cascade 487 5: 11286 10161 IO-APIC-edge soundblaster 488 8: 1 0 IO-APIC-edge rtc 489 9: 27422 27407 IO-APIC-edge 3c503 490 12: 113645 113873 IO-APIC-edge PS/2 Mouse 491 13: 0 0 XT-PIC fpu 492 14: 22491 24012 IO-APIC-edge ide0 493 15: 2183 2415 IO-APIC-edge ide1 494 17: 30564 30414 IO-APIC-level eth0 495 18: 177 164 IO-APIC-level bttv 496 NMI: 2457961 2457959 497 LOC: 2457882 2457881 498 ERR: 2155 499 500 NMI is incremented in this case because every timer interrupt generates a NMI 501 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. 502 503 LOC is the local interrupt counter of the internal APIC of every CPU. 504 505 ERR is incremented in the case of errors in the IO-APIC bus (the bus that 506 connects the CPUs in a SMP system. This means that an error has been detected, 507 the IO-APIC automatically retry the transmission, so it should not be a big 508 problem, but you should read the SMP-FAQ. 509 510 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for 511 /proc/interrupts to display every IRQ vector in use by the system, not 512 just those considered 'most important'. The new vectors are: 513 514 THR -- interrupt raised when a machine check threshold counter 515 (typically counting ECC corrected errors of memory or cache) exceeds 516 a configurable threshold. Only available on some systems. 517 518 TRM -- a thermal event interrupt occurs when a temperature threshold 519 has been exceeded for the CPU. This interrupt may also be generated 520 when the temperature drops back to normal. 521 522 SPU -- a spurious interrupt is some interrupt that was raised then lowered 523 by some IO device before it could be fully processed by the APIC. Hence 524 the APIC sees the interrupt but does not know what device it came from. 525 For this case the APIC will generate the interrupt with a IRQ vector 526 of 0xff. This might also be generated by chipset bugs. 527 528 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are 529 sent from one CPU to another per the needs of the OS. Typically, 530 their statistics are used by kernel developers and interested users to 531 determine the occurrence of interrupts of the given type. 532 533 The above IRQ vectors are displayed only when relevent. For example, 534 the threshold vector does not exist on x86_64 platforms. Others are 535 suppressed when the system is a uniprocessor. As of this writing, only 536 i386 and x86_64 platforms support the new IRQ vector displays. 537 538 Of some interest is the introduction of the /proc/irq directory to 2.4. 539 It could be used to set IRQ to CPU affinity, this means that you can "hook" an 540 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the 541 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and 542 prof_cpu_mask. 543 544 For example 545 > ls /proc/irq/ 546 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask 547 1 11 13 15 17 19 3 5 7 9 default_smp_affinity 548 > ls /proc/irq/0/ 549 smp_affinity 550 551 smp_affinity is a bitmask, in which you can specify which CPUs can handle the 552 IRQ, you can set it by doing: 553 554 > echo 1 > /proc/irq/10/smp_affinity 555 556 This means that only the first CPU will handle the IRQ, but you can also echo 557 5 which means that only the first and fourth CPU can handle the IRQ. 558 559 The contents of each smp_affinity file is the same by default: 560 561 > cat /proc/irq/0/smp_affinity 562 ffffffff 563 564 The default_smp_affinity mask applies to all non-active IRQs, which are the 565 IRQs which have not yet been allocated/activated, and hence which lack a 566 /proc/irq/[0-9]* directory. 567 568 prof_cpu_mask specifies which CPUs are to be profiled by the system wide 569 profiler. Default value is ffffffff (all cpus). 570 571 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin 572 between all the CPUs which are allowed to handle it. As usual the kernel has 573 more info than you and does a better job than you, so the defaults are the 574 best choice for almost everyone. 575 576 There are three more important subdirectories in /proc: net, scsi, and sys. 577 The general rule is that the contents, or even the existence of these 578 directories, depend on your kernel configuration. If SCSI is not enabled, the 579 directory scsi may not exist. The same is true with the net, which is there 580 only when networking support is present in the running kernel. 581 582 The slabinfo file gives information about memory usage at the slab level. 583 Linux uses slab pools for memory management above page level in version 2.2. 584 Commonly used objects have their own slab pool (such as network buffers, 585 directory cache, and so on). 586 587 .............................................................................. 588 589 > cat /proc/buddyinfo 590 591 Node 0, zone DMA 0 4 5 4 4 3 ... 592 Node 0, zone Normal 1 0 0 1 101 8 ... 593 Node 0, zone HighMem 2 0 0 1 1 0 ... 594 595 External fragmentation is a problem under some workloads, and buddyinfo is a 596 useful tool for helping diagnose these problems. Buddyinfo will give you a 597 clue as to how big an area you can safely allocate, or why a previous 598 allocation failed. 599 600 Each column represents the number of pages of a certain order which are 601 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in 602 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE 603 available in ZONE_NORMAL, etc... 604 605 More information relevant to external fragmentation can be found in 606 pagetypeinfo. 607 608 > cat /proc/pagetypeinfo 609 Page block order: 9 610 Pages per block: 512 611 612 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10 613 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0 614 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0 615 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2 616 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0 617 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0 618 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9 619 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0 620 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452 621 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0 622 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0 623 624 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate 625 Node 0, zone DMA 2 0 5 1 0 626 Node 0, zone DMA32 41 6 967 2 0 627 628 Fragmentation avoidance in the kernel works by grouping pages of different 629 migrate types into the same contiguous regions of memory called page blocks. 630 A page block is typically the size of the default hugepage size e.g. 2MB on 631 X86-64. By keeping pages grouped based on their ability to move, the kernel 632 can reclaim pages within a page block to satisfy a high-order allocation. 633 634 The pagetypinfo begins with information on the size of a page block. It 635 then gives the same type of information as buddyinfo except broken down 636 by migrate-type and finishes with details on how many page blocks of each 637 type exist. 638 639 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm 640 from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can 641 make an estimate of the likely number of huge pages that can be allocated 642 at a given point in time. All the "Movable" blocks should be allocatable 643 unless memory has been mlock()'d. Some of the Reclaimable blocks should 644 also be allocatable although a lot of filesystem metadata may have to be 645 reclaimed to achieve this. 646 647 .............................................................................. 648 649 meminfo: 650 651 Provides information about distribution and utilization of memory. This 652 varies by architecture and compile options. The following is from a 653 16GB PIII, which has highmem enabled. You may not have all of these fields. 654 655 > cat /proc/meminfo 656 657 658 MemTotal: 16344972 kB 659 MemFree: 13634064 kB 660 Buffers: 3656 kB 661 Cached: 1195708 kB 662 SwapCached: 0 kB 663 Active: 891636 kB 664 Inactive: 1077224 kB 665 HighTotal: 15597528 kB 666 HighFree: 13629632 kB 667 LowTotal: 747444 kB 668 LowFree: 4432 kB 669 SwapTotal: 0 kB 670 SwapFree: 0 kB 671 Dirty: 968 kB 672 Writeback: 0 kB 673 AnonPages: 861800 kB 674 Mapped: 280372 kB 675 Slab: 284364 kB 676 SReclaimable: 159856 kB 677 SUnreclaim: 124508 kB 678 PageTables: 24448 kB 679 NFS_Unstable: 0 kB 680 Bounce: 0 kB 681 WritebackTmp: 0 kB 682 CommitLimit: 7669796 kB 683 Committed_AS: 100056 kB 684 VmallocTotal: 112216 kB 685 VmallocUsed: 428 kB 686 VmallocChunk: 111088 kB 687 688 MemTotal: Total usable ram (i.e. physical ram minus a few reserved 689 bits and the kernel binary code) 690 MemFree: The sum of LowFree+HighFree 691 Buffers: Relatively temporary storage for raw disk blocks 692 shouldn't get tremendously large (20MB or so) 693 Cached: in-memory cache for files read from the disk (the 694 pagecache). Doesn't include SwapCached 695 SwapCached: Memory that once was swapped out, is swapped back in but 696 still also is in the swapfile (if memory is needed it 697 doesn't need to be swapped out AGAIN because it is already 698 in the swapfile. This saves I/O) 699 Active: Memory that has been used more recently and usually not 700 reclaimed unless absolutely necessary. 701 Inactive: Memory which has been less recently used. It is more 702 eligible to be reclaimed for other purposes 703 HighTotal: 704 HighFree: Highmem is all memory above ~860MB of physical memory 705 Highmem areas are for use by userspace programs, or 706 for the pagecache. The kernel must use tricks to access 707 this memory, making it slower to access than lowmem. 708 LowTotal: 709 LowFree: Lowmem is memory which can be used for everything that 710 highmem can be used for, but it is also available for the 711 kernel's use for its own data structures. Among many 712 other things, it is where everything from the Slab is 713 allocated. Bad things happen when you're out of lowmem. 714 SwapTotal: total amount of swap space available 715 SwapFree: Memory which has been evicted from RAM, and is temporarily 716 on the disk 717 Dirty: Memory which is waiting to get written back to the disk 718 Writeback: Memory which is actively being written back to the disk 719 AnonPages: Non-file backed pages mapped into userspace page tables 720 Mapped: files which have been mmaped, such as libraries 721 Slab: in-kernel data structures cache 722 SReclaimable: Part of Slab, that might be reclaimed, such as caches 723 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure 724 PageTables: amount of memory dedicated to the lowest level of page 725 tables. 726 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable 727 storage 728 Bounce: Memory used for block device "bounce buffers" 729 WritebackTmp: Memory used by FUSE for temporary writeback buffers 730 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), 731 this is the total amount of memory currently available to 732 be allocated on the system. This limit is only adhered to 733 if strict overcommit accounting is enabled (mode 2 in 734 'vm.overcommit_memory'). 735 The CommitLimit is calculated with the following formula: 736 CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap 737 For example, on a system with 1G of physical RAM and 7G 738 of swap with a `vm.overcommit_ratio` of 30 it would 739 yield a CommitLimit of 7.3G. 740 For more details, see the memory overcommit documentation 741 in vm/overcommit-accounting. 742 Committed_AS: The amount of memory presently allocated on the system. 743 The committed memory is a sum of all of the memory which 744 has been allocated by processes, even if it has not been 745 "used" by them as of yet. A process which malloc()'s 1G 746 of memory, but only touches 300M of it will only show up 747 as using 300M of memory even if it has the address space 748 allocated for the entire 1G. This 1G is memory which has 749 been "committed" to by the VM and can be used at any time 750 by the allocating application. With strict overcommit 751 enabled on the system (mode 2 in 'vm.overcommit_memory'), 752 allocations which would exceed the CommitLimit (detailed 753 above) will not be permitted. This is useful if one needs 754 to guarantee that processes will not fail due to lack of 755 memory once that memory has been successfully allocated. 756 VmallocTotal: total size of vmalloc memory area 757 VmallocUsed: amount of vmalloc area which is used 758 VmallocChunk: largest contiguous block of vmalloc area which is free 759 760 .............................................................................. 761 762 vmallocinfo: 763 764 Provides information about vmalloced/vmaped areas. One line per area, 765 containing the virtual address range of the area, size in bytes, 766 caller information of the creator, and optional information depending 767 on the kind of area : 768 769 pages=nr number of pages 770 phys=addr if a physical address was specified 771 ioremap I/O mapping (ioremap() and friends) 772 vmalloc vmalloc() area 773 vmap vmap()ed pages 774 user VM_USERMAP area 775 vpages buffer for pages pointers was vmalloced (huge area) 776 N<node>=nr (Only on NUMA kernels) 777 Number of pages allocated on memory node <node> 778 779 > cat /proc/vmallocinfo 780 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... 781 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 782 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... 783 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 784 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... 785 phys=7fee8000 ioremap 786 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... 787 phys=7fee7000 ioremap 788 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 789 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... 790 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 791 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... 792 pages=2 vmalloc N1=2 793 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... 794 /0x130 [x_tables] pages=4 vmalloc N0=4 795 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... 796 pages=14 vmalloc N2=14 797 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... 798 pages=4 vmalloc N1=4 799 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... 800 pages=2 vmalloc N1=2 801 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... 802 pages=10 vmalloc N0=10 803 804 .............................................................................. 805 806 softirqs: 807 808 Provides counts of softirq handlers serviced since boot time, for each cpu. 809 810 > cat /proc/softirqs 811 CPU0 CPU1 CPU2 CPU3 812 HI: 0 0 0 0 813 TIMER: 27166 27120 27097 27034 814 NET_TX: 0 0 0 17 815 NET_RX: 42 0 0 39 816 BLOCK: 0 0 107 1121 817 TASKLET: 0 0 0 290 818 SCHED: 27035 26983 26971 26746 819 HRTIMER: 0 0 0 0 820 RCU: 1678 1769 2178 2250 821 822 823 1.3 IDE devices in /proc/ide 824 ---------------------------- 825 826 The subdirectory /proc/ide contains information about all IDE devices of which 827 the kernel is aware. There is one subdirectory for each IDE controller, the 828 file drivers and a link for each IDE device, pointing to the device directory 829 in the controller specific subtree. 830 831 The file drivers contains general information about the drivers used for the 832 IDE devices: 833 834 > cat /proc/ide/drivers 835 ide-cdrom version 4.53 836 ide-disk version 1.08 837 838 More detailed information can be found in the controller specific 839 subdirectories. These are named ide0, ide1 and so on. Each of these 840 directories contains the files shown in table 1-6. 841 842 843 Table 1-6: IDE controller info in /proc/ide/ide? 844 .............................................................................. 845 File Content 846 channel IDE channel (0 or 1) 847 config Configuration (only for PCI/IDE bridge) 848 mate Mate name 849 model Type/Chipset of IDE controller 850 .............................................................................. 851 852 Each device connected to a controller has a separate subdirectory in the 853 controllers directory. The files listed in table 1-7 are contained in these 854 directories. 855 856 857 Table 1-7: IDE device information 858 .............................................................................. 859 File Content 860 cache The cache 861 capacity Capacity of the medium (in 512Byte blocks) 862 driver driver and version 863 geometry physical and logical geometry 864 identify device identify block 865 media media type 866 model device identifier 867 settings device setup 868 smart_thresholds IDE disk management thresholds 869 smart_values IDE disk management values 870 .............................................................................. 871 872 The most interesting file is settings. This file contains a nice overview of 873 the drive parameters: 874 875 # cat /proc/ide/ide0/hda/settings 876 name value min max mode 877 ---- ----- --- --- ---- 878 bios_cyl 526 0 65535 rw 879 bios_head 255 0 255 rw 880 bios_sect 63 0 63 rw 881 breada_readahead 4 0 127 rw 882 bswap 0 0 1 r 883 file_readahead 72 0 2097151 rw 884 io_32bit 0 0 3 rw 885 keepsettings 0 0 1 rw 886 max_kb_per_request 122 1 127 rw 887 multcount 0 0 8 rw 888 nice1 1 0 1 rw 889 nowerr 0 0 1 rw 890 pio_mode write-only 0 255 w 891 slow 0 0 1 rw 892 unmaskirq 0 0 1 rw 893 using_dma 0 0 1 rw 894 895 896 1.4 Networking info in /proc/net 897 -------------------------------- 898 899 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the 900 additional values you get for IP version 6 if you configure the kernel to 901 support this. Table 1-9 lists the files and their meaning. 902 903 904 Table 1-8: IPv6 info in /proc/net 905 .............................................................................. 906 File Content 907 udp6 UDP sockets (IPv6) 908 tcp6 TCP sockets (IPv6) 909 raw6 Raw device statistics (IPv6) 910 igmp6 IP multicast addresses, which this host joined (IPv6) 911 if_inet6 List of IPv6 interface addresses 912 ipv6_route Kernel routing table for IPv6 913 rt6_stats Global IPv6 routing tables statistics 914 sockstat6 Socket statistics (IPv6) 915 snmp6 Snmp data (IPv6) 916 .............................................................................. 917 918 919 Table 1-9: Network info in /proc/net 920 .............................................................................. 921 File Content 922 arp Kernel ARP table 923 dev network devices with statistics 924 dev_mcast the Layer2 multicast groups a device is listening too 925 (interface index, label, number of references, number of bound 926 addresses). 927 dev_stat network device status 928 ip_fwchains Firewall chain linkage 929 ip_fwnames Firewall chain names 930 ip_masq Directory containing the masquerading tables 931 ip_masquerade Major masquerading table 932 netstat Network statistics 933 raw raw device statistics 934 route Kernel routing table 935 rpc Directory containing rpc info 936 rt_cache Routing cache 937 snmp SNMP data 938 sockstat Socket statistics 939 tcp TCP sockets 940 tr_rif Token ring RIF routing table 941 udp UDP sockets 942 unix UNIX domain sockets 943 wireless Wireless interface data (Wavelan etc) 944 igmp IP multicast addresses, which this host joined 945 psched Global packet scheduler parameters. 946 netlink List of PF_NETLINK sockets 947 ip_mr_vifs List of multicast virtual interfaces 948 ip_mr_cache List of multicast routing cache 949 .............................................................................. 950 951 You can use this information to see which network devices are available in 952 your system and how much traffic was routed over those devices: 953 954 > cat /proc/net/dev 955 Inter-|Receive |[... 956 face |bytes packets errs drop fifo frame compressed multicast|[... 957 lo: 908188 5596 0 0 0 0 0 0 [... 958 ppp0:15475140 20721 410 0 0 410 0 0 [... 959 eth0: 614530 7085 0 0 0 0 0 1 [... 960 961 ...] Transmit 962 ...] bytes packets errs drop fifo colls carrier compressed 963 ...] 908188 5596 0 0 0 0 0 0 964 ...] 1375103 17405 0 0 0 0 0 0 965 ...] 1703981 5535 0 0 0 3 0 0 966 967 In addition, each Channel Bond interface has it's own directory. For 968 example, the bond0 device will have a directory called /proc/net/bond0/. 969 It will contain information that is specific to that bond, such as the 970 current slaves of the bond, the link status of the slaves, and how 971 many times the slaves link has failed. 972 973 1.5 SCSI info 974 ------------- 975 976 If you have a SCSI host adapter in your system, you'll find a subdirectory 977 named after the driver for this adapter in /proc/scsi. You'll also see a list 978 of all recognized SCSI devices in /proc/scsi: 979 980 >cat /proc/scsi/scsi 981 Attached devices: 982 Host: scsi0 Channel: 00 Id: 00 Lun: 00 983 Vendor: IBM Model: DGHS09U Rev: 03E0 984 Type: Direct-Access ANSI SCSI revision: 03 985 Host: scsi0 Channel: 00 Id: 06 Lun: 00 986 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 987 Type: CD-ROM ANSI SCSI revision: 02 988 989 990 The directory named after the driver has one file for each adapter found in 991 the system. These files contain information about the controller, including 992 the used IRQ and the IO address range. The amount of information shown is 993 dependent on the adapter you use. The example shows the output for an Adaptec 994 AHA-2940 SCSI adapter: 995 996 > cat /proc/scsi/aic7xxx/0 997 998 Adaptec AIC7xxx driver version: 5.1.19/3.2.4 999 Compile Options: 1000 TCQ Enabled By Default : Disabled 1001 AIC7XXX_PROC_STATS : Disabled 1002 AIC7XXX_RESET_DELAY : 5 1003 Adapter Configuration: 1004 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter 1005 Ultra Wide Controller 1006 PCI MMAPed I/O Base: 0xeb001000 1007 Adapter SEEPROM Config: SEEPROM found and used. 1008 Adaptec SCSI BIOS: Enabled 1009 IRQ: 10 1010 SCBs: Active 0, Max Active 2, 1011 Allocated 15, HW 16, Page 255 1012 Interrupts: 160328 1013 BIOS Control Word: 0x18b6 1014 Adapter Control Word: 0x005b 1015 Extended Translation: Enabled 1016 Disconnect Enable Flags: 0xffff 1017 Ultra Enable Flags: 0x0001 1018 Tag Queue Enable Flags: 0x0000 1019 Ordered Queue Tag Flags: 0x0000 1020 Default Tag Queue Depth: 8 1021 Tagged Queue By Device array for aic7xxx host instance 0: 1022 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} 1023 Actual queue depth per device for aic7xxx host instance 0: 1024 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} 1025 Statistics: 1026 (scsi0:0:0:0) 1027 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 1028 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) 1029 Total transfers 160151 (74577 reads and 85574 writes) 1030 (scsi0:0:6:0) 1031 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 1032 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) 1033 Total transfers 0 (0 reads and 0 writes) 1034 1035 1036 1.6 Parallel port info in /proc/parport 1037 --------------------------------------- 1038 1039 The directory /proc/parport contains information about the parallel ports of 1040 your system. It has one subdirectory for each port, named after the port 1041 number (0,1,2,...). 1042 1043 These directories contain the four files shown in Table 1-10. 1044 1045 1046 Table 1-10: Files in /proc/parport 1047 .............................................................................. 1048 File Content 1049 autoprobe Any IEEE-1284 device ID information that has been acquired. 1050 devices list of the device drivers using that port. A + will appear by the 1051 name of the device currently using the port (it might not appear 1052 against any). 1053 hardware Parallel port's base address, IRQ line and DMA channel. 1054 irq IRQ that parport is using for that port. This is in a separate 1055 file to allow you to alter it by writing a new value in (IRQ 1056 number or none). 1057 .............................................................................. 1058 1059 1.7 TTY info in /proc/tty 1060 ------------------------- 1061 1062 Information about the available and actually used tty's can be found in the 1063 directory /proc/tty.You'll find entries for drivers and line disciplines in 1064 this directory, as shown in Table 1-11. 1065 1066 1067 Table 1-11: Files in /proc/tty 1068 .............................................................................. 1069 File Content 1070 drivers list of drivers and their usage 1071 ldiscs registered line disciplines 1072 driver/serial usage statistic and status of single tty lines 1073 .............................................................................. 1074 1075 To see which tty's are currently in use, you can simply look into the file 1076 /proc/tty/drivers: 1077 1078 > cat /proc/tty/drivers 1079 pty_slave /dev/pts 136 0-255 pty:slave 1080 pty_master /dev/ptm 128 0-255 pty:master 1081 pty_slave /dev/ttyp 3 0-255 pty:slave 1082 pty_master /dev/pty 2 0-255 pty:master 1083 serial /dev/cua 5 64-67 serial:callout 1084 serial /dev/ttyS 4 64-67 serial 1085 /dev/tty0 /dev/tty0 4 0 system:vtmaster 1086 /dev/ptmx /dev/ptmx 5 2 system 1087 /dev/console /dev/console 5 1 system:console 1088 /dev/tty /dev/tty 5 0 system:/dev/tty 1089 unknown /dev/tty 4 1-63 console 1090 1091 1092 1.8 Miscellaneous kernel statistics in /proc/stat 1093 ------------------------------------------------- 1094 1095 Various pieces of information about kernel activity are available in the 1096 /proc/stat file. All of the numbers reported in this file are aggregates 1097 since the system first booted. For a quick look, simply cat the file: 1098 1099 > cat /proc/stat 1100 cpu 2255 34 2290 22625563 6290 127 456 0 0 1101 cpu0 1132 34 1441 11311718 3675 127 438 0 0 1102 cpu1 1123 0 849 11313845 2614 0 18 0 0 1103 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] 1104 ctxt 1990473 1105 btime 1062191376 1106 processes 2915 1107 procs_running 1 1108 procs_blocked 0 1109 softirq 183433 0 21755 12 39 1137 231 21459 2263 1110 1111 The very first "cpu" line aggregates the numbers in all of the other "cpuN" 1112 lines. These numbers identify the amount of time the CPU has spent performing 1113 different kinds of work. Time units are in USER_HZ (typically hundredths of a 1114 second). The meanings of the columns are as follows, from left to right: 1115 1116 - user: normal processes executing in user mode 1117 - nice: niced processes executing in user mode 1118 - system: processes executing in kernel mode 1119 - idle: twiddling thumbs 1120 - iowait: waiting for I/O to complete 1121 - irq: servicing interrupts 1122 - softirq: servicing softirqs 1123 - steal: involuntary wait 1124 - guest: running a normal guest 1125 - guest_nice: running a niced guest 1126 1127 The "intr" line gives counts of interrupts serviced since boot time, for each 1128 of the possible system interrupts. The first column is the total of all 1129 interrupts serviced; each subsequent column is the total for that particular 1130 interrupt. 1131 1132 The "ctxt" line gives the total number of context switches across all CPUs. 1133 1134 The "btime" line gives the time at which the system booted, in seconds since 1135 the Unix epoch. 1136 1137 The "processes" line gives the number of processes and threads created, which 1138 includes (but is not limited to) those created by calls to the fork() and 1139 clone() system calls. 1140 1141 The "procs_running" line gives the total number of threads that are 1142 running or ready to run (i.e., the total number of runnable threads). 1143 1144 The "procs_blocked" line gives the number of processes currently blocked, 1145 waiting for I/O to complete. 1146 1147 The "softirq" line gives counts of softirqs serviced since boot time, for each 1148 of the possible system softirqs. The first column is the total of all 1149 softirqs serviced; each subsequent column is the total for that particular 1150 softirq. 1151 1152 1153 1.9 Ext4 file system parameters 1154 ------------------------------ 1155 1156 Information about mounted ext4 file systems can be found in 1157 /proc/fs/ext4. Each mounted filesystem will have a directory in 1158 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or 1159 /proc/fs/ext4/dm-0). The files in each per-device directory are shown 1160 in Table 1-12, below. 1161 1162 Table 1-12: Files in /proc/fs/ext4/<devname> 1163 .............................................................................. 1164 File Content 1165 mb_groups details of multiblock allocator buddy cache of free blocks 1166 .............................................................................. 1167 1168 1169 ------------------------------------------------------------------------------ 1170 Summary 1171 ------------------------------------------------------------------------------ 1172 The /proc file system serves information about the running system. It not only 1173 allows access to process data but also allows you to request the kernel status 1174 by reading files in the hierarchy. 1175 1176 The directory structure of /proc reflects the types of information and makes 1177 it easy, if not obvious, where to look for specific data. 1178 ------------------------------------------------------------------------------ 1179 1180 ------------------------------------------------------------------------------ 1181 CHAPTER 2: MODIFYING SYSTEM PARAMETERS 1182 ------------------------------------------------------------------------------ 1183 1184 ------------------------------------------------------------------------------ 1185 In This Chapter 1186 ------------------------------------------------------------------------------ 1187 * Modifying kernel parameters by writing into files found in /proc/sys 1188 * Exploring the files which modify certain parameters 1189 * Review of the /proc/sys file tree 1190 ------------------------------------------------------------------------------ 1191 1192 1193 A very interesting part of /proc is the directory /proc/sys. This is not only 1194 a source of information, it also allows you to change parameters within the 1195 kernel. Be very careful when attempting this. You can optimize your system, 1196 but you can also cause it to crash. Never alter kernel parameters on a 1197 production system. Set up a development machine and test to make sure that 1198 everything works the way you want it to. You may have no alternative but to 1199 reboot the machine once an error has been made. 1200 1201 To change a value, simply echo the new value into the file. An example is 1202 given below in the section on the file system data. You need to be root to do 1203 this. You can create your own boot script to perform this every time your 1204 system boots. 1205 1206 The files in /proc/sys can be used to fine tune and monitor miscellaneous and 1207 general things in the operation of the Linux kernel. Since some of the files 1208 can inadvertently disrupt your system, it is advisable to read both 1209 documentation and source before actually making adjustments. In any case, be 1210 very careful when writing to any of these files. The entries in /proc may 1211 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt 1212 review the kernel documentation in the directory /usr/src/linux/Documentation. 1213 This chapter is heavily based on the documentation included in the pre 2.2 1214 kernels, and became part of it in version 2.2.1 of the Linux kernel. 1215 1216 Please see: Documentation/sysctls/ directory for descriptions of these 1217 entries. 1218 1219 ------------------------------------------------------------------------------ 1220 Summary 1221 ------------------------------------------------------------------------------ 1222 Certain aspects of kernel behavior can be modified at runtime, without the 1223 need to recompile the kernel, or even to reboot the system. The files in the 1224 /proc/sys tree can not only be read, but also modified. You can use the echo 1225 command to write value into these files, thereby changing the default settings 1226 of the kernel. 1227 ------------------------------------------------------------------------------ 1228 1229 ------------------------------------------------------------------------------ 1230 CHAPTER 3: PER-PROCESS PARAMETERS 1231 ------------------------------------------------------------------------------ 1232 1233 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score 1234 ------------------------------------------------------ 1235 1236 This file can be used to adjust the score used to select which processes 1237 should be killed in an out-of-memory situation. Giving it a high score will 1238 increase the likelihood of this process being killed by the oom-killer. Valid 1239 values are in the range -16 to +15, plus the special value -17, which disables 1240 oom-killing altogether for this process. 1241 1242 The process to be killed in an out-of-memory situation is selected among all others 1243 based on its badness score. This value equals the original memory size of the process 1244 and is then updated according to its CPU time (utime + stime) and the 1245 run time (uptime - start time). The longer it runs the smaller is the score. 1246 Badness score is divided by the square root of the CPU time and then by 1247 the double square root of the run time. 1248 1249 Swapped out tasks are killed first. Half of each child's memory size is added to 1250 the parent's score if they do not share the same memory. Thus forking servers 1251 are the prime candidates to be killed. Having only one 'hungry' child will make 1252 parent less preferable than the child. 1253 1254 /proc/<pid>/oom_score shows process' current badness score. 1255 1256 The following heuristics are then applied: 1257 * if the task was reniced, its score doubles 1258 * superuser or direct hardware access tasks (CAP_SYS_ADMIN, CAP_SYS_RESOURCE 1259 or CAP_SYS_RAWIO) have their score divided by 4 1260 * if oom condition happened in one cpuset and checked process does not belong 1261 to it, its score is divided by 8 1262 * the resulting score is multiplied by two to the power of oom_adj, i.e. 1263 points <<= oom_adj when it is positive and 1264 points >>= -(oom_adj) otherwise 1265 1266 The task with the highest badness score is then selected and its children 1267 are killed, process itself will be killed in an OOM situation when it does 1268 not have children or some of them disabled oom like described above. 1269 1270 3.2 /proc/<pid>/oom_score - Display current oom-killer score 1271 ------------------------------------------------------------- 1272 1273 This file can be used to check the current score used by the oom-killer is for 1274 any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which 1275 process should be killed in an out-of-memory situation. 1276 1277 1278 3.3 /proc/<pid>/io - Display the IO accounting fields 1279 ------------------------------------------------------- 1280 1281 This file contains IO statistics for each running process 1282 1283 Example 1284 ------- 1285 1286 test:/tmp # dd if=/dev/zero of=/tmp/test.dat & 1287 [1] 3828 1288 1289 test:/tmp # cat /proc/3828/io 1290 rchar: 323934931 1291 wchar: 323929600 1292 syscr: 632687 1293 syscw: 632675 1294 read_bytes: 0 1295 write_bytes: 323932160 1296 cancelled_write_bytes: 0 1297 1298 1299 Description 1300 ----------- 1301 1302 rchar 1303 ----- 1304 1305 I/O counter: chars read 1306 The number of bytes which this task has caused to be read from storage. This 1307 is simply the sum of bytes which this process passed to read() and pread(). 1308 It includes things like tty IO and it is unaffected by whether or not actual 1309 physical disk IO was required (the read might have been satisfied from 1310 pagecache) 1311 1312 1313 wchar 1314 ----- 1315 1316 I/O counter: chars written 1317 The number of bytes which this task has caused, or shall cause to be written 1318 to disk. Similar caveats apply here as with rchar. 1319 1320 1321 syscr 1322 ----- 1323 1324 I/O counter: read syscalls 1325 Attempt to count the number of read I/O operations, i.e. syscalls like read() 1326 and pread(). 1327 1328 1329 syscw 1330 ----- 1331 1332 I/O counter: write syscalls 1333 Attempt to count the number of write I/O operations, i.e. syscalls like 1334 write() and pwrite(). 1335 1336 1337 read_bytes 1338 ---------- 1339 1340 I/O counter: bytes read 1341 Attempt to count the number of bytes which this process really did cause to 1342 be fetched from the storage layer. Done at the submit_bio() level, so it is 1343 accurate for block-backed filesystems. <please add status regarding NFS and 1344 CIFS at a later time> 1345 1346 1347 write_bytes 1348 ----------- 1349 1350 I/O counter: bytes written 1351 Attempt to count the number of bytes which this process caused to be sent to 1352 the storage layer. This is done at page-dirtying time. 1353 1354 1355 cancelled_write_bytes 1356 --------------------- 1357 1358 The big inaccuracy here is truncate. If a process writes 1MB to a file and 1359 then deletes the file, it will in fact perform no writeout. But it will have 1360 been accounted as having caused 1MB of write. 1361 In other words: The number of bytes which this process caused to not happen, 1362 by truncating pagecache. A task can cause "negative" IO too. If this task 1363 truncates some dirty pagecache, some IO which another task has been accounted 1364 for (in it's write_bytes) will not be happening. We _could_ just subtract that 1365 from the truncating task's write_bytes, but there is information loss in doing 1366 that. 1367 1368 1369 Note 1370 ---- 1371 1372 At its current implementation state, this is a bit racy on 32-bit machines: if 1373 process A reads process B's /proc/pid/io while process B is updating one of 1374 those 64-bit counters, process A could see an intermediate result. 1375 1376 1377 More information about this can be found within the taskstats documentation in 1378 Documentation/accounting. 1379 1380 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings 1381 --------------------------------------------------------------- 1382 When a process is dumped, all anonymous memory is written to a core file as 1383 long as the size of the core file isn't limited. But sometimes we don't want 1384 to dump some memory segments, for example, huge shared memory. Conversely, 1385 sometimes we want to save file-backed memory segments into a core file, not 1386 only the individual files. 1387 1388 /proc/<pid>/coredump_filter allows you to customize which memory segments 1389 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 1390 of memory types. If a bit of the bitmask is set, memory segments of the 1391 corresponding memory type are dumped, otherwise they are not dumped. 1392 1393 The following 7 memory types are supported: 1394 - (bit 0) anonymous private memory 1395 - (bit 1) anonymous shared memory 1396 - (bit 2) file-backed private memory 1397 - (bit 3) file-backed shared memory 1398 - (bit 4) ELF header pages in file-backed private memory areas (it is 1399 effective only if the bit 2 is cleared) 1400 - (bit 5) hugetlb private memory 1401 - (bit 6) hugetlb shared memory 1402 1403 Note that MMIO pages such as frame buffer are never dumped and vDSO pages 1404 are always dumped regardless of the bitmask status. 1405 1406 Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only 1407 effected by bit 5-6. 1408 1409 Default value of coredump_filter is 0x23; this means all anonymous memory 1410 segments and hugetlb private memory are dumped. 1411 1412 If you don't want to dump all shared memory segments attached to pid 1234, 1413 write 0x21 to the process's proc file. 1414 1415 $ echo 0x21 > /proc/1234/coredump_filter 1416 1417 When a new process is created, the process inherits the bitmask status from its 1418 parent. It is useful to set up coredump_filter before the program runs. 1419 For example: 1420 1421 $ echo 0x7 > /proc/self/coredump_filter 1422 $ ./some_program 1423 1424 3.5 /proc/<pid>/mountinfo - Information about mounts 1425 -------------------------------------------------------- 1426 1427 This file contains lines of the form: 1428 1429 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue 1430 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) 1431 1432 (1) mount ID: unique identifier of the mount (may be reused after umount) 1433 (2) parent ID: ID of parent (or of self for the top of the mount tree) 1434 (3) major:minor: value of st_dev for files on filesystem 1435 (4) root: root of the mount within the filesystem 1436 (5) mount point: mount point relative to the process's root 1437 (6) mount options: per mount options 1438 (7) optional fields: zero or more fields of the form "tag[:value]" 1439 (8) separator: marks the end of the optional fields 1440 (9) filesystem type: name of filesystem of the form "type[.subtype]" 1441 (10) mount source: filesystem specific information or "none" 1442 (11) super options: per super block options 1443 1444 Parsers should ignore all unrecognised optional fields. Currently the 1445 possible optional fields are: 1446 1447 shared:X mount is shared in peer group X 1448 master:X mount is slave to peer group X 1449 propagate_from:X mount is slave and receives propagation from peer group X (*) 1450 unbindable mount is unbindable 1451 1452 (*) X is the closest dominant peer group under the process's root. If 1453 X is the immediate master of the mount, or if there's no dominant peer 1454 group under the same root, then only the "master:X" field is present 1455 and not the "propagate_from:X" field. 1456 1457 For more information on mount propagation see: 1458 1459 Documentation/filesystems/sharedsubtree.txt 1460 1461 1462 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm 1463 -------------------------------------------------------- 1464 These files provide a method to access a tasks comm value. It also allows for 1465 a task to set its own or one of its thread siblings comm value. The comm value 1466 is limited in size compared to the cmdline value, so writing anything longer 1467 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated 1468 comm value.
- [ filesystems ]
- 00-INDEX
- 9p.txt
- adfs.txt
- affs.txt
- afs.txt
- autofs4-mount-control.txt
- automount-support.txt
- befs.txt
- bfs.txt
- btrfs.txt
- [ caching ]
- ceph.txt
- cifs.txt
- coda.txt
- [ configfs ]
- cramfs.txt
- debugfs.txt
- dentry-locking.txt
- devpts.txt
- directory-locking
- dlmfs.txt
- dnotify.txt
- dnotify_test.c
- ecryptfs.txt
- exofs.txt
- ext2.txt
- ext3.txt
- ext4.txt
- fiemap.txt
- files.txt
- fuse.txt
- gfs2-glocks.txt
- gfs2-uevents.txt
- gfs2.txt
- hfs.txt
- hfsplus.txt
- hpfs.txt
- inotify.txt
- isofs.txt
- jfs.txt
- Locking
- locks.txt
- logfs.txt
- Makefile
- mandatory-locking.txt
- ncpfs.txt
- [ nfs ]
- nilfs2.txt
- ntfs.txt
- ocfs2.txt
- omfs.txt
- [ pohmelfs ]
- porting
- proc.txt
- quota.txt
- ramfs-rootfs-initramfs.txt
- relay.txt
- romfs.txt
- seq_file.txt
- sharedsubtree.txt
- smbfs.txt
- spufs.txt
- squashfs.txt
- sysfs-pci.txt
- sysfs.txt
- sysv-fs.txt
- tmpfs.txt
- ubifs.txt
- udf.txt
- ufs.txt
- vfat.txt
- vfs.txt
- xfs.txt
- xip.txt
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