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1 | ------------------------------------------------------------------------------ |
2 | T H E /proc F I L E S Y S T E M | |
3 | ------------------------------------------------------------------------------ | |
4 | /proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999 | |
5 | Bodo Bauer <bb@ricochet.net> | |
6 | ||
7 | 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000 | |
760df93e | 8 | move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009 |
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9 | ------------------------------------------------------------------------------ |
10 | Version 1.3 Kernel version 2.2.12 | |
11 | Kernel version 2.4.0-test11-pre4 | |
12 | ------------------------------------------------------------------------------ | |
13 | ||
14 | Table of Contents | |
15 | ----------------- | |
16 | ||
17 | 0 Preface | |
18 | 0.1 Introduction/Credits | |
19 | 0.2 Legal Stuff | |
20 | ||
21 | 1 Collecting System Information | |
22 | 1.1 Process-Specific Subdirectories | |
23 | 1.2 Kernel data | |
24 | 1.3 IDE devices in /proc/ide | |
25 | 1.4 Networking info in /proc/net | |
26 | 1.5 SCSI info | |
27 | 1.6 Parallel port info in /proc/parport | |
28 | 1.7 TTY info in /proc/tty | |
29 | 1.8 Miscellaneous kernel statistics in /proc/stat | |
760df93e | 30 | 1.9 Ext4 file system parameters |
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31 | |
32 | 2 Modifying System Parameters | |
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33 | |
34 | 3 Per-Process Parameters | |
35 | 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score | |
36 | 3.2 /proc/<pid>/oom_score - Display current oom-killer score | |
37 | 3.3 /proc/<pid>/io - Display the IO accounting fields | |
38 | 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings | |
39 | 3.5 /proc/<pid>/mountinfo - Information about mounts | |
40 | ||
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41 | |
42 | ------------------------------------------------------------------------------ | |
43 | Preface | |
44 | ------------------------------------------------------------------------------ | |
45 | ||
46 | 0.1 Introduction/Credits | |
47 | ------------------------ | |
48 | ||
49 | This documentation is part of a soon (or so we hope) to be released book on | |
50 | the SuSE Linux distribution. As there is no complete documentation for the | |
51 | /proc file system and we've used many freely available sources to write these | |
52 | chapters, it seems only fair to give the work back to the Linux community. | |
53 | This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm | |
54 | afraid it's still far from complete, but we hope it will be useful. As far as | |
55 | we know, it is the first 'all-in-one' document about the /proc file system. It | |
56 | is focused on the Intel x86 hardware, so if you are looking for PPC, ARM, | |
57 | SPARC, AXP, etc., features, you probably won't find what you are looking for. | |
58 | It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But | |
59 | additions and patches are welcome and will be added to this document if you | |
60 | mail them to Bodo. | |
61 | ||
62 | We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of | |
63 | other people for help compiling this documentation. We'd also like to extend a | |
64 | special thank you to Andi Kleen for documentation, which we relied on heavily | |
65 | to create this document, as well as the additional information he provided. | |
66 | Thanks to everybody else who contributed source or docs to the Linux kernel | |
67 | and helped create a great piece of software... :) | |
68 | ||
69 | If you have any comments, corrections or additions, please don't hesitate to | |
70 | contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this | |
71 | document. | |
72 | ||
73 | The latest version of this document is available online at | |
74 | http://skaro.nightcrawler.com/~bb/Docs/Proc as HTML version. | |
75 | ||
76 | If the above direction does not works for you, ypu could try the kernel | |
77 | mailing list at linux-kernel@vger.kernel.org and/or try to reach me at | |
78 | comandante@zaralinux.com. | |
79 | ||
80 | 0.2 Legal Stuff | |
81 | --------------- | |
82 | ||
83 | We don't guarantee the correctness of this document, and if you come to us | |
84 | complaining about how you screwed up your system because of incorrect | |
85 | documentation, we won't feel responsible... | |
86 | ||
87 | ------------------------------------------------------------------------------ | |
88 | CHAPTER 1: COLLECTING SYSTEM INFORMATION | |
89 | ------------------------------------------------------------------------------ | |
90 | ||
91 | ------------------------------------------------------------------------------ | |
92 | In This Chapter | |
93 | ------------------------------------------------------------------------------ | |
94 | * Investigating the properties of the pseudo file system /proc and its | |
95 | ability to provide information on the running Linux system | |
96 | * Examining /proc's structure | |
97 | * Uncovering various information about the kernel and the processes running | |
98 | on the system | |
99 | ------------------------------------------------------------------------------ | |
100 | ||
101 | ||
102 | The proc file system acts as an interface to internal data structures in the | |
103 | kernel. It can be used to obtain information about the system and to change | |
104 | certain kernel parameters at runtime (sysctl). | |
105 | ||
106 | First, we'll take a look at the read-only parts of /proc. In Chapter 2, we | |
107 | show you how you can use /proc/sys to change settings. | |
108 | ||
109 | 1.1 Process-Specific Subdirectories | |
110 | ----------------------------------- | |
111 | ||
112 | The directory /proc contains (among other things) one subdirectory for each | |
113 | process running on the system, which is named after the process ID (PID). | |
114 | ||
115 | The link self points to the process reading the file system. Each process | |
116 | subdirectory has the entries listed in Table 1-1. | |
117 | ||
118 | ||
119 | Table 1-1: Process specific entries in /proc | |
120 | .............................................................................. | |
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121 | File Content |
122 | clear_refs Clears page referenced bits shown in smaps output | |
123 | cmdline Command line arguments | |
124 | cpu Current and last cpu in which it was executed (2.4)(smp) | |
125 | cwd Link to the current working directory | |
126 | environ Values of environment variables | |
127 | exe Link to the executable of this process | |
128 | fd Directory, which contains all file descriptors | |
129 | maps Memory maps to executables and library files (2.4) | |
130 | mem Memory held by this process | |
131 | root Link to the root directory of this process | |
132 | stat Process status | |
133 | statm Process memory status information | |
134 | status Process status in human readable form | |
135 | wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan | |
2ec220e2 | 136 | stack Report full stack trace, enable via CONFIG_STACKTRACE |
b813e931 | 137 | smaps Extension based on maps, the rss size for each mapped file |
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138 | .............................................................................. |
139 | ||
140 | For example, to get the status information of a process, all you have to do is | |
141 | read the file /proc/PID/status: | |
142 | ||
143 | >cat /proc/self/status | |
144 | Name: cat | |
145 | State: R (running) | |
146 | Pid: 5452 | |
147 | PPid: 743 | |
148 | TracerPid: 0 (2.4) | |
149 | Uid: 501 501 501 501 | |
150 | Gid: 100 100 100 100 | |
151 | Groups: 100 14 16 | |
152 | VmSize: 1112 kB | |
153 | VmLck: 0 kB | |
154 | VmRSS: 348 kB | |
155 | VmData: 24 kB | |
156 | VmStk: 12 kB | |
157 | VmExe: 8 kB | |
158 | VmLib: 1044 kB | |
159 | SigPnd: 0000000000000000 | |
160 | SigBlk: 0000000000000000 | |
161 | SigIgn: 0000000000000000 | |
162 | SigCgt: 0000000000000000 | |
163 | CapInh: 00000000fffffeff | |
164 | CapPrm: 0000000000000000 | |
165 | CapEff: 0000000000000000 | |
166 | ||
167 | ||
168 | This shows you nearly the same information you would get if you viewed it with | |
169 | the ps command. In fact, ps uses the proc file system to obtain its | |
170 | information. The statm file contains more detailed information about the | |
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171 | process memory usage. Its seven fields are explained in Table 1-2. The stat |
172 | file contains details information about the process itself. Its fields are | |
173 | explained in Table 1-3. | |
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174 | |
175 | ||
176 | Table 1-2: Contents of the statm files (as of 2.6.8-rc3) | |
177 | .............................................................................. | |
178 | Field Content | |
179 | size total program size (pages) (same as VmSize in status) | |
180 | resident size of memory portions (pages) (same as VmRSS in status) | |
181 | shared number of pages that are shared (i.e. backed by a file) | |
182 | trs number of pages that are 'code' (not including libs; broken, | |
183 | includes data segment) | |
184 | lrs number of pages of library (always 0 on 2.6) | |
185 | drs number of pages of data/stack (including libs; broken, | |
186 | includes library text) | |
187 | dt number of dirty pages (always 0 on 2.6) | |
188 | .............................................................................. | |
189 | ||
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190 | |
191 | Table 1-3: Contents of the stat files (as of 2.6.22-rc3) | |
192 | .............................................................................. | |
193 | Field Content | |
194 | pid process id | |
195 | tcomm filename of the executable | |
196 | state state (R is running, S is sleeping, D is sleeping in an | |
197 | uninterruptible wait, Z is zombie, T is traced or stopped) | |
198 | ppid process id of the parent process | |
199 | pgrp pgrp of the process | |
200 | sid session id | |
201 | tty_nr tty the process uses | |
202 | tty_pgrp pgrp of the tty | |
203 | flags task flags | |
204 | min_flt number of minor faults | |
205 | cmin_flt number of minor faults with child's | |
206 | maj_flt number of major faults | |
207 | cmaj_flt number of major faults with child's | |
208 | utime user mode jiffies | |
209 | stime kernel mode jiffies | |
210 | cutime user mode jiffies with child's | |
211 | cstime kernel mode jiffies with child's | |
212 | priority priority level | |
213 | nice nice level | |
214 | num_threads number of threads | |
2e01e00e | 215 | it_real_value (obsolete, always 0) |
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216 | start_time time the process started after system boot |
217 | vsize virtual memory size | |
218 | rss resident set memory size | |
219 | rsslim current limit in bytes on the rss | |
220 | start_code address above which program text can run | |
221 | end_code address below which program text can run | |
222 | start_stack address of the start of the stack | |
223 | esp current value of ESP | |
224 | eip current value of EIP | |
225 | pending bitmap of pending signals (obsolete) | |
226 | blocked bitmap of blocked signals (obsolete) | |
227 | sigign bitmap of ignored signals (obsolete) | |
228 | sigcatch bitmap of catched signals (obsolete) | |
229 | wchan address where process went to sleep | |
230 | 0 (place holder) | |
231 | 0 (place holder) | |
232 | exit_signal signal to send to parent thread on exit | |
233 | task_cpu which CPU the task is scheduled on | |
234 | rt_priority realtime priority | |
235 | policy scheduling policy (man sched_setscheduler) | |
236 | blkio_ticks time spent waiting for block IO | |
237 | .............................................................................. | |
238 | ||
239 | ||
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240 | 1.2 Kernel data |
241 | --------------- | |
242 | ||
243 | Similar to the process entries, the kernel data files give information about | |
244 | the running kernel. The files used to obtain this information are contained in | |
18d96779 | 245 | /proc and are listed in Table 1-4. Not all of these will be present in your |
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246 | system. It depends on the kernel configuration and the loaded modules, which |
247 | files are there, and which are missing. | |
248 | ||
18d96779 | 249 | Table 1-4: Kernel info in /proc |
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250 | .............................................................................. |
251 | File Content | |
252 | apm Advanced power management info | |
253 | buddyinfo Kernel memory allocator information (see text) (2.5) | |
254 | bus Directory containing bus specific information | |
255 | cmdline Kernel command line | |
256 | cpuinfo Info about the CPU | |
257 | devices Available devices (block and character) | |
258 | dma Used DMS channels | |
259 | filesystems Supported filesystems | |
260 | driver Various drivers grouped here, currently rtc (2.4) | |
261 | execdomains Execdomains, related to security (2.4) | |
262 | fb Frame Buffer devices (2.4) | |
263 | fs File system parameters, currently nfs/exports (2.4) | |
264 | ide Directory containing info about the IDE subsystem | |
265 | interrupts Interrupt usage | |
266 | iomem Memory map (2.4) | |
267 | ioports I/O port usage | |
268 | irq Masks for irq to cpu affinity (2.4)(smp?) | |
269 | isapnp ISA PnP (Plug&Play) Info (2.4) | |
270 | kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4)) | |
271 | kmsg Kernel messages | |
272 | ksyms Kernel symbol table | |
273 | loadavg Load average of last 1, 5 & 15 minutes | |
274 | locks Kernel locks | |
275 | meminfo Memory info | |
276 | misc Miscellaneous | |
277 | modules List of loaded modules | |
278 | mounts Mounted filesystems | |
279 | net Networking info (see text) | |
280 | partitions Table of partitions known to the system | |
8b60756a | 281 | pci Deprecated info of PCI bus (new way -> /proc/bus/pci/, |
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282 | decoupled by lspci (2.4) |
283 | rtc Real time clock | |
284 | scsi SCSI info (see text) | |
285 | slabinfo Slab pool info | |
d3d64df2 | 286 | softirqs softirq usage |
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287 | stat Overall statistics |
288 | swaps Swap space utilization | |
289 | sys See chapter 2 | |
290 | sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4) | |
291 | tty Info of tty drivers | |
292 | uptime System uptime | |
293 | version Kernel version | |
294 | video bttv info of video resources (2.4) | |
a47a126a | 295 | vmallocinfo Show vmalloced areas |
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296 | .............................................................................. |
297 | ||
298 | You can, for example, check which interrupts are currently in use and what | |
299 | they are used for by looking in the file /proc/interrupts: | |
300 | ||
301 | > cat /proc/interrupts | |
302 | CPU0 | |
303 | 0: 8728810 XT-PIC timer | |
304 | 1: 895 XT-PIC keyboard | |
305 | 2: 0 XT-PIC cascade | |
306 | 3: 531695 XT-PIC aha152x | |
307 | 4: 2014133 XT-PIC serial | |
308 | 5: 44401 XT-PIC pcnet_cs | |
309 | 8: 2 XT-PIC rtc | |
310 | 11: 8 XT-PIC i82365 | |
311 | 12: 182918 XT-PIC PS/2 Mouse | |
312 | 13: 1 XT-PIC fpu | |
313 | 14: 1232265 XT-PIC ide0 | |
314 | 15: 7 XT-PIC ide1 | |
315 | NMI: 0 | |
316 | ||
317 | In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the | |
318 | output of a SMP machine): | |
319 | ||
320 | > cat /proc/interrupts | |
321 | ||
322 | CPU0 CPU1 | |
323 | 0: 1243498 1214548 IO-APIC-edge timer | |
324 | 1: 8949 8958 IO-APIC-edge keyboard | |
325 | 2: 0 0 XT-PIC cascade | |
326 | 5: 11286 10161 IO-APIC-edge soundblaster | |
327 | 8: 1 0 IO-APIC-edge rtc | |
328 | 9: 27422 27407 IO-APIC-edge 3c503 | |
329 | 12: 113645 113873 IO-APIC-edge PS/2 Mouse | |
330 | 13: 0 0 XT-PIC fpu | |
331 | 14: 22491 24012 IO-APIC-edge ide0 | |
332 | 15: 2183 2415 IO-APIC-edge ide1 | |
333 | 17: 30564 30414 IO-APIC-level eth0 | |
334 | 18: 177 164 IO-APIC-level bttv | |
335 | NMI: 2457961 2457959 | |
336 | LOC: 2457882 2457881 | |
337 | ERR: 2155 | |
338 | ||
339 | NMI is incremented in this case because every timer interrupt generates a NMI | |
340 | (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups. | |
341 | ||
342 | LOC is the local interrupt counter of the internal APIC of every CPU. | |
343 | ||
344 | ERR is incremented in the case of errors in the IO-APIC bus (the bus that | |
345 | connects the CPUs in a SMP system. This means that an error has been detected, | |
346 | the IO-APIC automatically retry the transmission, so it should not be a big | |
347 | problem, but you should read the SMP-FAQ. | |
348 | ||
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349 | In 2.6.2* /proc/interrupts was expanded again. This time the goal was for |
350 | /proc/interrupts to display every IRQ vector in use by the system, not | |
351 | just those considered 'most important'. The new vectors are: | |
352 | ||
353 | THR -- interrupt raised when a machine check threshold counter | |
354 | (typically counting ECC corrected errors of memory or cache) exceeds | |
355 | a configurable threshold. Only available on some systems. | |
356 | ||
357 | TRM -- a thermal event interrupt occurs when a temperature threshold | |
358 | has been exceeded for the CPU. This interrupt may also be generated | |
359 | when the temperature drops back to normal. | |
360 | ||
361 | SPU -- a spurious interrupt is some interrupt that was raised then lowered | |
362 | by some IO device before it could be fully processed by the APIC. Hence | |
363 | the APIC sees the interrupt but does not know what device it came from. | |
364 | For this case the APIC will generate the interrupt with a IRQ vector | |
365 | of 0xff. This might also be generated by chipset bugs. | |
366 | ||
367 | RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are | |
368 | sent from one CPU to another per the needs of the OS. Typically, | |
369 | their statistics are used by kernel developers and interested users to | |
19f59460 | 370 | determine the occurrence of interrupts of the given type. |
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371 | |
372 | The above IRQ vectors are displayed only when relevent. For example, | |
373 | the threshold vector does not exist on x86_64 platforms. Others are | |
374 | suppressed when the system is a uniprocessor. As of this writing, only | |
375 | i386 and x86_64 platforms support the new IRQ vector displays. | |
376 | ||
377 | Of some interest is the introduction of the /proc/irq directory to 2.4. | |
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378 | It could be used to set IRQ to CPU affinity, this means that you can "hook" an |
379 | IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the | |
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380 | irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and |
381 | prof_cpu_mask. | |
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382 | |
383 | For example | |
384 | > ls /proc/irq/ | |
385 | 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask | |
18404756 | 386 | 1 11 13 15 17 19 3 5 7 9 default_smp_affinity |
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387 | > ls /proc/irq/0/ |
388 | smp_affinity | |
389 | ||
18404756 MK |
390 | smp_affinity is a bitmask, in which you can specify which CPUs can handle the |
391 | IRQ, you can set it by doing: | |
1da177e4 | 392 | |
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393 | > echo 1 > /proc/irq/10/smp_affinity |
394 | ||
395 | This means that only the first CPU will handle the IRQ, but you can also echo | |
396 | 5 which means that only the first and fourth CPU can handle the IRQ. | |
1da177e4 | 397 | |
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398 | The contents of each smp_affinity file is the same by default: |
399 | ||
400 | > cat /proc/irq/0/smp_affinity | |
401 | ffffffff | |
1da177e4 | 402 | |
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403 | The default_smp_affinity mask applies to all non-active IRQs, which are the |
404 | IRQs which have not yet been allocated/activated, and hence which lack a | |
405 | /proc/irq/[0-9]* directory. | |
1da177e4 | 406 | |
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407 | prof_cpu_mask specifies which CPUs are to be profiled by the system wide |
408 | profiler. Default value is ffffffff (all cpus). | |
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409 | |
410 | The way IRQs are routed is handled by the IO-APIC, and it's Round Robin | |
411 | between all the CPUs which are allowed to handle it. As usual the kernel has | |
412 | more info than you and does a better job than you, so the defaults are the | |
413 | best choice for almost everyone. | |
414 | ||
415 | There are three more important subdirectories in /proc: net, scsi, and sys. | |
416 | The general rule is that the contents, or even the existence of these | |
417 | directories, depend on your kernel configuration. If SCSI is not enabled, the | |
418 | directory scsi may not exist. The same is true with the net, which is there | |
419 | only when networking support is present in the running kernel. | |
420 | ||
421 | The slabinfo file gives information about memory usage at the slab level. | |
422 | Linux uses slab pools for memory management above page level in version 2.2. | |
423 | Commonly used objects have their own slab pool (such as network buffers, | |
424 | directory cache, and so on). | |
425 | ||
426 | .............................................................................. | |
427 | ||
428 | > cat /proc/buddyinfo | |
429 | ||
430 | Node 0, zone DMA 0 4 5 4 4 3 ... | |
431 | Node 0, zone Normal 1 0 0 1 101 8 ... | |
432 | Node 0, zone HighMem 2 0 0 1 1 0 ... | |
433 | ||
434 | Memory fragmentation is a problem under some workloads, and buddyinfo is a | |
435 | useful tool for helping diagnose these problems. Buddyinfo will give you a | |
436 | clue as to how big an area you can safely allocate, or why a previous | |
437 | allocation failed. | |
438 | ||
439 | Each column represents the number of pages of a certain order which are | |
440 | available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in | |
441 | ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE | |
442 | available in ZONE_NORMAL, etc... | |
443 | ||
444 | .............................................................................. | |
445 | ||
446 | meminfo: | |
447 | ||
448 | Provides information about distribution and utilization of memory. This | |
449 | varies by architecture and compile options. The following is from a | |
450 | 16GB PIII, which has highmem enabled. You may not have all of these fields. | |
451 | ||
452 | > cat /proc/meminfo | |
453 | ||
454 | ||
455 | MemTotal: 16344972 kB | |
456 | MemFree: 13634064 kB | |
457 | Buffers: 3656 kB | |
458 | Cached: 1195708 kB | |
459 | SwapCached: 0 kB | |
460 | Active: 891636 kB | |
461 | Inactive: 1077224 kB | |
462 | HighTotal: 15597528 kB | |
463 | HighFree: 13629632 kB | |
464 | LowTotal: 747444 kB | |
465 | LowFree: 4432 kB | |
466 | SwapTotal: 0 kB | |
467 | SwapFree: 0 kB | |
468 | Dirty: 968 kB | |
469 | Writeback: 0 kB | |
b88473f7 | 470 | AnonPages: 861800 kB |
1da177e4 | 471 | Mapped: 280372 kB |
b88473f7 MS |
472 | Slab: 284364 kB |
473 | SReclaimable: 159856 kB | |
474 | SUnreclaim: 124508 kB | |
475 | PageTables: 24448 kB | |
476 | NFS_Unstable: 0 kB | |
477 | Bounce: 0 kB | |
478 | WritebackTmp: 0 kB | |
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479 | CommitLimit: 7669796 kB |
480 | Committed_AS: 100056 kB | |
1da177e4 LT |
481 | VmallocTotal: 112216 kB |
482 | VmallocUsed: 428 kB | |
483 | VmallocChunk: 111088 kB | |
484 | ||
485 | MemTotal: Total usable ram (i.e. physical ram minus a few reserved | |
486 | bits and the kernel binary code) | |
487 | MemFree: The sum of LowFree+HighFree | |
488 | Buffers: Relatively temporary storage for raw disk blocks | |
489 | shouldn't get tremendously large (20MB or so) | |
490 | Cached: in-memory cache for files read from the disk (the | |
491 | pagecache). Doesn't include SwapCached | |
492 | SwapCached: Memory that once was swapped out, is swapped back in but | |
493 | still also is in the swapfile (if memory is needed it | |
494 | doesn't need to be swapped out AGAIN because it is already | |
495 | in the swapfile. This saves I/O) | |
496 | Active: Memory that has been used more recently and usually not | |
497 | reclaimed unless absolutely necessary. | |
498 | Inactive: Memory which has been less recently used. It is more | |
499 | eligible to be reclaimed for other purposes | |
500 | HighTotal: | |
501 | HighFree: Highmem is all memory above ~860MB of physical memory | |
502 | Highmem areas are for use by userspace programs, or | |
503 | for the pagecache. The kernel must use tricks to access | |
504 | this memory, making it slower to access than lowmem. | |
505 | LowTotal: | |
506 | LowFree: Lowmem is memory which can be used for everything that | |
3f6dee9b | 507 | highmem can be used for, but it is also available for the |
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508 | kernel's use for its own data structures. Among many |
509 | other things, it is where everything from the Slab is | |
510 | allocated. Bad things happen when you're out of lowmem. | |
511 | SwapTotal: total amount of swap space available | |
512 | SwapFree: Memory which has been evicted from RAM, and is temporarily | |
513 | on the disk | |
514 | Dirty: Memory which is waiting to get written back to the disk | |
515 | Writeback: Memory which is actively being written back to the disk | |
b88473f7 | 516 | AnonPages: Non-file backed pages mapped into userspace page tables |
1da177e4 | 517 | Mapped: files which have been mmaped, such as libraries |
e82443c0 | 518 | Slab: in-kernel data structures cache |
b88473f7 MS |
519 | SReclaimable: Part of Slab, that might be reclaimed, such as caches |
520 | SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure | |
521 | PageTables: amount of memory dedicated to the lowest level of page | |
522 | tables. | |
523 | NFS_Unstable: NFS pages sent to the server, but not yet committed to stable | |
524 | storage | |
525 | Bounce: Memory used for block device "bounce buffers" | |
526 | WritebackTmp: Memory used by FUSE for temporary writeback buffers | |
1da177e4 LT |
527 | CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'), |
528 | this is the total amount of memory currently available to | |
529 | be allocated on the system. This limit is only adhered to | |
530 | if strict overcommit accounting is enabled (mode 2 in | |
531 | 'vm.overcommit_memory'). | |
532 | The CommitLimit is calculated with the following formula: | |
533 | CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap | |
534 | For example, on a system with 1G of physical RAM and 7G | |
535 | of swap with a `vm.overcommit_ratio` of 30 it would | |
536 | yield a CommitLimit of 7.3G. | |
537 | For more details, see the memory overcommit documentation | |
538 | in vm/overcommit-accounting. | |
539 | Committed_AS: The amount of memory presently allocated on the system. | |
540 | The committed memory is a sum of all of the memory which | |
541 | has been allocated by processes, even if it has not been | |
542 | "used" by them as of yet. A process which malloc()'s 1G | |
543 | of memory, but only touches 300M of it will only show up | |
544 | as using 300M of memory even if it has the address space | |
545 | allocated for the entire 1G. This 1G is memory which has | |
546 | been "committed" to by the VM and can be used at any time | |
547 | by the allocating application. With strict overcommit | |
548 | enabled on the system (mode 2 in 'vm.overcommit_memory'), | |
549 | allocations which would exceed the CommitLimit (detailed | |
550 | above) will not be permitted. This is useful if one needs | |
551 | to guarantee that processes will not fail due to lack of | |
552 | memory once that memory has been successfully allocated. | |
1da177e4 LT |
553 | VmallocTotal: total size of vmalloc memory area |
554 | VmallocUsed: amount of vmalloc area which is used | |
19f59460 | 555 | VmallocChunk: largest contiguous block of vmalloc area which is free |
1da177e4 | 556 | |
a47a126a ED |
557 | .............................................................................. |
558 | ||
559 | vmallocinfo: | |
560 | ||
561 | Provides information about vmalloced/vmaped areas. One line per area, | |
562 | containing the virtual address range of the area, size in bytes, | |
563 | caller information of the creator, and optional information depending | |
564 | on the kind of area : | |
565 | ||
566 | pages=nr number of pages | |
567 | phys=addr if a physical address was specified | |
568 | ioremap I/O mapping (ioremap() and friends) | |
569 | vmalloc vmalloc() area | |
570 | vmap vmap()ed pages | |
571 | user VM_USERMAP area | |
572 | vpages buffer for pages pointers was vmalloced (huge area) | |
573 | N<node>=nr (Only on NUMA kernels) | |
574 | Number of pages allocated on memory node <node> | |
575 | ||
576 | > cat /proc/vmallocinfo | |
577 | 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ... | |
578 | /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128 | |
579 | 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ... | |
580 | /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64 | |
581 | 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f... | |
582 | phys=7fee8000 ioremap | |
583 | 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f... | |
584 | phys=7fee7000 ioremap | |
585 | 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210 | |
586 | 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ... | |
587 | /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3 | |
588 | 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ... | |
589 | pages=2 vmalloc N1=2 | |
590 | 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ... | |
591 | /0x130 [x_tables] pages=4 vmalloc N0=4 | |
592 | 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ... | |
593 | pages=14 vmalloc N2=14 | |
594 | 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ... | |
595 | pages=4 vmalloc N1=4 | |
596 | 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ... | |
597 | pages=2 vmalloc N1=2 | |
598 | 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ... | |
599 | pages=10 vmalloc N0=10 | |
1da177e4 | 600 | |
d3d64df2 KK |
601 | .............................................................................. |
602 | ||
603 | softirqs: | |
604 | ||
605 | Provides counts of softirq handlers serviced since boot time, for each cpu. | |
606 | ||
607 | > cat /proc/softirqs | |
608 | CPU0 CPU1 CPU2 CPU3 | |
609 | HI: 0 0 0 0 | |
610 | TIMER: 27166 27120 27097 27034 | |
611 | NET_TX: 0 0 0 17 | |
612 | NET_RX: 42 0 0 39 | |
613 | BLOCK: 0 0 107 1121 | |
614 | TASKLET: 0 0 0 290 | |
615 | SCHED: 27035 26983 26971 26746 | |
616 | HRTIMER: 0 0 0 0 | |
617 | RCU: 1678 1769 2178 2250 | |
618 | ||
619 | ||
1da177e4 LT |
620 | 1.3 IDE devices in /proc/ide |
621 | ---------------------------- | |
622 | ||
623 | The subdirectory /proc/ide contains information about all IDE devices of which | |
624 | the kernel is aware. There is one subdirectory for each IDE controller, the | |
625 | file drivers and a link for each IDE device, pointing to the device directory | |
626 | in the controller specific subtree. | |
627 | ||
628 | The file drivers contains general information about the drivers used for the | |
629 | IDE devices: | |
630 | ||
631 | > cat /proc/ide/drivers | |
632 | ide-cdrom version 4.53 | |
633 | ide-disk version 1.08 | |
634 | ||
635 | More detailed information can be found in the controller specific | |
636 | subdirectories. These are named ide0, ide1 and so on. Each of these | |
18d96779 | 637 | directories contains the files shown in table 1-5. |
1da177e4 LT |
638 | |
639 | ||
18d96779 | 640 | Table 1-5: IDE controller info in /proc/ide/ide? |
1da177e4 LT |
641 | .............................................................................. |
642 | File Content | |
643 | channel IDE channel (0 or 1) | |
644 | config Configuration (only for PCI/IDE bridge) | |
645 | mate Mate name | |
646 | model Type/Chipset of IDE controller | |
647 | .............................................................................. | |
648 | ||
649 | Each device connected to a controller has a separate subdirectory in the | |
18d96779 | 650 | controllers directory. The files listed in table 1-6 are contained in these |
1da177e4 LT |
651 | directories. |
652 | ||
653 | ||
18d96779 | 654 | Table 1-6: IDE device information |
1da177e4 LT |
655 | .............................................................................. |
656 | File Content | |
657 | cache The cache | |
658 | capacity Capacity of the medium (in 512Byte blocks) | |
659 | driver driver and version | |
660 | geometry physical and logical geometry | |
661 | identify device identify block | |
662 | media media type | |
663 | model device identifier | |
664 | settings device setup | |
665 | smart_thresholds IDE disk management thresholds | |
666 | smart_values IDE disk management values | |
667 | .............................................................................. | |
668 | ||
669 | The most interesting file is settings. This file contains a nice overview of | |
670 | the drive parameters: | |
671 | ||
672 | # cat /proc/ide/ide0/hda/settings | |
673 | name value min max mode | |
674 | ---- ----- --- --- ---- | |
675 | bios_cyl 526 0 65535 rw | |
676 | bios_head 255 0 255 rw | |
677 | bios_sect 63 0 63 rw | |
678 | breada_readahead 4 0 127 rw | |
679 | bswap 0 0 1 r | |
680 | file_readahead 72 0 2097151 rw | |
681 | io_32bit 0 0 3 rw | |
682 | keepsettings 0 0 1 rw | |
683 | max_kb_per_request 122 1 127 rw | |
684 | multcount 0 0 8 rw | |
685 | nice1 1 0 1 rw | |
686 | nowerr 0 0 1 rw | |
687 | pio_mode write-only 0 255 w | |
688 | slow 0 0 1 rw | |
689 | unmaskirq 0 0 1 rw | |
690 | using_dma 0 0 1 rw | |
691 | ||
692 | ||
693 | 1.4 Networking info in /proc/net | |
694 | -------------------------------- | |
695 | ||
696 | The subdirectory /proc/net follows the usual pattern. Table 1-6 shows the | |
697 | additional values you get for IP version 6 if you configure the kernel to | |
698 | support this. Table 1-7 lists the files and their meaning. | |
699 | ||
700 | ||
701 | Table 1-6: IPv6 info in /proc/net | |
702 | .............................................................................. | |
703 | File Content | |
704 | udp6 UDP sockets (IPv6) | |
705 | tcp6 TCP sockets (IPv6) | |
706 | raw6 Raw device statistics (IPv6) | |
707 | igmp6 IP multicast addresses, which this host joined (IPv6) | |
708 | if_inet6 List of IPv6 interface addresses | |
709 | ipv6_route Kernel routing table for IPv6 | |
710 | rt6_stats Global IPv6 routing tables statistics | |
711 | sockstat6 Socket statistics (IPv6) | |
712 | snmp6 Snmp data (IPv6) | |
713 | .............................................................................. | |
714 | ||
715 | ||
716 | Table 1-7: Network info in /proc/net | |
717 | .............................................................................. | |
718 | File Content | |
719 | arp Kernel ARP table | |
720 | dev network devices with statistics | |
721 | dev_mcast the Layer2 multicast groups a device is listening too | |
722 | (interface index, label, number of references, number of bound | |
723 | addresses). | |
724 | dev_stat network device status | |
725 | ip_fwchains Firewall chain linkage | |
726 | ip_fwnames Firewall chain names | |
727 | ip_masq Directory containing the masquerading tables | |
728 | ip_masquerade Major masquerading table | |
729 | netstat Network statistics | |
730 | raw raw device statistics | |
731 | route Kernel routing table | |
732 | rpc Directory containing rpc info | |
733 | rt_cache Routing cache | |
734 | snmp SNMP data | |
735 | sockstat Socket statistics | |
736 | tcp TCP sockets | |
737 | tr_rif Token ring RIF routing table | |
738 | udp UDP sockets | |
739 | unix UNIX domain sockets | |
740 | wireless Wireless interface data (Wavelan etc) | |
741 | igmp IP multicast addresses, which this host joined | |
742 | psched Global packet scheduler parameters. | |
743 | netlink List of PF_NETLINK sockets | |
744 | ip_mr_vifs List of multicast virtual interfaces | |
745 | ip_mr_cache List of multicast routing cache | |
746 | .............................................................................. | |
747 | ||
748 | You can use this information to see which network devices are available in | |
749 | your system and how much traffic was routed over those devices: | |
750 | ||
751 | > cat /proc/net/dev | |
752 | Inter-|Receive |[... | |
753 | face |bytes packets errs drop fifo frame compressed multicast|[... | |
754 | lo: 908188 5596 0 0 0 0 0 0 [... | |
755 | ppp0:15475140 20721 410 0 0 410 0 0 [... | |
756 | eth0: 614530 7085 0 0 0 0 0 1 [... | |
757 | ||
758 | ...] Transmit | |
759 | ...] bytes packets errs drop fifo colls carrier compressed | |
760 | ...] 908188 5596 0 0 0 0 0 0 | |
761 | ...] 1375103 17405 0 0 0 0 0 0 | |
762 | ...] 1703981 5535 0 0 0 3 0 0 | |
763 | ||
764 | In addition, each Channel Bond interface has it's own directory. For | |
765 | example, the bond0 device will have a directory called /proc/net/bond0/. | |
766 | It will contain information that is specific to that bond, such as the | |
767 | current slaves of the bond, the link status of the slaves, and how | |
768 | many times the slaves link has failed. | |
769 | ||
770 | 1.5 SCSI info | |
771 | ------------- | |
772 | ||
773 | If you have a SCSI host adapter in your system, you'll find a subdirectory | |
774 | named after the driver for this adapter in /proc/scsi. You'll also see a list | |
775 | of all recognized SCSI devices in /proc/scsi: | |
776 | ||
777 | >cat /proc/scsi/scsi | |
778 | Attached devices: | |
779 | Host: scsi0 Channel: 00 Id: 00 Lun: 00 | |
780 | Vendor: IBM Model: DGHS09U Rev: 03E0 | |
781 | Type: Direct-Access ANSI SCSI revision: 03 | |
782 | Host: scsi0 Channel: 00 Id: 06 Lun: 00 | |
783 | Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04 | |
784 | Type: CD-ROM ANSI SCSI revision: 02 | |
785 | ||
786 | ||
787 | The directory named after the driver has one file for each adapter found in | |
788 | the system. These files contain information about the controller, including | |
789 | the used IRQ and the IO address range. The amount of information shown is | |
790 | dependent on the adapter you use. The example shows the output for an Adaptec | |
791 | AHA-2940 SCSI adapter: | |
792 | ||
793 | > cat /proc/scsi/aic7xxx/0 | |
794 | ||
795 | Adaptec AIC7xxx driver version: 5.1.19/3.2.4 | |
796 | Compile Options: | |
797 | TCQ Enabled By Default : Disabled | |
798 | AIC7XXX_PROC_STATS : Disabled | |
799 | AIC7XXX_RESET_DELAY : 5 | |
800 | Adapter Configuration: | |
801 | SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter | |
802 | Ultra Wide Controller | |
803 | PCI MMAPed I/O Base: 0xeb001000 | |
804 | Adapter SEEPROM Config: SEEPROM found and used. | |
805 | Adaptec SCSI BIOS: Enabled | |
806 | IRQ: 10 | |
807 | SCBs: Active 0, Max Active 2, | |
808 | Allocated 15, HW 16, Page 255 | |
809 | Interrupts: 160328 | |
810 | BIOS Control Word: 0x18b6 | |
811 | Adapter Control Word: 0x005b | |
812 | Extended Translation: Enabled | |
813 | Disconnect Enable Flags: 0xffff | |
814 | Ultra Enable Flags: 0x0001 | |
815 | Tag Queue Enable Flags: 0x0000 | |
816 | Ordered Queue Tag Flags: 0x0000 | |
817 | Default Tag Queue Depth: 8 | |
818 | Tagged Queue By Device array for aic7xxx host instance 0: | |
819 | {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255} | |
820 | Actual queue depth per device for aic7xxx host instance 0: | |
821 | {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1} | |
822 | Statistics: | |
823 | (scsi0:0:0:0) | |
824 | Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8 | |
825 | Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0) | |
826 | Total transfers 160151 (74577 reads and 85574 writes) | |
827 | (scsi0:0:6:0) | |
828 | Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15 | |
829 | Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0) | |
830 | Total transfers 0 (0 reads and 0 writes) | |
831 | ||
832 | ||
833 | 1.6 Parallel port info in /proc/parport | |
834 | --------------------------------------- | |
835 | ||
836 | The directory /proc/parport contains information about the parallel ports of | |
837 | your system. It has one subdirectory for each port, named after the port | |
838 | number (0,1,2,...). | |
839 | ||
840 | These directories contain the four files shown in Table 1-8. | |
841 | ||
842 | ||
843 | Table 1-8: Files in /proc/parport | |
844 | .............................................................................. | |
845 | File Content | |
846 | autoprobe Any IEEE-1284 device ID information that has been acquired. | |
847 | devices list of the device drivers using that port. A + will appear by the | |
848 | name of the device currently using the port (it might not appear | |
849 | against any). | |
850 | hardware Parallel port's base address, IRQ line and DMA channel. | |
851 | irq IRQ that parport is using for that port. This is in a separate | |
852 | file to allow you to alter it by writing a new value in (IRQ | |
853 | number or none). | |
854 | .............................................................................. | |
855 | ||
856 | 1.7 TTY info in /proc/tty | |
857 | ------------------------- | |
858 | ||
859 | Information about the available and actually used tty's can be found in the | |
860 | directory /proc/tty.You'll find entries for drivers and line disciplines in | |
861 | this directory, as shown in Table 1-9. | |
862 | ||
863 | ||
864 | Table 1-9: Files in /proc/tty | |
865 | .............................................................................. | |
866 | File Content | |
867 | drivers list of drivers and their usage | |
868 | ldiscs registered line disciplines | |
869 | driver/serial usage statistic and status of single tty lines | |
870 | .............................................................................. | |
871 | ||
872 | To see which tty's are currently in use, you can simply look into the file | |
873 | /proc/tty/drivers: | |
874 | ||
875 | > cat /proc/tty/drivers | |
876 | pty_slave /dev/pts 136 0-255 pty:slave | |
877 | pty_master /dev/ptm 128 0-255 pty:master | |
878 | pty_slave /dev/ttyp 3 0-255 pty:slave | |
879 | pty_master /dev/pty 2 0-255 pty:master | |
880 | serial /dev/cua 5 64-67 serial:callout | |
881 | serial /dev/ttyS 4 64-67 serial | |
882 | /dev/tty0 /dev/tty0 4 0 system:vtmaster | |
883 | /dev/ptmx /dev/ptmx 5 2 system | |
884 | /dev/console /dev/console 5 1 system:console | |
885 | /dev/tty /dev/tty 5 0 system:/dev/tty | |
886 | unknown /dev/tty 4 1-63 console | |
887 | ||
888 | ||
889 | 1.8 Miscellaneous kernel statistics in /proc/stat | |
890 | ------------------------------------------------- | |
891 | ||
892 | Various pieces of information about kernel activity are available in the | |
893 | /proc/stat file. All of the numbers reported in this file are aggregates | |
894 | since the system first booted. For a quick look, simply cat the file: | |
895 | ||
896 | > cat /proc/stat | |
b68f2c3a LC |
897 | cpu 2255 34 2290 22625563 6290 127 456 0 |
898 | cpu0 1132 34 1441 11311718 3675 127 438 0 | |
899 | cpu1 1123 0 849 11313845 2614 0 18 0 | |
1da177e4 LT |
900 | intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...] |
901 | ctxt 1990473 | |
902 | btime 1062191376 | |
903 | processes 2915 | |
904 | procs_running 1 | |
905 | procs_blocked 0 | |
d3d64df2 | 906 | softirq 183433 0 21755 12 39 1137 231 21459 2263 |
1da177e4 LT |
907 | |
908 | The very first "cpu" line aggregates the numbers in all of the other "cpuN" | |
909 | lines. These numbers identify the amount of time the CPU has spent performing | |
910 | different kinds of work. Time units are in USER_HZ (typically hundredths of a | |
911 | second). The meanings of the columns are as follows, from left to right: | |
912 | ||
913 | - user: normal processes executing in user mode | |
914 | - nice: niced processes executing in user mode | |
915 | - system: processes executing in kernel mode | |
916 | - idle: twiddling thumbs | |
917 | - iowait: waiting for I/O to complete | |
918 | - irq: servicing interrupts | |
919 | - softirq: servicing softirqs | |
b68f2c3a | 920 | - steal: involuntary wait |
1da177e4 LT |
921 | |
922 | The "intr" line gives counts of interrupts serviced since boot time, for each | |
923 | of the possible system interrupts. The first column is the total of all | |
924 | interrupts serviced; each subsequent column is the total for that particular | |
925 | interrupt. | |
926 | ||
927 | The "ctxt" line gives the total number of context switches across all CPUs. | |
928 | ||
929 | The "btime" line gives the time at which the system booted, in seconds since | |
930 | the Unix epoch. | |
931 | ||
932 | The "processes" line gives the number of processes and threads created, which | |
933 | includes (but is not limited to) those created by calls to the fork() and | |
934 | clone() system calls. | |
935 | ||
936 | The "procs_running" line gives the number of processes currently running on | |
937 | CPUs. | |
938 | ||
939 | The "procs_blocked" line gives the number of processes currently blocked, | |
940 | waiting for I/O to complete. | |
941 | ||
d3d64df2 KK |
942 | The "softirq" line gives counts of softirqs serviced since boot time, for each |
943 | of the possible system softirqs. The first column is the total of all | |
944 | softirqs serviced; each subsequent column is the total for that particular | |
945 | softirq. | |
946 | ||
37515fac | 947 | |
c9de560d AT |
948 | 1.9 Ext4 file system parameters |
949 | ------------------------------ | |
37515fac TT |
950 | |
951 | Information about mounted ext4 file systems can be found in | |
952 | /proc/fs/ext4. Each mounted filesystem will have a directory in | |
953 | /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or | |
954 | /proc/fs/ext4/dm-0). The files in each per-device directory are shown | |
955 | in Table 1-10, below. | |
956 | ||
957 | Table 1-10: Files in /proc/fs/ext4/<devname> | |
958 | .............................................................................. | |
959 | File Content | |
960 | mb_groups details of multiblock allocator buddy cache of free blocks | |
961 | mb_history multiblock allocation history | |
37515fac TT |
962 | .............................................................................. |
963 | ||
1da177e4 LT |
964 | |
965 | ------------------------------------------------------------------------------ | |
966 | Summary | |
967 | ------------------------------------------------------------------------------ | |
968 | The /proc file system serves information about the running system. It not only | |
969 | allows access to process data but also allows you to request the kernel status | |
970 | by reading files in the hierarchy. | |
971 | ||
972 | The directory structure of /proc reflects the types of information and makes | |
973 | it easy, if not obvious, where to look for specific data. | |
974 | ------------------------------------------------------------------------------ | |
975 | ||
976 | ------------------------------------------------------------------------------ | |
977 | CHAPTER 2: MODIFYING SYSTEM PARAMETERS | |
978 | ------------------------------------------------------------------------------ | |
979 | ||
980 | ------------------------------------------------------------------------------ | |
981 | In This Chapter | |
982 | ------------------------------------------------------------------------------ | |
983 | * Modifying kernel parameters by writing into files found in /proc/sys | |
984 | * Exploring the files which modify certain parameters | |
985 | * Review of the /proc/sys file tree | |
986 | ------------------------------------------------------------------------------ | |
987 | ||
988 | ||
989 | A very interesting part of /proc is the directory /proc/sys. This is not only | |
990 | a source of information, it also allows you to change parameters within the | |
991 | kernel. Be very careful when attempting this. You can optimize your system, | |
992 | but you can also cause it to crash. Never alter kernel parameters on a | |
993 | production system. Set up a development machine and test to make sure that | |
994 | everything works the way you want it to. You may have no alternative but to | |
995 | reboot the machine once an error has been made. | |
996 | ||
997 | To change a value, simply echo the new value into the file. An example is | |
998 | given below in the section on the file system data. You need to be root to do | |
999 | this. You can create your own boot script to perform this every time your | |
1000 | system boots. | |
1001 | ||
1002 | The files in /proc/sys can be used to fine tune and monitor miscellaneous and | |
1003 | general things in the operation of the Linux kernel. Since some of the files | |
1004 | can inadvertently disrupt your system, it is advisable to read both | |
1005 | documentation and source before actually making adjustments. In any case, be | |
1006 | very careful when writing to any of these files. The entries in /proc may | |
1007 | change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt | |
1008 | review the kernel documentation in the directory /usr/src/linux/Documentation. | |
1009 | This chapter is heavily based on the documentation included in the pre 2.2 | |
1010 | kernels, and became part of it in version 2.2.1 of the Linux kernel. | |
1011 | ||
760df93e | 1012 | Please see: Documentation/sysctls/ directory for descriptions of these |
db0fb184 | 1013 | entries. |
9d0243bc | 1014 | |
760df93e SF |
1015 | ------------------------------------------------------------------------------ |
1016 | Summary | |
1017 | ------------------------------------------------------------------------------ | |
1018 | Certain aspects of kernel behavior can be modified at runtime, without the | |
1019 | need to recompile the kernel, or even to reboot the system. The files in the | |
1020 | /proc/sys tree can not only be read, but also modified. You can use the echo | |
1021 | command to write value into these files, thereby changing the default settings | |
1022 | of the kernel. | |
1023 | ------------------------------------------------------------------------------ | |
9d0243bc | 1024 | |
760df93e SF |
1025 | ------------------------------------------------------------------------------ |
1026 | CHAPTER 3: PER-PROCESS PARAMETERS | |
1027 | ------------------------------------------------------------------------------ | |
1da177e4 | 1028 | |
760df93e | 1029 | 3.1 /proc/<pid>/oom_adj - Adjust the oom-killer score |
d7ff0dbf JFM |
1030 | ------------------------------------------------------ |
1031 | ||
2ff05b2b DR |
1032 | This file can be used to adjust the score used to select which processes should |
1033 | be killed in an out-of-memory situation. The oom_adj value is a characteristic | |
1034 | of the task's mm, so all threads that share an mm with pid will have the same | |
1035 | oom_adj value. A high value will increase the likelihood of this process being | |
1036 | killed by the oom-killer. Valid values are in the range -16 to +15 as | |
1037 | explained below and a special value of -17, which disables oom-killing | |
1038 | altogether for threads sharing pid's mm. | |
d7ff0dbf | 1039 | |
9e9e3cbc EP |
1040 | The process to be killed in an out-of-memory situation is selected among all others |
1041 | based on its badness score. This value equals the original memory size of the process | |
1042 | and is then updated according to its CPU time (utime + stime) and the | |
1043 | run time (uptime - start time). The longer it runs the smaller is the score. | |
1044 | Badness score is divided by the square root of the CPU time and then by | |
1045 | the double square root of the run time. | |
1046 | ||
1047 | Swapped out tasks are killed first. Half of each child's memory size is added to | |
1048 | the parent's score if they do not share the same memory. Thus forking servers | |
1049 | are the prime candidates to be killed. Having only one 'hungry' child will make | |
1050 | parent less preferable than the child. | |
1051 | ||
2ff05b2b DR |
1052 | /proc/<pid>/oom_adj cannot be changed for kthreads since they are immune from |
1053 | oom-killing already. | |
1054 | ||
9e9e3cbc EP |
1055 | /proc/<pid>/oom_score shows process' current badness score. |
1056 | ||
1057 | The following heuristics are then applied: | |
1058 | * if the task was reniced, its score doubles | |
1059 | * superuser or direct hardware access tasks (CAP_SYS_ADMIN, CAP_SYS_RESOURCE | |
1060 | or CAP_SYS_RAWIO) have their score divided by 4 | |
1061 | * if oom condition happened in one cpuset and checked task does not belong | |
1062 | to it, its score is divided by 8 | |
1063 | * the resulting score is multiplied by two to the power of oom_adj, i.e. | |
1064 | points <<= oom_adj when it is positive and | |
1065 | points >>= -(oom_adj) otherwise | |
1066 | ||
1067 | The task with the highest badness score is then selected and its children | |
1068 | are killed, process itself will be killed in an OOM situation when it does | |
1069 | not have children or some of them disabled oom like described above. | |
1070 | ||
760df93e | 1071 | 3.2 /proc/<pid>/oom_score - Display current oom-killer score |
d7ff0dbf JFM |
1072 | ------------------------------------------------------------- |
1073 | ||
d7ff0dbf JFM |
1074 | This file can be used to check the current score used by the oom-killer is for |
1075 | any given <pid>. Use it together with /proc/<pid>/oom_adj to tune which | |
1076 | process should be killed in an out-of-memory situation. | |
1da177e4 | 1077 | |
f9c99463 | 1078 | |
760df93e | 1079 | 3.3 /proc/<pid>/io - Display the IO accounting fields |
f9c99463 RK |
1080 | ------------------------------------------------------- |
1081 | ||
1082 | This file contains IO statistics for each running process | |
1083 | ||
1084 | Example | |
1085 | ------- | |
1086 | ||
1087 | test:/tmp # dd if=/dev/zero of=/tmp/test.dat & | |
1088 | [1] 3828 | |
1089 | ||
1090 | test:/tmp # cat /proc/3828/io | |
1091 | rchar: 323934931 | |
1092 | wchar: 323929600 | |
1093 | syscr: 632687 | |
1094 | syscw: 632675 | |
1095 | read_bytes: 0 | |
1096 | write_bytes: 323932160 | |
1097 | cancelled_write_bytes: 0 | |
1098 | ||
1099 | ||
1100 | Description | |
1101 | ----------- | |
1102 | ||
1103 | rchar | |
1104 | ----- | |
1105 | ||
1106 | I/O counter: chars read | |
1107 | The number of bytes which this task has caused to be read from storage. This | |
1108 | is simply the sum of bytes which this process passed to read() and pread(). | |
1109 | It includes things like tty IO and it is unaffected by whether or not actual | |
1110 | physical disk IO was required (the read might have been satisfied from | |
1111 | pagecache) | |
1112 | ||
1113 | ||
1114 | wchar | |
1115 | ----- | |
1116 | ||
1117 | I/O counter: chars written | |
1118 | The number of bytes which this task has caused, or shall cause to be written | |
1119 | to disk. Similar caveats apply here as with rchar. | |
1120 | ||
1121 | ||
1122 | syscr | |
1123 | ----- | |
1124 | ||
1125 | I/O counter: read syscalls | |
1126 | Attempt to count the number of read I/O operations, i.e. syscalls like read() | |
1127 | and pread(). | |
1128 | ||
1129 | ||
1130 | syscw | |
1131 | ----- | |
1132 | ||
1133 | I/O counter: write syscalls | |
1134 | Attempt to count the number of write I/O operations, i.e. syscalls like | |
1135 | write() and pwrite(). | |
1136 | ||
1137 | ||
1138 | read_bytes | |
1139 | ---------- | |
1140 | ||
1141 | I/O counter: bytes read | |
1142 | Attempt to count the number of bytes which this process really did cause to | |
1143 | be fetched from the storage layer. Done at the submit_bio() level, so it is | |
1144 | accurate for block-backed filesystems. <please add status regarding NFS and | |
1145 | CIFS at a later time> | |
1146 | ||
1147 | ||
1148 | write_bytes | |
1149 | ----------- | |
1150 | ||
1151 | I/O counter: bytes written | |
1152 | Attempt to count the number of bytes which this process caused to be sent to | |
1153 | the storage layer. This is done at page-dirtying time. | |
1154 | ||
1155 | ||
1156 | cancelled_write_bytes | |
1157 | --------------------- | |
1158 | ||
1159 | The big inaccuracy here is truncate. If a process writes 1MB to a file and | |
1160 | then deletes the file, it will in fact perform no writeout. But it will have | |
1161 | been accounted as having caused 1MB of write. | |
1162 | In other words: The number of bytes which this process caused to not happen, | |
1163 | by truncating pagecache. A task can cause "negative" IO too. If this task | |
1164 | truncates some dirty pagecache, some IO which another task has been accounted | |
1165 | for (in it's write_bytes) will not be happening. We _could_ just subtract that | |
1166 | from the truncating task's write_bytes, but there is information loss in doing | |
1167 | that. | |
1168 | ||
1169 | ||
1170 | Note | |
1171 | ---- | |
1172 | ||
1173 | At its current implementation state, this is a bit racy on 32-bit machines: if | |
1174 | process A reads process B's /proc/pid/io while process B is updating one of | |
1175 | those 64-bit counters, process A could see an intermediate result. | |
1176 | ||
1177 | ||
1178 | More information about this can be found within the taskstats documentation in | |
1179 | Documentation/accounting. | |
1180 | ||
760df93e | 1181 | 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings |
bb90110d KH |
1182 | --------------------------------------------------------------- |
1183 | When a process is dumped, all anonymous memory is written to a core file as | |
1184 | long as the size of the core file isn't limited. But sometimes we don't want | |
1185 | to dump some memory segments, for example, huge shared memory. Conversely, | |
1186 | sometimes we want to save file-backed memory segments into a core file, not | |
1187 | only the individual files. | |
1188 | ||
1189 | /proc/<pid>/coredump_filter allows you to customize which memory segments | |
1190 | will be dumped when the <pid> process is dumped. coredump_filter is a bitmask | |
1191 | of memory types. If a bit of the bitmask is set, memory segments of the | |
1192 | corresponding memory type are dumped, otherwise they are not dumped. | |
1193 | ||
e575f111 | 1194 | The following 7 memory types are supported: |
bb90110d KH |
1195 | - (bit 0) anonymous private memory |
1196 | - (bit 1) anonymous shared memory | |
1197 | - (bit 2) file-backed private memory | |
1198 | - (bit 3) file-backed shared memory | |
b261dfea HK |
1199 | - (bit 4) ELF header pages in file-backed private memory areas (it is |
1200 | effective only if the bit 2 is cleared) | |
e575f111 KM |
1201 | - (bit 5) hugetlb private memory |
1202 | - (bit 6) hugetlb shared memory | |
bb90110d KH |
1203 | |
1204 | Note that MMIO pages such as frame buffer are never dumped and vDSO pages | |
1205 | are always dumped regardless of the bitmask status. | |
1206 | ||
e575f111 KM |
1207 | Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only |
1208 | effected by bit 5-6. | |
1209 | ||
1210 | Default value of coredump_filter is 0x23; this means all anonymous memory | |
1211 | segments and hugetlb private memory are dumped. | |
bb90110d KH |
1212 | |
1213 | If you don't want to dump all shared memory segments attached to pid 1234, | |
e575f111 | 1214 | write 0x21 to the process's proc file. |
bb90110d | 1215 | |
e575f111 | 1216 | $ echo 0x21 > /proc/1234/coredump_filter |
bb90110d KH |
1217 | |
1218 | When a new process is created, the process inherits the bitmask status from its | |
1219 | parent. It is useful to set up coredump_filter before the program runs. | |
1220 | For example: | |
1221 | ||
1222 | $ echo 0x7 > /proc/self/coredump_filter | |
1223 | $ ./some_program | |
1224 | ||
760df93e | 1225 | 3.5 /proc/<pid>/mountinfo - Information about mounts |
2d4d4864 RP |
1226 | -------------------------------------------------------- |
1227 | ||
1228 | This file contains lines of the form: | |
1229 | ||
1230 | 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue | |
1231 | (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) | |
1232 | ||
1233 | (1) mount ID: unique identifier of the mount (may be reused after umount) | |
1234 | (2) parent ID: ID of parent (or of self for the top of the mount tree) | |
1235 | (3) major:minor: value of st_dev for files on filesystem | |
1236 | (4) root: root of the mount within the filesystem | |
1237 | (5) mount point: mount point relative to the process's root | |
1238 | (6) mount options: per mount options | |
1239 | (7) optional fields: zero or more fields of the form "tag[:value]" | |
1240 | (8) separator: marks the end of the optional fields | |
1241 | (9) filesystem type: name of filesystem of the form "type[.subtype]" | |
1242 | (10) mount source: filesystem specific information or "none" | |
1243 | (11) super options: per super block options | |
1244 | ||
1245 | Parsers should ignore all unrecognised optional fields. Currently the | |
1246 | possible optional fields are: | |
1247 | ||
1248 | shared:X mount is shared in peer group X | |
1249 | master:X mount is slave to peer group X | |
97e7e0f7 | 1250 | propagate_from:X mount is slave and receives propagation from peer group X (*) |
2d4d4864 RP |
1251 | unbindable mount is unbindable |
1252 | ||
97e7e0f7 MS |
1253 | (*) X is the closest dominant peer group under the process's root. If |
1254 | X is the immediate master of the mount, or if there's no dominant peer | |
1255 | group under the same root, then only the "master:X" field is present | |
1256 | and not the "propagate_from:X" field. | |
1257 | ||
2d4d4864 RP |
1258 | For more information on mount propagation see: |
1259 | ||
1260 | Documentation/filesystems/sharedsubtree.txt | |
1261 |