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proc: partially revert "procfs: provide stack information for threads"

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Commit d899bf7b (procfs: provide stack information for threads) introduced
to show stack information in /proc/{pid}/status.  But it cause large
performance regression.  Unfortunately /proc/{pid}/status is used ps
command too and ps is one of most important component.  Because both to
take mmap_sem and page table walk are heavily operation.

If many process run, the ps performance is,

[before d899bf7b]

% perf stat ps >/dev/null

 Performance counter stats for 'ps':

     4090.435806  task-clock-msecs         #      0.032 CPUs
             229  context-switches         #      0.000 M/sec
               0  CPU-migrations           #      0.000 M/sec
             234  page-faults              #      0.000 M/sec
      8587565207  cycles                   #   2099.425 M/sec
      9866662403  instructions             #      1.149 IPC
      3789415411  cache-references         #    926.409 M/sec
        30419509  cache-misses             #      7.437 M/sec

   128.859521955  seconds time elapsed

[after d899bf7b]

% perf stat  ps  > /dev/null

 Performance counter stats for 'ps':

     4305.081146  task-clock-msecs         #      0.028 CPUs
             480  context-switches         #      0.000 M/sec
               2  CPU-migrations           #      0.000 M/sec
             237  page-faults              #      0.000 M/sec
      9021211334  cycles                   #   2095.480 M/sec
     10605887536  instructions             #      1.176 IPC
      3612650999  cache-references         #    839.160 M/sec
        23917502  cache-misses             #      5.556 M/sec

   152.277819582  seconds time elapsed

Thus, this patch revert it. Fortunately /proc/{pid}/task/{tid}/smaps
provide almost same information. we can use it.

Commit d899bf7b introduced two features:

 1) Add the annotattion of [thread stack: xxxx] mark to
    /proc/{pid}/task/{tid}/maps.
 2) Add StackUsage field to /proc/{pid}/status.

I only revert (2), because I haven't seen (1) cause regression.

Signed-off-by: KOSAKI Motohiro <[email protected]>
Cc: Stefani Seibold <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andi Kleen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
KOSAKI Motohiro 2010-01-08 14:42:56 -08:00 • committed by Linus Torvalds
commit 1306d603fc
2 changed files with 0 additions and 91 deletions
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2
Documentation/filesystems/proc.txt
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@ -177,7 +177,6 @@ read the file /proc/PID/status:
CapBnd: ffffffffffffffff
voluntary_ctxt_switches: 0
nonvoluntary_ctxt_switches: 1
Stack usage: 12 kB
This shows you nearly the same information you would get if you viewed it with
the ps command. In fact, ps uses the proc file system to obtain its
@ -231,7 +230,6 @@ Table 1-2: Contents of the statm files (as of 2.6.30-rc7)
Mems_allowed_list Same as previous, but in "list format"
voluntary_ctxt_switches number of voluntary context switches
nonvoluntary_ctxt_switches number of non voluntary context switches
Stack usage: stack usage high water mark (round up to page size)
..............................................................................
Table 1-3: Contents of the statm files (as of 2.6.8-rc3)