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[Bug 636290] New: The kernel reports wrong process user/sys time
  • From: bugzilla_noreply@xxxxxxxxxx
  • Date: Wed, 1 Sep 2010 15:11:57 +0000
  • Message-id: <bug-636290-21960@xxxxxxxxxxxxxxxxxxxxxxxx/>

https://bugzilla.novell.com/show_bug.cgi?id=636290

https://bugzilla.novell.com/show_bug.cgi?id=636290#c0


Summary: The kernel reports wrong process user/sys time
Classification: openSUSE
Product: openSUSE 11.3
Version: Final
Platform: x86
OS/Version: openSUSE 11.3
Status: NEW
Severity: Normal
Priority: P5 - None
Component: Kernel
AssignedTo: kernel-maintainers@xxxxxxxxxxxxxxxxxxxxxx
ReportedBy: alpar@xxxxxxxxxx
QAContact: qa@xxxxxxx
Found By: ---
Blocker: ---


User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.8)
Gecko/20100723 SUSE/3.6.8-0.1.1 Firefox/3.6.8

We have an algorithm implemented that does extensive calculations with almost
no syscalls. The kernel however reports it as system time:

$ time ./dimacs-solver i_n13.dimacs.int
Problem type: min
Num of nodes: 8181
Num of arcs: 739733

Sum of supply values: 0
GEQ supply contraints are used for NetworkSimplex

Read the file: u: 1.1s, s: 0.06s, cu: 0s, cs: 0s, real: 1.20954s
Setup NetworkSimplex class: u: 0.04s, s: 0.03s, cu: 0s, cs: 0s, real:
0.0795369s
Run NetworkSimplex: u: 13.83s, s: 189.24s, cu: 0s, cs: 0s, real: 204.291s

Feasible flow: found
Min flow cost: 847714917290

real 3m25.757s
user 0m14.987s
sys 3m9.338s


Above, the "Run NetworkSimplex" line shows the part of the execution that makes
no system call at all; still it is reported as being on the system level.

The output of strace confirms this clearly:

$ strace -tt -T ./build/tools/dimacs-solver i_n13.dimacs.int
[...]
16:58:22.722844 gettimeofday({1283353102, 722869}, NULL) = 0 <0.000031>
16:58:22.722950 times({tms_utime=115, tms_stime=9, tms_cutime=0, tms_cstime=0})
= 429597560 <0.000033>
16:58:22.745973 brk(0x8155000) = 0x8155000 <0.000021>
17:01:48.960355 gettimeofday({1283353308, 960428}, NULL) = 0 <0.000048>
17:01:48.960523 times({tms_utime=1801, tms_stime=18819, tms_cutime=0,
tms_cstime=0}) = 429618181 <0.000041>
17:01:48.960641 write(2, "Run NetworkSimplex: ", 20Run NetworkSimplex: ) = 20
<0.000042>
17:01:48.960748 write(2, "u: ", 3u: ) = 3 <0.000118>
17:01:48.960969 write(2, "16.86", 516.86) = 5 <0.000047>
17:01:48.961087 write(2, "s, s: ", 6s, s: ) = 6 <0.000045>
17:01:48.961203 write(2, "188.1", 5188.1) = 5 <0.000039>
17:01:48.961308 write(2, "s, cu: ", 7s, cu: ) = 7 <0.000032>
17:01:48.961402 write(2, "0", 10) = 1 <0.000034>
17:01:48.961491 write(2, "s, cs: ", 7s, cs: ) = 7 <0.000034>
17:01:48.961584 write(2, "0", 10) = 1 <0.000033>
17:01:48.961728 write(2, "s, real: ", 9s, real: ) = 9 <0.000036>
17:01:48.961830 write(2, "206.238", 7206.238) = 7 <0.000038>
17:01:48.961934 write(2, "s", 1s) = 1 <0.000041>
17:01:48.962033 write(2, "\n\n", 2
[...]


The source code of dimacs_solver is available at
http://lemon.cs.elte.hu/hg/lemon-main, the problem is reproducible at least
with g++-4.5 and g++-4.3

Reproducible: Always

Steps to Reproduce:
1. Download http://lime.cs.elte.hu/~alpar/dimacs-solver and
http://lime.cs.elte.hu/~alpar/i_n13.dimacs.int

2. Run

$ time ./dimacs-solver i_n13.dimacs.int

Actual Results:
Problem type: min
Num of nodes: 8181
Num of arcs: 739733

Sum of supply values: 0
GEQ supply contraints are used for NetworkSimplex

Read the file: u: 1.1s, s: 0.06s, cu: 0s, cs: 0s, real: 1.20954s
Setup NetworkSimplex class: u: 0.04s, s: 0.03s, cu: 0s, cs: 0s, real:
0.0795369s
Run NetworkSimplex: u: 13.83s, s: 189.24s, cu: 0s, cs: 0s, real: 204.291s

Feasible flow: found
Min flow cost: 847714917290

real 3m25.757s
user 0m14.987s
sys 3m9.338s



Expected Results:
Something like:

Problem type: min
Num of nodes: 8181
Num of arcs: 739733

Sum of supply values: 0
GEQ supply contraints are used for NetworkSimplex

Read the file: u: 1.1s, s: 0.06s, cu: 0s, cs: 0s, real: 1.20954s
Setup NetworkSimplex class: u: 0.04s, s: 0.03s, cu: 0s, cs: 0s, real:
0.0795369s
Run NetworkSimplex: u: 203.04s, s: 0.03s, cu: 0s, cs: 0s, real: 204.291s

Feasible flow: found
Min flow cost: 847714917290

real 3m25.757s
user 3m22.338s
sys 0m1.987s

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