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SubjectRuntime accounting bug?
Hello,

I run two copies (dual processor system) of "mprime" from the GIMPS
project. After a while running (weeks?) the cumulative runtime reported by
top increments faster than real time, then after a while (unknown how long)
the value increments normally again. Then, maybe something overflows - but
runtime accounting stops entirely even though the process is in the run state.

(mprime is a cpu-bound low priority process like seti@home and friends.)

I presently have a stuck process and a one that should soon start to
increment faster than possible.

I have verified that the "stuck" process is indeed running since it continues
to generate output.

Here is the "stuck" process:

cat /proc/4126/stat; sleep 5; cat /proc/4126/stat
4126 (mprime) R 2984 4126 2984 34819 4126 4202496 16530 0 4 0 2124505930 661087 0 0 39 19 1 0 8442861 21483520 3733 4294967295 134512640 138881564 3220348480 3220345732 135248565 0 0 0 16386 0 0 0 17 1 0 0 0 0 0
4126 (mprime) R 2984 4126 2984 34819 4126 4202496 16530 0 4 0 2124505930 661087 0 0 39 19 1 0 8442861 21483520 3733 4294967295 134512640 138881564 3220348480 3220345736 135241038 0 0 0 16386 0 0 0 17 1 0 0 0 0 0


Here is the other process started more recently:

cat /proc/18312/stat; sleep 5; cat /proc/18312/stat
18312 (mprime) R 2969 18312 2969 34818 18312 4202496 7657 0 1 0 140549087 660363 0 0 39 19 1 0 346388363 35483648 7152 4294967295 134512640 138881564 3221166480 3221163732 135246526 0 0 0 16386 0 0 0 17 1 0 0 0 0 0
18312 (mprime) R 2969 18312 2969 34818 18312 4202496 7657 0 1 0 140549510 660364 0 0 39 19 1 0 346388363 35483648 7152 4294967295 134512640 138881564 3221166480 3221163740 135280398 0 0 0 16386 0 0 0 17 1 0 0 0 0 0


Top output sorted by cpu time:

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ TIME COMMAND
4126 zed 39 19 20980 14m 968 R 0 0.4 354194:30 5903h mprime
18312 zed 39 19 34652 27m 952 R 84 0.8 23544:49 392,24 mprime


uptime:
12:50:47 up 60 days, 18:58, 25 users, load average: 2.20, 2.21, 2.26

cat /proc/version
Linux version 2.6.25.1 (root@(none)) (gcc version 4.1.2) #3 SMP PREEMPT Tue
May 6 01:53:17 EDT 2008

The machine is a dual processor 1.2Ghz Athlon MP system. It's generally
problem free with maybe 1 bit error a year reported from the ecc ram.

As the problem takes so long to repeat I do not know how to approach it.
It has also been present for the past few kernels, since 2.6.23 if I
recall.

Anyone have any thoughts? It seems more cosmetic than critical.

George



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