Package: procps
Version: 1:3.2.8-9
Severity: normal
I found a bug in reporting of CPU usage for a long running calculation on
a quad-core 64 bit machine.
While the calculation runs I monitor the process by running the
following command every 30 seconds:
ps -C elmfract -o args=,%cpu=,time=,rss=,vsz=,pid=
Below is a fragment of the logfile that shows where it goes wrong:
----
/home/eric/bin/elmfract F14 398 24-20:29:51 7733232 7989604 1771
/home/eric/bin/elmfract F14 398 24-20:31:51 7733232 7989604 1771
/home/eric/bin/elmfract F14 1712725 106751-23:47:16 7733232 7989604 1771
/home/eric/bin/elmfract F14 1719007 107149-12:01:11 7733232 7989604 1771
----
The first two lines show a CPU usage of 398%, i.e. practically 4 cores
busy. The second two lines show a CPU usage of 1712725%, suggesting
some 17127 busy cores. As it turns out, my machine does not have that
many cores :-). Also the reporting of 106751 cpu days used for the
calculation seems exagerated. The running process is not in the least
bit bothered, and produces correct results.
It happens after approximately 24*24*3600+20*3600+31*60+51 = 2147511 cpu
seconds were spent. This is very close to 2^31 milliseconds, which
hints at a signed 32 bit integer overflowing somewhere. Probably not
many people run calculations of several cpu weeks. The phenomenon is
reproducible, I have seen it with another long calculation, at exactly
the same moment.
The process itself reports its cpu usage using the times(2) system call,
as follows:
CPU (total) real: 178h 3m 6.43s,
usr: 38163h 3m 32.80s,
sys: 2542964h 7m 37.79s,
total: 2581127h 11m 10.59s
The user and system times obtained via times(2) are wrong, but the
elapsed time (measured by the times(2) return value) is OK.
My guess is that this may be a proc filesystem problem.
-- System Information:
Debian Release: 6.0.2
APT prefers stable-updates
APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)
Kernel: Linux 2.6.32-5-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Versions of packages procps depends on:
ii initscripts 2.88dsf-13.1 scripts for initializing and shutt
ii libc6 2.11.2-10 Embedded GNU C Library: Shared lib
ii libncurses5 5.7+20100313-5 shared libraries for terminal hand
ii libncursesw5 5.7+20100313-5 shared libraries for terminal hand
ii lsb-base 3.2-23.2squeeze1 Linux Standard Base 3.2 init scrip
Versions of packages procps recommends:
ii psmisc 22.11-1 utilities that use the proc file s
procps suggests no packages.
-- no debconf information
--
To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org
with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
