kern/78957: time counter per process stops (syscall: getrusage)
bde at zeta.org.au
Fri Mar 18 01:10:05 PST 2005
The following reply was made to PR kern/78957; it has been noted by GNATS.
From: Bruce Evans <bde at zeta.org.au>
To: Jakub Kruszona-Zawadzki <acid at gemius.pl>
Cc: freebsd-gnats-submit at freebsd.org, freebsd-bugs at freebsd.org
Subject: Re: kern/78957: time counter per process stops (syscall: getrusage)
Date: Fri, 18 Mar 2005 20:06:15 +1100 (EST)
On Thu, 17 Mar 2005, Jakub Kruszona-Zawadzki wrote:
> When a process is running for a long time (several days) time counter per process stops on value:
This may be the same bug as in PR 76972. Overflow occurs at about
48592008 ticks = 379625 seconds = 105 hours for a a process that consumes
100% of the CPU if the statclock frequency is 128 Hz (which is the default
and not easy to change). There is another overflow bug at 2^32 ticks = 388
days. This one is harder to fix. See PR 76972 for details and a fix for
the first overflow bug.
37965 seconds is a little larger than 305221 seconds. The difference might
be due to the other 70000+ seconds being in ru_stime.
The behaviour when overflow occurs is undefined, but stopping on a value
is quite likely to occur due to the algorithm for updating ru_*time.
Integer overflow tends to cause counters to reset to 0 (or INT_MIN),
but the kernel enforces monotonicity of the usage times, so they will
stick instead of going backwards to 0.
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