calcru: negative time ... followed by freeze
Robert Watson
rwatson at FreeBSD.org
Mon Jun 21 00:12:46 GMT 2004
I've now seen the following scenario happen several times in the last few
days while doing testing and benchmarking: I run a multi-threaded test,
such as super-smack, that causes a moderately high system load. I then
hit Ctrl-T or run top, or some other activity that forces calcru() to
execute. I will not infrequently get an extremely hard hang -- can't get
to DDB using serial break, etc. I don't remember it happening when using
non-threaded apps, so I'm wondering if there's a poor interaction with
KSE/scheduler/who knows what.
7:55PM up 6 mins, 2 users, load averages: 1.37, 0.91, 0.43
USER TTY FROM LOGIN@ IDLE WHAT
root d0 - 7:55PM - w
rwatson p0 cboss 7:50PM 2 super-smack
select-key
hippy# top
calcru: negative time of 1834075 usec for pid 654 (super-smack)
ca~~
In this case, I ran super-smack with the following parameters:
hippy:/usr/tmp/super-smack> super-smack select-key.smack 15 1000
This generates 15 workers, which should cause mysql to spawn off threads
as well. I'm running with stock libpthread on this system (slightly old)
but an up-to-date kernel from CVS, GENERIC.
Has anyone else seen this?
Robert N M Watson FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org Senior Research Scientist, McAfee Research
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