From: David Newall <davidn@davidnewall.com>
To: Olaf Kirch <okir@suse.de>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
Andreas Gruenbacher <agruen@suse.de>
Subject: Re: CFS Performance Issues
Date: Fri, 29 May 2009 01:19:06 +0930 [thread overview]
Message-ID: <4A1EB272.3050902@davidnewall.com> (raw)
In-Reply-To: <200905281502.22487.okir@suse.de>
Olaf Kirch wrote:
> As you probably know, we've been chasing a variety of performance issues
> ...
> I see this:
>
> ./slice 16
> avg slice: 1.12 utime: 216263.187500
> ...
> Any insight you can offer here is greatly appreciated!
>
About that: avg slice is in nsec, not msec (the old, off-by-one-million
bug), and utime, also an average, is in usec.
The first result indicates 1.12 nsec per context switch, 193 context
switches and 346% CPU utilisation. You must have at least four CPU
cores. Here's your table, extended* per this interpretation:
./slice 16
avg slice: 1.12 utime: 216263.187500: 1.12 nsec/csw, 193 csw, 346 CPU%
avg slice: 0.25 utime: 125507.687500: 0.25 nsec/csw, 502 csw, 200 CPU%
avg slice: 0.31 utime: 125257.937500: 0.31 nsec/csw, 404 csw, 200 CPU%
avg slice: 0.31 utime: 125507.812500: 0.31 nsec/csw, 404 csw, 200 CPU%
avg slice: 0.12 utime: 124507.875000: 0.12 nsec/csw, 1037 csw, 199 CPU%
avg slice: 0.38 utime: 124757.687500: 0.38 nsec/csw, 328 csw, 199 CPU%
avg slice: 0.31 utime: 125508.000000: 0.31 nsec/csw, 404 csw, 200 CPU%
avg slice: 0.44 utime: 125757.750000: 0.44 nsec/csw, 285 csw, 201 CPU%
avg slice: 2.00 utime: 128258.000000: 2.00 nsec/csw, 64 csw, 205 CPU%
------ here I turned off new_fair_sleepers ----
avg slice: 10.25 utime: 137008.500000: 10.25 nsec/csw, 13 csw, 219 CPU%
avg slice: 9.31 utime: 139008.875000: 9.31 nsec/csw, 14 csw, 222 CPU%
avg slice: 10.50 utime: 141508.687500: 10.50 nsec/csw, 13 csw, 226 CPU%
avg slice: 9.44 utime: 139258.750000: 9.44 nsec/csw, 14 csw, 222 CPU%
avg slice: 10.31 utime: 140008.687500: 10.31 nsec/csw, 13 csw, 224 CPU%
avg slice: 9.19 utime: 139008.625000: 9.19 nsec/csw, 15 csw, 222 CPU%
avg slice: 10.00 utime: 137258.625000: 10.00 nsec/csw, 13 csw, 219 CPU%
avg slice: 10.06 utime: 135258.562500: 10.06 nsec/csw, 13 csw, 216 CPU%
avg slice: 9.62 utime: 138758.562500: 9.62 nsec/csw, 14 csw, 222 CPU%
You don't seem to be getting good CPU utilisation.
*awk '{printf "%s: %5.2f nsec/csw, %4d csw, %3d CPU%%\n", $0, $3, $5/$3/1000, $5*16/10000}'
next prev parent reply other threads:[~2009-05-28 15:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-05-28 13:02 CFS Performance Issues Olaf Kirch
2009-05-28 15:49 ` David Newall [this message]
2009-05-28 18:20 ` Olaf Kirch
2009-05-28 18:43 ` David Newall
2009-05-28 20:31 ` Peter Zijlstra
2009-05-30 11:18 ` Ingo Molnar
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