From: "Chris Friesen" <cfriesen@nortel.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-kernel@vger.kernel.org, vatsa@linux.vnet.ibm.com,
mingo@elte.hu, pj@sgi.com
Subject: Re: fair group scheduler not so fair?
Date: Thu, 22 May 2008 14:02:19 -0600 [thread overview]
Message-ID: <4835D14B.20904@nortel.com> (raw)
In-Reply-To: <1211439417.29104.7.camel@twins>
Peter Zijlstra wrote:
> Could you see if the patches found here:
>
> http://programming.kicks-ass.net/kernel-patches/sched-smp-group-fixes/
>
> make any difference for you?
Not much difference. In the following case pid 2438 is in group "a" and
pids 2439/2440 are in group "b". Pid 2438 still gets stuck with only 66%.
2439 cfriesen 20 0 3800 392 336 R 99.7 0.0 3:17.37 cat
2438 cfriesen 20 0 3800 392 336 R 66.2 0.0 2:33.63 cat
2440 cfriesen 20 0 3800 392 336 R 33.6 0.0 1:47.53 cat
With 3 tasks in group a, 2 in group b, it's still pretty poor:
2514 cfriesen 20 0 3800 392 336 R 52.5 0.0 0:48.11 cat
2515 cfriesen 20 0 3800 392 336 R 50.2 0.0 0:42.53 cat
2439 cfriesen 20 0 3800 392 336 R 35.4 0.0 4:37.07 cat
2438 cfriesen 20 0 3800 392 336 R 33.3 0.0 3:34.97 cat
2440 cfriesen 20 0 3800 392 336 R 28.3 0.0 2:26.17 cat
If I boot with "nosmp" it behaves more or less as expected:
3 tasks in default:
2427 cfriesen 20 0 3800 392 336 R 33.7 0.0 0:36.54 cat
2429 cfriesen 20 0 3800 392 336 R 33.5 0.0 0:35.63 cat
2428 cfriesen 20 0 3800 392 336 R 32.9 0.0 0:35.84 cat
1 task in a, 2 in b:
2427 cfriesen 20 0 3800 392 336 R 49.8 0.0 1:45.74 cat
2428 cfriesen 20 0 3800 392 336 R 25.0 0.0 1:38.65 cat
2429 cfriesen 20 0 3800 392 336 R 25.0 0.0 1:38.18 cat
3 tasks in a, 2 in b:
2521 cfriesen 20 0 3800 392 336 R 25.2 0.0 0:08.52 cat
2522 cfriesen 20 0 3800 392 336 R 25.2 0.0 0:08.23 cat
2427 cfriesen 20 0 3800 392 336 R 16.6 0.0 1:59.39 cat
2429 cfriesen 20 0 3800 392 336 R 16.6 0.0 1:47.63 cat
2428 cfriesen 20 0 3800 392 336 R 16.4 0.0 1:48.65 cat
I haven't really dug into the scheduler yet (although that's next), but
based on these results it doesn't really look like the load balancer is
properly group-aware.
Chris
next prev parent reply other threads:[~2008-05-22 20:02 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-05-21 23:59 fair group scheduler not so fair? Chris Friesen
2008-05-22 6:56 ` Peter Zijlstra
2008-05-22 20:02 ` Chris Friesen [this message]
2008-05-22 20:07 ` Peter Zijlstra
2008-05-22 20:18 ` Li, Tong N
2008-05-22 21:13 ` Peter Zijlstra
2008-05-23 0:17 ` Chris Friesen
2008-05-23 7:44 ` Srivatsa Vaddagiri
2008-05-23 9:42 ` Srivatsa Vaddagiri
2008-05-23 9:39 ` Peter Zijlstra
2008-05-23 10:19 ` Srivatsa Vaddagiri
2008-05-23 10:16 ` Peter Zijlstra
2008-05-27 17:15 ` Srivatsa Vaddagiri
2008-05-27 18:13 ` Chris Friesen
2008-05-28 16:33 ` Srivatsa Vaddagiri
2008-05-28 18:35 ` Chris Friesen
2008-05-28 18:47 ` Dhaval Giani
2008-05-29 2:50 ` Srivatsa Vaddagiri
2008-05-29 16:46 ` Srivatsa Vaddagiri
2008-05-29 16:47 ` Srivatsa Vaddagiri
2008-05-29 21:30 ` Chris Friesen
2008-05-30 6:43 ` Dhaval Giani
2008-05-30 10:21 ` Srivatsa Vaddagiri
2008-05-30 11:36 ` Srivatsa Vaddagiri
2008-06-02 20:03 ` Chris Friesen
2008-05-27 17:28 ` Srivatsa Vaddagiri
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