From: Mike Galbraith <bitbucket@online.de>
To: Michael Wang <wangyun@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
peterz@infradead.org, mingo@kernel.org, a.p.zijlstra@chello.nl
Subject: Re: [RFC PATCH 0/2] sched: simplify the select_task_rq_fair()
Date: Thu, 24 Jan 2013 08:47:03 +0100 [thread overview]
Message-ID: <1359013623.5833.52.camel@marge.simpson.net> (raw)
In-Reply-To: <5100DF95.3020909@linux.vnet.ibm.com>
On Thu, 2013-01-24 at 15:15 +0800, Michael Wang wrote:
> On 01/24/2013 02:51 PM, Mike Galbraith wrote:
> > On Thu, 2013-01-24 at 14:01 +0800, Michael Wang wrote:
> >
> >> I've enabled WAKE flag on my box like you did, but still can't see
> >> regression, and I've just tested on a power server with 64 cpu, also
> >> failed to reproduce the issue (not compared with virgin yet, but can't
> >> see collapse).
> >
> > I'm not surprised. I'm seeing enough inconsistent crap to come to the
> > conclusion that stock scheduler knobs flat can't be used on a largish
> > box, they're just too preempt-happy, leading to weird crap.
> >
> > My 2 missing nodes came back, and the very same kernel that highly
> > repeatably collapsed with 2 nodes does not with 4 nodes, and 2 nodes
> > does not collapse with only preemption knob tweaking, and that's
> > bullshit. Virgin shows instability in the mid-range, make a tiny tweak
> > that should have little if any effect there, and that instability
> > vanishes entirely. Test runs are not consistent enough boot to boot etc
> > etc. Either stock knobs suck on NUMA boxen, or this box is possessed.
>
> Mike, I wonder the reason why change back to the old way make collapse
> away may not because there are logical error in new balance path, it's
> just changed the cost of select_task_rq(), whatever it's more or less,
> it's accidentally achieve the same effect as you tweak the knob, so
> that's the reason why it looks like old is better than new.
That's what I'm saying, it's a useless crap side-effect of a preempt
happy kernel. Results with these knobs are just not stable. Results go
wildly unstable with 2 nodes vs 4 in this box, but can be stabilized in
all with preemption knob adjustment.. or phase of moon might make them
appear stable.. or not.
-Mike
next prev parent reply other threads:[~2013-01-24 7:47 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1356588535-23251-1-git-send-email-wangyun@linux.vnet.ibm.com>
2013-01-09 9:28 ` Michael Wang
2013-01-12 8:01 ` Mike Galbraith
2013-01-12 10:19 ` Mike Galbraith
2013-01-14 9:21 ` Mike Galbraith
2013-01-15 3:10 ` Michael Wang
2013-01-15 4:52 ` Mike Galbraith
2013-01-15 8:26 ` Michael Wang
2013-01-17 5:55 ` Michael Wang
2013-01-20 4:09 ` Mike Galbraith
2013-01-21 2:50 ` Michael Wang
2013-01-21 4:38 ` Mike Galbraith
2013-01-21 5:07 ` Michael Wang
2013-01-21 6:42 ` Mike Galbraith
2013-01-21 7:09 ` Mike Galbraith
2013-01-21 7:45 ` Michael Wang
2013-01-21 9:09 ` Mike Galbraith
2013-01-21 9:22 ` Michael Wang
2013-01-21 9:44 ` Mike Galbraith
2013-01-21 10:30 ` Mike Galbraith
2013-01-22 3:43 ` Michael Wang
2013-01-22 8:03 ` Mike Galbraith
2013-01-22 8:56 ` Michael Wang
2013-01-22 11:34 ` Mike Galbraith
2013-01-23 3:01 ` Michael Wang
2013-01-23 5:02 ` Mike Galbraith
2013-01-22 14:41 ` Mike Galbraith
2013-01-23 2:44 ` Michael Wang
2013-01-23 4:31 ` Mike Galbraith
2013-01-23 5:09 ` Michael Wang
2013-01-23 6:28 ` Mike Galbraith
2013-01-23 7:10 ` Michael Wang
2013-01-23 8:20 ` Mike Galbraith
2013-01-23 8:30 ` Michael Wang
2013-01-23 8:49 ` Mike Galbraith
2013-01-23 9:00 ` Michael Wang
2013-01-23 9:18 ` Mike Galbraith
2013-01-23 9:26 ` Michael Wang
2013-01-23 9:37 ` Mike Galbraith
2013-01-23 9:32 ` Mike Galbraith
2013-01-24 6:01 ` Michael Wang
2013-01-24 6:51 ` Mike Galbraith
2013-01-24 7:15 ` Michael Wang
2013-01-24 7:47 ` Mike Galbraith [this message]
2013-01-24 8:14 ` Michael Wang
2013-01-24 9:07 ` Mike Galbraith
2013-01-24 9:26 ` Michael Wang
2013-01-24 10:34 ` Mike Galbraith
2013-01-25 2:14 ` Michael Wang
2013-01-24 7:00 ` Michael Wang
2013-01-21 7:34 ` Michael Wang
2013-01-21 8:26 ` Mike Galbraith
2013-01-21 8:46 ` Michael Wang
2013-01-21 9:11 ` Mike Galbraith
2013-01-15 2:46 ` Michael Wang
2013-01-11 8:15 Michael Wang
2013-01-11 10:13 ` Nikunj A Dadhania
2013-01-15 2:20 ` Michael Wang
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