From: Peter Zijlstra <peterz@infradead.org>
To: Yuyang Du <yuyang.du@intel.com>
Cc: bsegall@google.com, mingo@redhat.com,
linux-kernel@vger.kernel.org, rafael.j.wysocki@intel.com,
arjan.van.de.ven@intel.com, len.brown@intel.com,
alan.cox@intel.com, mark.gross@intel.com, pjt@google.com,
fengguang.wu@intel.com
Subject: Re: [PATCH 2/2] sched: Rewrite per entity runnable load average tracking
Date: Wed, 9 Jul 2014 20:45:43 +0200 [thread overview]
Message-ID: <20140709184543.GI9918@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20140709010753.GD25653@intel.com>
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On Wed, Jul 09, 2014 at 09:07:53AM +0800, Yuyang Du wrote:
> That is chalenging... Can someone (Peter) grant us a lock of the remote rq? :)
Nope :-).. we got rid of that lock for a good reason.
Also, this is one area where I feel performance really trumps
correctness, we can fudge the blocked load a little. So the
sched_clock_cpu() difference is a strict upper bound on the
rq_clock_task() difference (and under 'normal' circumstances shouldn't
be much off).
So we could simply use a timestamps from dequeue and one from enqueue,
and use that.
As to the remote subtraction, a RMW on another cacheline than the
rq->lock one should be good; esp since we don't actually observe the
per-rq total often (once per tick or so) I think, no?
The thing is, we do not want to disturb scheduling on whatever cpu the
task last ran on if we wake it to another cpu. Taking rq->lock wrecks
that for sure.
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next prev parent reply other threads:[~2014-07-09 18:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-02 2:30 [PATCH 1/2] sched: Remove update_rq_runnable_avg Yuyang Du
2014-07-02 2:30 ` [PATCH 2/2] sched: Rewrite per entity runnable load average tracking Yuyang Du
2014-07-07 10:07 ` Peter Zijlstra
2014-07-07 10:46 ` Peter Zijlstra
2014-07-07 20:03 ` Yuyang Du
2014-07-07 22:25 ` bsegall
2014-07-08 0:08 ` Yuyang Du
2014-07-08 17:04 ` bsegall
2014-07-09 1:07 ` Yuyang Du
2014-07-09 17:08 ` bsegall
2014-07-09 18:39 ` Yuyang Du
2014-07-09 18:45 ` Peter Zijlstra [this message]
2014-07-09 19:07 ` bsegall
2014-07-10 10:08 ` Peter Zijlstra
2014-07-10 17:01 ` bsegall
2014-07-10 19:53 ` Yuyang Du
2014-07-10 23:22 ` Yuyang Du
2014-07-11 8:47 ` Peter Zijlstra
2014-07-11 0:52 ` Yuyang Du
2014-07-11 2:01 ` Yuyang Du
2014-07-09 23:30 ` Yuyang Du
2014-07-10 17:06 ` bsegall
2014-07-10 20:08 ` Yuyang Du
2014-07-08 12:50 ` Peter Zijlstra
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