linux-kernel - Re: [PATCH] sched: update_rq_clock() must skip ONE update

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Date:	Tue, 08 Apr 2014 18:56:02 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] sched: update_rq_clock() must skip ONE update

On Tue, 2014-04-08 at 17:53 +0200, Peter Zijlstra wrote:

> OK; so as previously mentioned (Oct '13); I've entirely had it with
> skip_clock_update bugs, so I got angry and did the below.

Goody, kick butt take names ;-)

> Its not something I can merge, not least because it uses trace_printk(),
> but it should be usable to 1) demonstate the above actually helps and 2)
> make damn sure we got it right this time :-)

That would be nice, little cycle savers like this aren't supposed to
have nasty corner cases that can clean your clock (pun intended).

> I've not really stared at the output much yet; but when you select
> function_graph tracer; we get lovely things like:

I'll plug it into my quilt pile.

-Mike


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