linux-kernel - Re: [PATCH]sched_rt.c: Avoid unnecessary dequeue and enqueue of pushable tasks in set_cpus_allowed

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Message-ID: <1334066322.23924.204.camel@gandalf.stny.rr.com>
Date:	Tue, 10 Apr 2012 09:58:42 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Kirill Tkhai <tkhai@...dex.ru>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH]sched_rt.c: Avoid unnecessary dequeue and enqueue of
 pushable tasks in set_cpus_allowed_rt()

On Sat, 2012-03-17 at 03:58 +0400, Kirill Tkhai wrote:
> Steven, what is about the patch from my previous message? Is everything ok?

You're timing is impeccable. I was in Chemnitz, Germany when you sent
this, and it too was lost in the noise ;-)

I'll take a look at it today.

Thanks!

-- Steve

 
> 
> Regards,
> Kirill
> 
> 19.02.2012, 18:17, "Kirill Tkhai" <tkhai@...dex.ru>:
> > 13.02.2012, 21:23, "Steven Rostedt" <rostedt@...dmis.org>:
> >
> >>  I wasn't on the Cc of the original message, but it was bounced to me
> >>  awhile ago. I'm cleaning out my email and came across it.
> >>
> >>  Can you send me the latest version of this patch, either against latest
> >>  Linus, or against tip/master.
> >>
> >>  Thanks,
> >>
> >>  -- Steve
> >>
> >>  P.S. I'll be at ELC this week so it may not get processed right away.
> >
> > Migration status depends on a difference of weight from 0 and 1.
> > If weight > 1 (<= 1) and old weight <= 1 (> 1) then task becomes
> > pushable (or not pushable). We are not insterested in its exact
> > values, is it 3 or 4, for example.
> >
> > Now if we are changing affinity from a set of 3 cpus to a set of 4, the-
> > task will be dequeued and enqueued sequentially without important
> > difference in comparison with initial state. The only difference is in
> > internal representation of plist queue of pushable tasks and the fact
> > that the task may won't be the first in a sequence of the same priority
> > tasks. But it seems to me it gives nothing.
> >
> > Signed-off-by: Tkhai Kirill <tkhai@...dex.ru>


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