linux-kernel - Re: [PATCH 2/3] sched,fair: Fix local starvation

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Date:	Sun, 22 May 2016 09:15:34 +0200
From:	Mike Galbraith <mgalbraith@...e.de>
To:	Wanpeng Li <kernellwp@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Pavan Kondeti <pkondeti@...eaurora.org>,
	Ben Segall <bsegall@...gle.com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Paul Turner <pjt@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Byungchul Park <byungchul.park@....com>,
	Andrew Hunter <ahh@...gle.com>
Subject: Re: [PATCH 2/3] sched,fair: Fix local starvation

On Sun, 2016-05-22 at 14:50 +0800, Wanpeng Li wrote:
> 2016-05-21 22:04 GMT+08:00 Mike Galbraith <mgalbraith@...e.de>:
> > On Tue, 2016-05-10 at 19:43 +0200, Peter Zijlstra wrote:
> > 
> > (Evolution authors must either not do patch review, or use some other
> > mailer.  Squint hard, this crud really is your patch;)
> > 
> > > --- a/kernel/sched/core.c
> > > +++ b/kernel/sched/core.c
> > > 
> > > @@ -1762,7 +1770,11 @@ void sched_ttwu_pending(void)
> > >  >    > while (llist) {
> > >  >    >       > p = llist_entry(llist, struct task_struct, wake_entry);
> > >  >    >       > llist = llist_next(llist);
> > > ->    >       > ttwu_do_activate(rq, p, 0, cookie);
> > > +>    >       > /*
> > > +>    >       >  * See ttwu_queue(); we only call ttwu_queue_remote() when
> > > +>    >       >  * its a x-cpu wakeup.
> > > +>    >       >  */
> > > +>    >       > ttwu_do_activate(rq, p, WF_MIGRATED, cookie);
> > 
> > Wakees that were not migrated/normalized eat an unwanted min_vruntime,
> 
> Why there were wakees queued by twu_queue_remote() not migrated?

Queuing to a remote cache domain implies x-cpu wakeup, but does not
imply migration.

	-Mike