linux-kernel - Re: [PATCH v8 1/5] mm: introduce a common interface for balloon pages mobility

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Message-ID: <20120823161026.GA29059@redhat.com>
Date:	Thu, 23 Aug 2012 19:10:26 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Rafael Aquini <aquini@...hat.com>
Cc:	Rik van Riel <riel@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mel Gorman <mel@....ul.ie>, Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Minchan Kim <minchan@...nel.org>
Subject: Re: [PATCH v8 1/5] mm: introduce a common interface for balloon
 pages mobility

On Thu, Aug 23, 2012 at 01:06:48PM -0300, Rafael Aquini wrote:
> On Thu, Aug 23, 2012 at 12:03:15PM -0400, Rik van Riel wrote:
> > >
> > >Not "longer" - apparently forever unless user resend the leak command.
> > >It's wrong - it should
> > >1. not tell host if nothing was done
> > >2. after migration finished leak and tell host
> > 
> > Agreed.  If the balloon is told to leak N pages, and could
> > not do so because those pages were locked, the balloon driver
> > needs to retry (maybe waiting on a page lock?) and not signal
> > completion until after the job has been completed.
> > 
> > Having the balloon driver wait on the page lock should be
> > fine, because compaction does not hold the page lock for
> > long.
> 
> And that is precisely what leak_balloon is doing. When it stumbles across a
> locked page it gets rid of that leak round to give a shot for compaction to
> finish its task.
> 

Yes but I do not see where it will retry.
If it does, please add a comment pointing out where it happens.

-- 
MST
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