linux-kernel - Re: [Xen-devel] [PATCH] xen-blkback: fix memory leak when persistent grants are used

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Message-ID: <1390577782.13513.8.camel@kazak.uk.xensource.com>
Date:	Fri, 24 Jan 2014 15:36:22 +0000
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Matt Wilson <msw@...ux.com>
CC:	Matt Wilson <msw@...zon.com>, <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xen.org>, Matt Rushton <mrushton@...zon.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Anthony Liguori <aliguori@...zon.com>,
	Roger Pau Monné <roger.pau@...rix.com>
Subject: Re: [Xen-devel] [PATCH] xen-blkback: fix memory leak when
 persistent grants are used

On Fri, 2014-01-24 at 09:21 +0000, Ian Campbell wrote:
> On Thu, 2014-01-23 at 11:28 -0800, Matt Wilson wrote:
> > From: Matt Rushton <mrushton@...zon.com>
> > 
> > Currently shrink_free_pagepool() is called before the pages used for
> > persistent grants are released via free_persistent_gnts(). This
> > results in a memory leak when a VBD that uses persistent grants is
> > torn down.
> 
> This may well be the explanation for the memory leak I was observing on
> ARM last night. I'll give it a go and let you know.

Results are a bit inconclusive unfortunately, it seems like I am seeing
some other leak too (or instead).

Totally unscientifically it does seem to be leaking more slowly than
before, so perhaps this patch has helped, but nothing conclusive I'm
afraid.

I don't think that quite qualifies for a Tested-by though, sorry.

Ian. 

> 
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> > Cc: "Roger Pau Monné" <roger.pau@...rix.com>
> > Cc: Ian Campbell <Ian.Campbell@...rix.com>
> > Cc: David Vrabel <david.vrabel@...rix.com>
> > Cc: linux-kernel@...r.kernel.org
> > Cc: xen-devel@...ts.xen.org
> > Cc: Anthony Liguori <aliguori@...zon.com>
> > Signed-off-by: Matt Rushton <mrushton@...zon.com>
> > Signed-off-by: Matt Wilson <msw@...zon.com>
> > ---
> >  drivers/block/xen-blkback/blkback.c |    6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
> > index 6620b73..30ef7b3 100644
> > --- a/drivers/block/xen-blkback/blkback.c
> > +++ b/drivers/block/xen-blkback/blkback.c
> > @@ -625,9 +625,6 @@ purge_gnt_list:
> >  			print_stats(blkif);
> >  	}
> >  
> > -	/* Since we are shutting down remove all pages from the buffer */
> > -	shrink_free_pagepool(blkif, 0 /* All */);
> > -
> >  	/* Free all persistent grant pages */
> >  	if (!RB_EMPTY_ROOT(&blkif->persistent_gnts))
> >  		free_persistent_gnts(blkif, &blkif->persistent_gnts,
> > @@ -636,6 +633,9 @@ purge_gnt_list:
> >  	BUG_ON(!RB_EMPTY_ROOT(&blkif->persistent_gnts));
> >  	blkif->persistent_gnt_c = 0;
> >  
> > +	/* Since we are shutting down remove all pages from the buffer */
> > +	shrink_free_pagepool(blkif, 0 /* All */);
> > +
> >  	if (log_stats)
> >  		print_stats(blkif);
> >  
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xen.org
> http://lists.xen.org/xen-devel


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