Date: Mon, 12 Nov 2012 13:31:39 +0000
From: Mel Gorman <mgorman@suse.de>
To: Zdenek Kabelac <zkabelac@redhat.com>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>, Jiri Slaby <jslaby@suse.cz>,
        Valdis.Kletnieks@vt.edu, Jiri Slaby <jirislaby@gmail.com>,
        linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Rik van Riel <riel@redhat.com>,
        Robert Jennings <rcj@linux.vnet.ibm.com>
Subject: Re: kswapd0: excessive CPU usage
Message-ID: <20121112133139.GU8218@suse.de>
References: <20121015110937.GE29125@suse.de>
 <5093A3F4.8090108@redhat.com>
 <5093A631.5020209@suse.cz>
 <509422C3.1000803@suse.cz>
 <509C84ED.8090605@linux.vnet.ibm.com>
 <509CB9D1.6060704@redhat.com>
 <20121109090635.GG8218@suse.de>
 <509F6C2A.9060502@redhat.com>
 <20121112121956.GT8218@suse.de>
 <50A0F5F0.6090400@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-15
Content-Disposition: inline
In-Reply-To: <50A0F5F0.6090400@redhat.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1948
Lines: 49

On Mon, Nov 12, 2012 at 02:13:20PM +0100, Zdenek Kabelac wrote:
> Dne 12.11.2012 13:19, Mel Gorman napsal(a):
> >On Sun, Nov 11, 2012 at 10:13:14AM +0100, Zdenek Kabelac wrote:
> >>Hmm,  so it's just took longer to hit the problem and observe kswapd0
> >>spinning on my CPU again - it's not as endless like before - but
> >>still it easily eats minutes - it helps to  turn off  Firefox or TB
> >>(memory hungry apps) so kswapd0 stops soon - and restart those apps
> >>again.
> >>(And I still have like >1GB of cached memory)
> >>
> >
> >I posted a "safe" patch that I believe explains why you are seeing what
> >you are seeing. It does mean that there will still be some stalls due to
> >THP because kswapd is not helping and it's avoiding the problem rather
> >than trying to deal with it.
> >
> >Hence, I'm also going to post this patch even though I have not tested
> >it myself. If you find it fixes the problem then it would be a
> >preferable patch to the revert. It still is the case that the
> >balance_pgdat() logic is in sort need of a rethink as it's pretty
> >twisted right now.
> >
> 
> 
> Should I apply them all together for 3.7-rc5 ?
> 
> 1) https://lkml.org/lkml/2012/11/5/308
> 2) https://lkml.org/lkml/2012/11/12/113
> 3) https://lkml.org/lkml/2012/11/12/151
> 

Not all together. Test either 1+2 or 1+3. 1+2 is the safer choice but
does nothing about THP stalls. 1+3 is a riskier version but depends on
me being correct on what the root cause of the problem you see it.

If both 1+2 and 1+3 work for you, I'd choose 1+3 for merging. If you only
have the time to test one combination then it would be preferred that you
test the safe option of 1+2.

Thanks.

-- 
Mel Gorman
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/