Date: Fri, 11 Jun 2010 12:25:23 -0400
From: Christoph Hellwig <hch@infradead.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Mel Gorman <mel@csn.ul.ie>, linux-kernel@vger.kernel.org,
       linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
       Dave Chinner <david@fromorbit.com>,
       Chris Mason <chris.mason@oracle.com>, Nick Piggin <npiggin@suse.de>,
       Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 6/6] vmscan: Do not writeback pages in direct reclaim
Message-ID: <20100611162523.GA24707@infradead.org>
References: <1275987745-21708-1-git-send-email-mel@csn.ul.ie>
 <1275987745-21708-7-git-send-email-mel@csn.ul.ie>
 <20100610231706.1d7528f2.akpm@linux-foundation.org>
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On Thu, Jun 10, 2010 at 11:17:06PM -0700, Andrew Morton wrote:
> As it stands, it would be wildly incautious to make a change like
> this without first working out why we're pulling so many dirty pages
> off the LRU tail, and fixing that.

Note that unlike the writepage vs writepages from kswapd which can
be fixed by the right tuning this is a black or white issue.  Writeback
from direct reclaim will kill your stack if the caller happens to be
the wrong one, and just making it happen less often is not a fix - it
must not happen at all.

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