Messages in this thread | | | Date | Mon, 19 Jul 2010 15:26:22 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 4/8] vmscan: Do not writeback filesystem pages in direct reclaim |
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On Mon, Jul 19, 2010 at 10:19:34AM -0400, Christoph Hellwig wrote: > On Mon, Jul 19, 2010 at 02:11:26PM +0100, Mel Gorman wrote: > > As the call-chain for writing anonymous pages is not expected to be deep > > and they are not cleaned by flusher threads, anonymous pages are still > > written back in direct reclaim. > > While it is not quite as deep as it skips the filesystem allocator and > extent mapping code it can still be quite deep for swap given that it > still has to traverse the whole I/O stack. Probably not worth worrying > about now, but we need to keep an eye on it. >
Agreed that we need to keep an eye on it. If this ever becomes a problem, we're going to need to consider a flusher for anonymous pages. If you look at the figures, we are still doing a lot of writeback of anonymous pages. Granted, the layout of swap sucks anyway but it's something to keep at the back of the mind.
> The patch looks fine to me anyway. >
Thanks.
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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