Messages in this thread |  | | | Date | Mon, 19 Jul 2010 14:25:42 -0400 | | From | Rik van Riel <> | | Subject | Re: [PATCH 4/8] vmscan: Do not writeback filesystem pages in direct reclaim |
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On 07/19/2010 09:11 AM, Mel Gorman wrote: > When memory is under enough pressure, a process may enter direct > reclaim to free pages in the same manner kswapd does. If a dirty page is > encountered during the scan, this page is written to backing storage using > mapping->writepage. This can result in very deep call stacks, particularly > if the target storage or filesystem are complex. It has already been observed > on XFS that the stack overflows but the problem is not XFS-specific. > > This patch prevents direct reclaim writing back filesystem pages by checking > if current is kswapd or the page is anonymous before writing back. If the > dirty pages cannot be written back, they are placed back on the LRU lists > for either background writing by the BDI threads or kswapd. If in direct > lumpy reclaim and dirty pages are encountered, the process will stall for > the background flusher before trying to reclaim the pages again. > > 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. > > Signed-off-by: Mel Gorman<mel@csn.ul.ie>
Acked-by: Rik van Riel <riel@redhat.com>
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