On Wed, Jul 21, 2010 at 02:38:57PM +0100, Mel Gorman wrote: > Here is an updated version. Thanks very much > > ==== CUT HERE ==== > vmscan: Do not writeback filesystem pages in direct reclaim > > 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@xxxxxxxxx> > Acked-by: Rik van Riel <riel@xxxxxxxxxx> Cool! Except for one last tiny thing... > @@ -858,7 +872,7 @@ keep: > > free_page_list(&free_pages); > > - list_splice(&ret_pages, page_list); This will lose all retry pages forever, I think. > + *nr_still_dirty = nr_dirty; > count_vm_events(PGACTIVATE, pgactivate); > return nr_reclaimed; > } Otherwise, Reviewed-by: Johannes Weiner <hannes@xxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>