Messages in this thread | | | Date | Wed, 21 Jul 2010 15:31:19 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH 4/8] vmscan: Do not writeback filesystem pages in direct reclaim |
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On Wed, Jul 21, 2010 at 04:28:44PM +0200, Johannes Weiner wrote: > 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@csn.ul.ie> > > Acked-by: Rik van Riel <riel@redhat.com> > > 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. >
Above this is
while (!list_empty(page_list)) { ... }
page_list should be empty and keep_locked is putting the pages on ret_pages already so I think it's ok.
> > + *nr_still_dirty = nr_dirty; > > count_vm_events(PGACTIVATE, pgactivate); > > return nr_reclaimed; > > } > > Otherwise, > Reviewed-by: Johannes Weiner <hannes@cmpxchg.org> >
Thanks!
-- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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