On Thu, 2012-07-26 at 14:29 -0700, Greg Kroah-Hartman wrote: > From: Greg KH <gre...@linuxfoundation.org> > > 3.0-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Dave Chinner <dchin...@redhat.com> > > commit acf92b485cccf028177f46918e045c0c4e80ee10 upstream. > > Stable note: Not tracked in Bugzilla. This patch reduces excessive > reclaim of slab objects reducing the amount of information > that has to be brought back in from disk. > > shrink_slab() allows shrinkers to be called in parallel so the > struct shrinker can be updated concurrently. It does not provide any > exclusio for such updates, so we can get the shrinker->nr value > increasing or decreasing incorrectly. > > As a result, when a shrinker repeatedly returns a value of -1 (e.g. > a VFS shrinker called w/ GFP_NOFS), the shrinker->nr goes haywire, > sometimes updating with the scan count that wasn't used, sometimes > losing it altogether. Worse is when a shrinker does work and that > update is lost due to racy updates, which means the shrinker will do > the work again! > > Fix this by making the total_scan calculations independent of > shrinker->nr, and making the shrinker->nr updates atomic w.r.t. to > other updates via cmpxchg loops. [...] > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -251,17 +251,29 @@ unsigned long shrink_slab(struct shrink_ > unsigned long total_scan; [...] > + total_scan += delta; > + if (total_scan < 0) { [...]
This condition is never true since total_scan is unsigned. I think 3.0.y needs this as well: commit 635697c663f38106063d5659f0cf2e45afcd4bb5 Author: Konstantin Khlebnikov <khlebni...@openvz.org> Date: Thu Dec 8 14:33:51 2011 -0800 vmscan: fix initial shrinker size handling Ben. -- Ben Hutchings Man invented language to satisfy his deep need to complain. - Lily Tomlin
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