On Sun, Jul 29, 2012 at 09:29:30PM +0100, Ben Hutchings wrote: > > --- 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 >
You're right, thanks for pointing it out as I missed it. Greg, this commit is already in 3.2 but can you pick it up for 3.0-stable please? ---8<--- vmscan: fix initial shrinker size handling commit 635697c663f38106063d5659f0cf2e45afcd4bb5 upstream. Stable note: The commit [acf92b48: vmscan: shrinker->nr updates race and go wrong] aimed to reduce excessive reclaim of slab objects but had bug in how it treated shrinker functions that returned -1. A shrinker function can return -1, means that it cannot do anything without a risk of deadlock. For example prune_super() does this if it cannot grab a superblock refrence, even if nr_to_scan=0. Currently we interpret this -1 as a ULONG_MAX size shrinker and evaluate `total_scan' according to this. So the next time around this shrinker can cause really big pressure. Let's skip such shrinkers instead. Also make total_scan signed, otherwise the check (total_scan < 0) below never works. Signed-off-by: Konstantin Khlebnikov <khlebni...@openvz.org> Cc: Dave Chinner <da...@fromorbit.com> Signed-off-by: Andrew Morton <a...@linux-foundation.org> Signed-off-by: Linus Torvalds <torva...@linux-foundation.org> Signed-off-by: Mel Gorman <mgor...@suse.de> --- mm/vmscan.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index e0afff3..bd8a540 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -248,12 +248,16 @@ unsigned long shrink_slab(struct shrink_control *shrink, list_for_each_entry(shrinker, &shrinker_list, list) { unsigned long long delta; - unsigned long total_scan; - unsigned long max_pass; + long total_scan; + long max_pass; int shrink_ret = 0; long nr; long new_nr; + max_pass = do_shrinker_shrink(shrinker, shrink, 0); + if (max_pass <= 0) + continue; + /* * copy the current shrinker scan count into a local variable * and zero it so that other concurrent shrinker invocations @@ -264,7 +268,6 @@ unsigned long shrink_slab(struct shrink_control *shrink, } while (cmpxchg(&shrinker->nr, nr, 0) != nr); total_scan = nr; - max_pass = do_shrinker_shrink(shrinker, shrink, 0); delta = (4 * nr_pages_scanned) / shrinker->seeks; delta *= max_pass; do_div(delta, lru_pages + 1); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/