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Commit 635697c6 authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Linus Torvalds
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vmscan: fix initial shrinker size handling 



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: default avatarKonstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 09d9673d

mm/vmscan.c

+6 −3
Original line number Diff line number Diff line
@@ -247,14 +247,18 @@ 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;

		long batch_size = shrinker->batch ? shrinker->batch

						  : SHRINK_BATCH;



		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
@@ -265,7 +269,6 @@ 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);