vmscan: fix initial shrinker size handling (635697c6) · Commits · 戴 / test

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 <khlebnikov@openvz.org> Cc: Dave Chinner <david@fromorbit.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

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);

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