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: 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>
diff --git a/mm/vmscan.c b/mm/vmscan.c
index a1893c0..f525544 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -247,14 +247,18 @@
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 @@
} 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);