From 635697c663f38106063d5659f0cf2e45afcd4bb5 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Thu, 8 Dec 2011 14:33:51 -0800 Subject: 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 Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index a1893c050795..f5255442ae2b 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -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); -- cgit v1.2.3 From 83aeeada7c69f35e5100b27ec354335597a7a488 Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Thu, 8 Dec 2011 14:33:54 -0800 Subject: vmscan: use atomic-long for shrinker batching Use atomic-long operations instead of looping around cmpxchg(). [akpm@linux-foundation.org: massage atomic.h inclusions] Signed-off-by: Konstantin Khlebnikov Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/fs.h | 2 +- include/linux/mm.h | 1 + include/linux/shrinker.h | 2 +- mm/vmscan.c | 17 +++++++---------- 4 files changed, 10 insertions(+), 12 deletions(-) (limited to 'mm/vmscan.c') diff --git a/include/linux/fs.h b/include/linux/fs.h index 019dc558df1a..e0bc4ffb8e7f 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -393,8 +393,8 @@ struct inodes_stat_t { #include #include #include -#include #include +#include #include diff --git a/include/linux/mm.h b/include/linux/mm.h index 3dc3a8c2c485..4baadd18f4ad 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index a83833a1f7a2..07ceb97d53fa 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -35,7 +35,7 @@ struct shrinker { /* These are for internal use */ struct list_head list; - long nr; /* objs pending delete */ + atomic_long_t nr_in_batch; /* objs pending delete */ }; #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */ extern void register_shrinker(struct shrinker *); diff --git a/mm/vmscan.c b/mm/vmscan.c index f5255442ae2b..f54a05b7a61d 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -183,7 +183,7 @@ static unsigned long zone_nr_lru_pages(struct zone *zone, */ void register_shrinker(struct shrinker *shrinker) { - shrinker->nr = 0; + atomic_long_set(&shrinker->nr_in_batch, 0); down_write(&shrinker_rwsem); list_add_tail(&shrinker->list, &shrinker_list); up_write(&shrinker_rwsem); @@ -264,9 +264,7 @@ unsigned long shrink_slab(struct shrink_control *shrink, * and zero it so that other concurrent shrinker invocations * don't also do this scanning work. */ - do { - nr = shrinker->nr; - } while (cmpxchg(&shrinker->nr, nr, 0) != nr); + nr = atomic_long_xchg(&shrinker->nr_in_batch, 0); total_scan = nr; delta = (4 * nr_pages_scanned) / shrinker->seeks; @@ -328,12 +326,11 @@ unsigned long shrink_slab(struct shrink_control *shrink, * manner that handles concurrent updates. If we exhausted the * scan, there is no need to do an update. */ - do { - nr = shrinker->nr; - new_nr = total_scan + nr; - if (total_scan <= 0) - break; - } while (cmpxchg(&shrinker->nr, nr, new_nr) != nr); + if (total_scan > 0) + new_nr = atomic_long_add_return(total_scan, + &shrinker->nr_in_batch); + else + new_nr = atomic_long_read(&shrinker->nr_in_batch); trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); } -- cgit v1.2.3