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authorHugh Dickins <hugh@veritas.com>2005-09-03 15:54:40 -0700
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 00:05:41 -0700
commit048c27fd72816b44e096997d1c6901c3abbfd45b (patch)
tree159a00b71ce9db161a48e4fc07b212db455a2cf1 /mm/swapfile.c
parent52b7efdbe5f5696fc80338560a3fc51e0b0a993c (diff)
downloadlinux-linaro-048c27fd72816b44e096997d1c6901c3abbfd45b.tar.gz
[PATCH] swap: scan_swap_map latency breaks
The get_swap_page/scan_swap_map latency can be so bad that even those without preemption configured deserve relief: periodically cond_resched. Signed-off-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/swapfile.c')
-rw-r--r--mm/swapfile.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index fdee145afc6..e675ae55f87 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -56,8 +56,6 @@ static DECLARE_MUTEX(swapon_sem);
*/
static DECLARE_RWSEM(swap_unplug_sem);
-#define SWAPFILE_CLUSTER 256
-
void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
{
swp_entry_t entry;
@@ -84,9 +82,13 @@ void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
up_read(&swap_unplug_sem);
}
+#define SWAPFILE_CLUSTER 256
+#define LATENCY_LIMIT 256
+
static inline unsigned long scan_swap_map(struct swap_info_struct *si)
{
unsigned long offset, last_in_cluster;
+ int latency_ration = LATENCY_LIMIT;
/*
* We try to cluster swap pages by allocating them sequentially
@@ -117,6 +119,10 @@ static inline unsigned long scan_swap_map(struct swap_info_struct *si)
si->cluster_next = offset-SWAPFILE_CLUSTER-1;
goto cluster;
}
+ if (unlikely(--latency_ration < 0)) {
+ cond_resched();
+ latency_ration = LATENCY_LIMIT;
+ }
}
swap_device_lock(si);
goto lowest;
@@ -153,6 +159,10 @@ checks: if (!(si->flags & SWP_WRITEOK))
swap_device_lock(si);
goto checks;
}
+ if (unlikely(--latency_ration < 0)) {
+ cond_resched();
+ latency_ration = LATENCY_LIMIT;
+ }
}
swap_device_lock(si);
goto lowest;