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authorHugh Dickins <hugh@veritas.com>2005-09-03 18:54:40 -0400
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 03:05:41 -0400
commit048c27fd72816b44e096997d1c6901c3abbfd45b (patch)
tree159a00b71ce9db161a48e4fc07b212db455a2cf1
parent52b7efdbe5f5696fc80338560a3fc51e0b0a993c (diff)
[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>
-rw-r--r--mm/swapfile.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index fdee145afc6f..e675ae55f87d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -56,8 +56,6 @@ static DECLARE_MUTEX(swapon_sem);
56 */ 56 */
57static DECLARE_RWSEM(swap_unplug_sem); 57static DECLARE_RWSEM(swap_unplug_sem);
58 58
59#define SWAPFILE_CLUSTER 256
60
61void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page) 59void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
62{ 60{
63 swp_entry_t entry; 61 swp_entry_t entry;
@@ -84,9 +82,13 @@ void swap_unplug_io_fn(struct backing_dev_info *unused_bdi, struct page *page)
84 up_read(&swap_unplug_sem); 82 up_read(&swap_unplug_sem);
85} 83}
86 84
85#define SWAPFILE_CLUSTER 256
86#define LATENCY_LIMIT 256
87
87static inline unsigned long scan_swap_map(struct swap_info_struct *si) 88static inline unsigned long scan_swap_map(struct swap_info_struct *si)
88{ 89{
89 unsigned long offset, last_in_cluster; 90 unsigned long offset, last_in_cluster;
91 int latency_ration = LATENCY_LIMIT;
90 92
91 /* 93 /*
92 * We try to cluster swap pages by allocating them sequentially 94 * 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)
117 si->cluster_next = offset-SWAPFILE_CLUSTER-1; 119 si->cluster_next = offset-SWAPFILE_CLUSTER-1;
118 goto cluster; 120 goto cluster;
119 } 121 }
122 if (unlikely(--latency_ration < 0)) {
123 cond_resched();
124 latency_ration = LATENCY_LIMIT;
125 }
120 } 126 }
121 swap_device_lock(si); 127 swap_device_lock(si);
122 goto lowest; 128 goto lowest;
@@ -153,6 +159,10 @@ checks: if (!(si->flags & SWP_WRITEOK))
153 swap_device_lock(si); 159 swap_device_lock(si);
154 goto checks; 160 goto checks;
155 } 161 }
162 if (unlikely(--latency_ration < 0)) {
163 cond_resched();
164 latency_ration = LATENCY_LIMIT;
165 }
156 } 166 }
157 swap_device_lock(si); 167 swap_device_lock(si);
158 goto lowest; 168 goto lowest;