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 <[email protected]>
---
mm/swapfile.c | 14 ++++++++++++--
1 files changed, 12 insertions(+), 2 deletions(-)
--- swap10/mm/swapfile.c 2005-07-08 19:15:20.000000000 +0100
+++ swap11/mm/swapfile.c 2005-07-08 19:15:33.000000000 +0100
@@ -54,8 +54,6 @@ 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;
@@ -82,9 +80,13 @@ void swap_unplug_io_fn(struct backing_de
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
@@ -115,6 +117,10 @@ static inline unsigned long scan_swap_ma
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;
@@ -151,6 +157,10 @@ 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;
-
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