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authorWu Fengguang <fengguang.wu@intel.com>2009-09-23 21:56:00 +0800
committerJens Axboe <jens.axboe@oracle.com>2009-09-25 18:08:24 +0200
commit3a2e9a5a2afc1a2d2c548b8987f133235cebe933 (patch)
treecb05d2873b2701ded758a7087de5af2932a97736 /mm
parentfs: Fix busyloop in wb_writeback() (diff)
downloadlinux-dev-3a2e9a5a2afc1a2d2c548b8987f133235cebe933.tar.xz
linux-dev-3a2e9a5a2afc1a2d2c548b8987f133235cebe933.zip
writeback: balance_dirty_pages() shall write more than dirtied pages
Some filesystem may choose to write much more than ratelimit_pages before calling balance_dirty_pages_ratelimited_nr(). So it is safer to determine number to write based on real number of dirtied pages. Otherwise it is possible that loop { btrfs_file_write(): dirty 1024 pages balance_dirty_pages(): write up to 48 pages (= ratelimit_pages * 1.5) } in which the writeback rate cannot keep up with dirty rate, and the dirty pages go all the way beyond dirty_thresh. The increased write_chunk may make the dirtier more bumpy. So filesystems shall be take care not to dirty too much at a time (eg. > 4MB) without checking the ratelimit. Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'mm')
-rw-r--r--mm/page-writeback.c16
1 files changed, 10 insertions, 6 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 5f378dd58802..cbd4cba468bd 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -44,12 +44,15 @@ static long ratelimit_pages = 32;
/*
* When balance_dirty_pages decides that the caller needs to perform some
* non-background writeback, this is how many pages it will attempt to write.
- * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably
+ * It should be somewhat larger than dirtied pages to ensure that reasonably
* large amounts of I/O are submitted.
*/
-static inline long sync_writeback_pages(void)
+static inline long sync_writeback_pages(unsigned long dirtied)
{
- return ratelimit_pages + ratelimit_pages / 2;
+ if (dirtied < ratelimit_pages)
+ dirtied = ratelimit_pages;
+
+ return dirtied + dirtied / 2;
}
/* The following parameters are exported via /proc/sys/vm */
@@ -477,7 +480,8 @@ get_dirty_limits(unsigned long *pbackground, unsigned long *pdirty,
* If we're over `background_thresh' then pdflush is woken to perform some
* writeout.
*/
-static void balance_dirty_pages(struct address_space *mapping)
+static void balance_dirty_pages(struct address_space *mapping,
+ unsigned long write_chunk)
{
long nr_reclaimable, bdi_nr_reclaimable;
long nr_writeback, bdi_nr_writeback;
@@ -485,7 +489,6 @@ static void balance_dirty_pages(struct address_space *mapping)
unsigned long dirty_thresh;
unsigned long bdi_thresh;
unsigned long pages_written = 0;
- unsigned long write_chunk = sync_writeback_pages();
unsigned long pause = 1;
struct backing_dev_info *bdi = mapping->backing_dev_info;
@@ -640,9 +643,10 @@ void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
p = &__get_cpu_var(bdp_ratelimits);
*p += nr_pages_dirtied;
if (unlikely(*p >= ratelimit)) {
+ ratelimit = sync_writeback_pages(*p);
*p = 0;
preempt_enable();
- balance_dirty_pages(mapping);
+ balance_dirty_pages(mapping, ratelimit);
return;
}
preempt_enable();