Tests show that btrfs is repeatedly moving _all_ PG_dirty pages into PG_writeback state. It's desirable to have some limit on the number of writeback pages. Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> --- fs/btrfs/disk-io.c | 7 +++++++ 1 file changed, 7 insertions(+) before patch: http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/btrfs-1dd-1M-8p-2952M-2.6.37-rc5+-2010-12-08-21-30/vmstat-dirty-300.png after patch: http://www.kernel.org/pub/linux/kernel/people/wfg/writeback/tests/3G/btrfs-1dd-1M-8p-2952M-2.6.37-rc5+-2010-12-08-21-14/vmstat-dirty-300.png --- linux-next.orig/fs/btrfs/disk-io.c 2011-03-03 14:03:39.000000000 +0800 +++ linux-next/fs/btrfs/disk-io.c 2011-03-03 14:03:40.000000000 +0800 @@ -616,6 +616,7 @@ int btrfs_wq_submit_bio(struct btrfs_fs_ extent_submit_bio_hook_t *submit_bio_done) { struct async_submit_bio *async; + int limit; async = kmalloc(sizeof(*async), GFP_NOFS); if (!async) @@ -643,6 +644,12 @@ int btrfs_wq_submit_bio(struct btrfs_fs_ btrfs_queue_worker(&fs_info->workers, &async->work); + limit = btrfs_async_submit_limit(fs_info); + + if (atomic_read(&fs_info->nr_async_bios) > limit) + wait_event(fs_info->async_submit_wait, + (atomic_read(&fs_info->nr_async_bios) < limit)); + while (atomic_read(&fs_info->async_submit_draining) && atomic_read(&fs_info->nr_async_submits)) { wait_event(fs_info->async_submit_wait, -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
