From 43ff2122e6492bcc88b065c433453dce88223b30 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Mon, 23 Apr 2012 15:58:39 +1000 Subject: xfs: on-stack delayed write buffer lists Queue delwri buffers on a local on-stack list instead of a per-buftarg one, and write back the buffers per-process instead of by waking up xfsbufd. This is now easily doable given that we have very few places left that write delwri buffers: - log recovery: Only done at mount time, and already forcing out the buffers synchronously using xfs_flush_buftarg - quotacheck: Same story. - dquot reclaim: Writes out dirty dquots on the LRU under memory pressure. We might want to look into doing more of this via xfsaild, but it's already more optimal than the synchronous inode reclaim that writes each buffer synchronously. - xfsaild: This is the main beneficiary of the change. By keeping a local list of buffers to write we reduce latency of writing out buffers, and more importably we can remove all the delwri list promotions which were hitting the buffer cache hard under sustained metadata loads. The implementation is very straight forward - xfs_buf_delwri_queue now gets a new list_head pointer that it adds the delwri buffers to, and all callers need to eventually submit the list using xfs_buf_delwi_submit or xfs_buf_delwi_submit_nowait. Buffers that already are on a delwri list are skipped in xfs_buf_delwri_queue, assuming they already are on another delwri list. The biggest change to pass down the buffer list was done to the AIL pushing. Now that we operate on buffers the trylock, push and pushbuf log item methods are merged into a single push routine, which tries to lock the item, and if possible add the buffer that needs writeback to the buffer list. This leads to much simpler code than the previous split but requires the individual IOP_PUSH instances to unlock and reacquire the AIL around calls to blocking routines. Given that xfsailds now also handle writing out buffers, the conditions for log forcing and the sleep times needed some small changes. The most important one is that we consider an AIL busy as long we still have buffers to push, and the other one is that we do increment the pushed LSN for buffers that are under flushing at this moment, but still count them towards the stuck items for restart purposes. Without this we could hammer on stuck items without ever forcing the log and not make progress under heavy random delete workloads on fast flash storage devices. [ Dave Chinner: - rebase on previous patches. - improved comments for XBF_DELWRI_Q handling - fix XBF_ASYNC handling in queue submission (test 106 failure) - rename delwri submit function buffer list parameters for clarity - xfs_efd_item_push() should return XFS_ITEM_PINNED ] Signed-off-by: Christoph Hellwig Reviewed-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_sync.c | 18 ------------------ 1 file changed, 18 deletions(-) (limited to 'fs/xfs/xfs_sync.c') diff --git a/fs/xfs/xfs_sync.c b/fs/xfs/xfs_sync.c index 468c3c0..cdb644f 100644 --- a/fs/xfs/xfs_sync.c +++ b/fs/xfs/xfs_sync.c @@ -313,17 +313,10 @@ xfs_quiesce_data( /* write superblock and hoover up shutdown errors */ error = xfs_sync_fsdata(mp); - /* make sure all delwri buffers are written out */ - xfs_flush_buftarg(mp->m_ddev_targp, 1); - /* mark the log as covered if needed */ if (xfs_log_need_covered(mp)) error2 = xfs_fs_log_dummy(mp); - /* flush data-only devices */ - if (mp->m_rtdev_targp) - xfs_flush_buftarg(mp->m_rtdev_targp, 1); - return error ? error : error2; } @@ -684,17 +677,6 @@ restart: if (!xfs_iflock_nowait(ip)) { if (!(sync_mode & SYNC_WAIT)) goto out; - - /* - * If we only have a single dirty inode in a cluster there is - * a fair chance that the AIL push may have pushed it into - * the buffer, but xfsbufd won't touch it until 30 seconds - * from now, and thus we will lock up here. - * - * Promote the inode buffer to the front of the delwri list - * and wake up xfsbufd now. - */ - xfs_promote_inode(ip); xfs_iflock(ip); } -- cgit v1.1