From: Brian Foster <bfoster@redhat.com> To: Dave Chinner <david@fromorbit.com> Cc: linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 07/26] xfs: tail updates only need to occur when LSN changes Date: Fri, 11 Oct 2019 08:40:43 -0400 Message-ID: <20191011124043.GG61257@bfoster> (raw) In-Reply-To: <20191009032124.10541-8-david@fromorbit.com> On Wed, Oct 09, 2019 at 02:21:05PM +1100, Dave Chinner wrote: > From: Dave Chinner <dchinner@redhat.com> > > We currently wake anything waiting on the log tail to move whenever > the log item at the tail of the log is removed. Historically this > was fine behaviour because there were very few items at any given > LSN. But with delayed logging, there may be thousands of items at > any given LSN, and we can't move the tail until they are all gone. > > Hence if we are removing them in near tail-first order, we might be > waking up processes waiting on the tail LSN to change (e.g. log > space waiters) repeatedly without them being able to make progress. > This also occurs with the new sync push waiters, and can result in > thousands of spurious wakeups every second when under heavy direct > reclaim pressure. > > To fix this, check that the tail LSN has actually changed on the > AIL before triggering wakeups. This will reduce the number of > spurious wakeups when doing bulk AIL removal and make this code much > more efficient. > > Signed-off-by: Dave Chinner <dchinner@redhat.com> > --- > fs/xfs/xfs_inode_item.c | 18 ++++++++++---- > fs/xfs/xfs_trans_ail.c | 52 ++++++++++++++++++++++++++++------------- > fs/xfs/xfs_trans_priv.h | 4 ++-- > 3 files changed, 51 insertions(+), 23 deletions(-) > ... > diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c > index 656819523bbd..685a21cd24c0 100644 > --- a/fs/xfs/xfs_trans_ail.c > +++ b/fs/xfs/xfs_trans_ail.c ... > @@ -745,9 +754,10 @@ xfs_trans_ail_update_bulk( > continue; > > trace_xfs_ail_move(lip, lip->li_lsn, lsn); > + if (mlip == lip && !tail_lsn) > + tail_lsn = lip->li_lsn; > + > xfs_ail_delete(ailp, lip); > - if (mlip == lip) > - mlip_changed = 1; FWIW, I think this code could be simplified to just assign tail_lsn directly via the new helper and pass that value into xfs_ail_update_finish() below. I doubt filtering out that extra lsn comparison with the mlip check makes much difference when we're already doing a bulk insertion and referencing every lip along the way. That's just a nit though. Otherwise looks fine to me: Reviewed-by: Brian Foster <bfoster@redhat.com> > } else { > trace_xfs_ail_insert(lip, 0, lsn); > } > @@ -758,15 +768,23 @@ xfs_trans_ail_update_bulk( > if (!list_empty(&tmp)) > xfs_ail_splice(ailp, cur, &tmp, lsn); > > - xfs_ail_update_finish(ailp, mlip_changed); > + xfs_ail_update_finish(ailp, tail_lsn); > } > > -bool > +/* > + * Delete one log item from the AIL. > + * > + * If this item was at the tail of the AIL, return the LSN of the log item so > + * that we can use it to check if the LSN of the tail of the log has moved > + * when finishing up the AIL delete process in xfs_ail_update_finish(). > + */ > +xfs_lsn_t > xfs_ail_delete_one( > struct xfs_ail *ailp, > struct xfs_log_item *lip) > { > struct xfs_log_item *mlip = xfs_ail_min(ailp); > + xfs_lsn_t lsn = lip->li_lsn; > > trace_xfs_ail_delete(lip, mlip->li_lsn, lip->li_lsn); > xfs_ail_delete(ailp, lip); > @@ -774,7 +792,9 @@ xfs_ail_delete_one( > clear_bit(XFS_LI_IN_AIL, &lip->li_flags); > lip->li_lsn = 0; > > - return mlip == lip; > + if (mlip == lip) > + return lsn; > + return 0; > } > > /** > @@ -805,7 +825,7 @@ xfs_trans_ail_delete( > int shutdown_type) > { > struct xfs_mount *mp = ailp->ail_mount; > - bool need_update; > + xfs_lsn_t tail_lsn; > > if (!test_bit(XFS_LI_IN_AIL, &lip->li_flags)) { > spin_unlock(&ailp->ail_lock); > @@ -818,8 +838,8 @@ xfs_trans_ail_delete( > return; > } > > - need_update = xfs_ail_delete_one(ailp, lip); > - xfs_ail_update_finish(ailp, need_update); > + tail_lsn = xfs_ail_delete_one(ailp, lip); > + xfs_ail_update_finish(ailp, tail_lsn); > } > > int > diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h > index 64ffa746730e..35655eac01a6 100644 > --- a/fs/xfs/xfs_trans_priv.h > +++ b/fs/xfs/xfs_trans_priv.h > @@ -91,8 +91,8 @@ xfs_trans_ail_update( > xfs_trans_ail_update_bulk(ailp, NULL, &lip, 1, lsn); > } > > -bool xfs_ail_delete_one(struct xfs_ail *ailp, struct xfs_log_item *lip); > -void xfs_ail_update_finish(struct xfs_ail *ailp, bool do_tail_update) > +xfs_lsn_t xfs_ail_delete_one(struct xfs_ail *ailp, struct xfs_log_item *lip); > +void xfs_ail_update_finish(struct xfs_ail *ailp, xfs_lsn_t old_lsn) > __releases(ailp->ail_lock); > void xfs_trans_ail_delete(struct xfs_ail *ailp, struct xfs_log_item *lip, > int shutdown_type); > -- > 2.23.0.rc1 >
next prev parent reply index Thread overview: 87+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-10-09 3:20 [PATCH V2 00/26] mm, xfs: non-blocking inode reclaim Dave Chinner 2019-10-09 3:20 ` [PATCH 01/26] xfs: Lower CIL flush limit for large logs Dave Chinner 2019-10-11 12:39 ` Brian Foster 2019-10-30 17:08 ` Darrick J. Wong 2019-10-09 3:21 ` [PATCH 02/26] xfs: Throttle commits on delayed background CIL push Dave Chinner 2019-10-11 12:38 ` Brian Foster 2019-10-09 3:21 ` [PATCH 03/26] xfs: don't allow log IO to be throttled Dave Chinner 2019-10-11 9:35 ` Christoph Hellwig 2019-10-11 12:39 ` Brian Foster 2019-10-30 17:14 ` Darrick J. Wong 2019-10-09 3:21 ` [PATCH 04/26] xfs: Improve metadata buffer reclaim accountability Dave Chinner 2019-10-11 12:39 ` Brian Foster 2019-10-11 12:57 ` Christoph Hellwig 2019-10-11 23:14 ` Dave Chinner 2019-10-11 23:13 ` Dave Chinner 2019-10-12 12:05 ` Brian Foster 2019-10-13 3:14 ` Dave Chinner 2019-10-14 13:05 ` Brian Foster 2019-10-30 17:25 ` Darrick J. Wong 2019-10-30 21:43 ` Dave Chinner 2019-10-31 3:06 ` Darrick J. Wong 2019-10-31 20:50 ` Dave Chinner 2019-10-31 21:05 ` Darrick J. Wong 2019-10-31 21:22 ` Christoph Hellwig 2019-11-03 21:26 ` Dave Chinner 2019-11-04 23:08 ` Darrick J. Wong 2019-10-09 3:21 ` [PATCH 05/26] xfs: correctly acount for reclaimable slabs Dave Chinner 2019-10-11 12:39 ` Brian Foster 2019-10-30 17:16 ` Darrick J. Wong 2019-10-09 3:21 ` [PATCH 06/26] xfs: synchronous AIL pushing Dave Chinner 2019-10-11 9:42 ` Christoph Hellwig 2019-10-11 12:40 ` Brian Foster 2019-10-11 23:15 ` Dave Chinner 2019-10-09 3:21 ` [PATCH 07/26] xfs: tail updates only need to occur when LSN changes Dave Chinner 2019-10-11 9:50 ` Christoph Hellwig 2019-10-11 12:40 ` Brian Foster [this message] 2019-10-09 3:21 ` [PATCH 08/26] mm: directed shrinker work deferral Dave Chinner 2019-10-14 8:46 ` Christoph Hellwig 2019-10-14 13:06 ` Brian Foster 2019-10-18 7:59 ` Dave Chinner 2019-10-09 3:21 ` [PATCH 09/26] shrinkers: use defer_work for GFP_NOFS sensitive shrinkers Dave Chinner 2019-10-09 3:21 ` [PATCH 10/26] mm: factor shrinker work calculations Dave Chinner 2019-10-09 3:21 ` [PATCH 11/26] shrinker: defer work only to kswapd Dave Chinner 2019-10-09 3:21 ` [PATCH 12/26] shrinker: clean up variable types and tracepoints Dave Chinner 2019-10-09 3:21 ` [PATCH 13/26] mm: reclaim_state records pages reclaimed, not slabs Dave Chinner 2019-10-09 3:21 ` [PATCH 14/26] mm: back off direct reclaim on excessive shrinker deferral Dave Chinner 2019-10-11 16:21 ` Matthew Wilcox 2019-10-11 23:20 ` Dave Chinner 2019-10-09 3:21 ` [PATCH 15/26] mm: kswapd backoff for shrinkers Dave Chinner 2019-10-09 3:21 ` [PATCH 16/26] xfs: synchronous AIL pushing Dave Chinner 2019-10-11 10:18 ` Christoph Hellwig 2019-10-11 15:29 ` Brian Foster 2019-10-11 23:27 ` Dave Chinner 2019-10-12 12:08 ` Brian Foster 2019-10-09 3:21 ` [PATCH 17/26] xfs: don't block kswapd in inode reclaim Dave Chinner 2019-10-11 15:29 ` Brian Foster 2019-10-09 3:21 ` [PATCH 18/26] xfs: reduce kswapd blocking on inode locking Dave Chinner 2019-10-11 10:29 ` Christoph Hellwig 2019-10-09 3:21 ` [PATCH 19/26] xfs: kill background reclaim work Dave Chinner 2019-10-11 10:31 ` Christoph Hellwig 2019-10-09 3:21 ` [PATCH 20/26] xfs: use AIL pushing for inode reclaim IO Dave Chinner 2019-10-11 17:38 ` Brian Foster 2019-10-09 3:21 ` [PATCH 21/26] xfs: remove mode from xfs_reclaim_inodes() Dave Chinner 2019-10-11 10:39 ` Christoph Hellwig 2019-10-14 13:07 ` Brian Foster 2019-10-09 3:21 ` [PATCH 22/26] xfs: track reclaimable inodes using a LRU list Dave Chinner 2019-10-11 10:42 ` Christoph Hellwig 2019-10-14 13:07 ` Brian Foster 2019-10-09 3:21 ` [PATCH 23/26] xfs: reclaim inodes from the LRU Dave Chinner 2019-10-11 10:56 ` Christoph Hellwig 2019-10-30 23:25 ` Dave Chinner 2019-10-09 3:21 ` [PATCH 24/26] xfs: remove unusued old inode reclaim code Dave Chinner 2019-10-09 3:21 ` [PATCH 25/26] xfs: rework unreferenced inode lookups Dave Chinner 2019-10-11 12:55 ` Christoph Hellwig 2019-10-11 13:39 ` Peter Zijlstra 2019-10-11 23:38 ` Dave Chinner 2019-10-14 13:07 ` Brian Foster 2019-10-17 1:24 ` Dave Chinner 2019-10-17 7:57 ` Brian Foster 2019-10-18 20:29 ` Dave Chinner 2019-10-09 3:21 ` [PATCH 26/26] xfs: use xfs_ail_push_all_sync in xfs_reclaim_inodes Dave Chinner 2019-10-11 9:55 ` Christoph Hellwig 2019-10-09 7:06 ` [PATCH V2 00/26] mm, xfs: non-blocking inode reclaim Christoph Hellwig 2019-10-11 19:03 ` Josef Bacik 2019-10-11 23:48 ` Dave Chinner 2019-10-12 0:19 ` Josef Bacik 2019-10-12 0:48 ` Dave Chinner
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