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 [thread overview]
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 other threads:[~2019-10-11 12:40 UTC|newest]
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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