From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 07/28] xfs: tail updates only need to occur when LSN changes
Date: Mon, 4 Nov 2019 15:18:34 -0800 [thread overview]
Message-ID: <20191104231834.GQ4153244@magnolia> (raw)
In-Reply-To: <20191031234618.15403-8-david@fromorbit.com>
On Fri, Nov 01, 2019 at 10:45:57AM +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>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Brian Foster <bfoster@redhat.com>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
--D
> ---
> 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_inode_item.c b/fs/xfs/xfs_inode_item.c
> index ab12e526540a..79ffe6dff115 100644
> --- a/fs/xfs/xfs_inode_item.c
> +++ b/fs/xfs/xfs_inode_item.c
> @@ -731,19 +731,27 @@ xfs_iflush_done(
> * holding the lock before removing the inode from the AIL.
> */
> if (need_ail) {
> - bool mlip_changed = false;
> + xfs_lsn_t tail_lsn = 0;
>
> /* this is an opencoded batch version of xfs_trans_ail_delete */
> spin_lock(&ailp->ail_lock);
> list_for_each_entry(blip, &tmp, li_bio_list) {
> if (INODE_ITEM(blip)->ili_logged &&
> - blip->li_lsn == INODE_ITEM(blip)->ili_flush_lsn)
> - mlip_changed |= xfs_ail_delete_one(ailp, blip);
> - else {
> + blip->li_lsn == INODE_ITEM(blip)->ili_flush_lsn) {
> + /*
> + * xfs_ail_update_finish() only cares about the
> + * lsn of the first tail item removed, any
> + * others will be at the same or higher lsn so
> + * we just ignore them.
> + */
> + xfs_lsn_t lsn = xfs_ail_delete_one(ailp, blip);
> + if (!tail_lsn && lsn)
> + tail_lsn = lsn;
> + } else {
> xfs_clear_li_failed(blip);
> }
> }
> - xfs_ail_update_finish(ailp, mlip_changed);
> + xfs_ail_update_finish(ailp, tail_lsn);
> }
>
> /*
> 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
> @@ -108,17 +108,25 @@ xfs_ail_next(
> * We need the AIL lock in order to get a coherent read of the lsn of the last
> * item in the AIL.
> */
> +static xfs_lsn_t
> +__xfs_ail_min_lsn(
> + struct xfs_ail *ailp)
> +{
> + struct xfs_log_item *lip = xfs_ail_min(ailp);
> +
> + if (lip)
> + return lip->li_lsn;
> + return 0;
> +}
> +
> xfs_lsn_t
> xfs_ail_min_lsn(
> struct xfs_ail *ailp)
> {
> - xfs_lsn_t lsn = 0;
> - struct xfs_log_item *lip;
> + xfs_lsn_t lsn;
>
> spin_lock(&ailp->ail_lock);
> - lip = xfs_ail_min(ailp);
> - if (lip)
> - lsn = lip->li_lsn;
> + lsn = __xfs_ail_min_lsn(ailp);
> spin_unlock(&ailp->ail_lock);
>
> return lsn;
> @@ -681,11 +689,12 @@ xfs_ail_push_all_sync(
> void
> xfs_ail_update_finish(
> struct xfs_ail *ailp,
> - bool do_tail_update) __releases(ailp->ail_lock)
> + xfs_lsn_t old_lsn) __releases(ailp->ail_lock)
> {
> struct xfs_mount *mp = ailp->ail_mount;
>
> - if (!do_tail_update) {
> + /* if the tail lsn hasn't changed, don't do updates or wakeups. */
> + if (!old_lsn || old_lsn == __xfs_ail_min_lsn(ailp)) {
> spin_unlock(&ailp->ail_lock);
> return;
> }
> @@ -730,7 +739,7 @@ xfs_trans_ail_update_bulk(
> xfs_lsn_t lsn) __releases(ailp->ail_lock)
> {
> struct xfs_log_item *mlip;
> - int mlip_changed = 0;
> + xfs_lsn_t tail_lsn = 0;
> int i;
> LIST_HEAD(tmp);
>
> @@ -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;
> } 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);
> --
> 2.24.0.rc0
>
next prev parent reply other threads:[~2019-11-04 23:18 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-31 23:45 [PATCH 00/28] mm, xfs: non-blocking inode reclaim Dave Chinner
2019-10-31 23:45 ` [PATCH 01/28] xfs: Lower CIL flush limit for large logs Dave Chinner
2019-10-31 23:45 ` [PATCH 02/28] xfs: Throttle commits on delayed background CIL push Dave Chinner
2019-11-01 12:04 ` Brian Foster
2019-11-01 21:40 ` Dave Chinner
2019-11-04 22:48 ` Darrick J. Wong
2019-10-31 23:45 ` [PATCH 03/28] xfs: don't allow log IO to be throttled Dave Chinner
2019-10-31 23:45 ` [PATCH 04/28] xfs: Improve metadata buffer reclaim accountability Dave Chinner
2019-11-01 12:05 ` Brian Foster
2019-11-04 23:21 ` Darrick J. Wong
2019-10-31 23:45 ` [PATCH 05/28] xfs: correctly acount for reclaimable slabs Dave Chinner
2019-10-31 23:45 ` [PATCH 06/28] xfs: factor common AIL item deletion code Dave Chinner
2019-11-04 23:16 ` Darrick J. Wong
2019-10-31 23:45 ` [PATCH 07/28] xfs: tail updates only need to occur when LSN changes Dave Chinner
2019-11-04 23:18 ` Darrick J. Wong [this message]
2019-10-31 23:45 ` [PATCH 08/28] xfs: factor inode lookup from xfs_ifree_cluster Dave Chinner
2019-11-01 12:05 ` Brian Foster
2019-11-04 23:20 ` Darrick J. Wong
2019-10-31 23:45 ` [PATCH 09/28] mm: directed shrinker work deferral Dave Chinner
2019-11-04 15:25 ` Brian Foster
2019-11-14 20:49 ` Dave Chinner
2019-11-15 17:21 ` Brian Foster
2019-11-18 0:49 ` Dave Chinner
2019-11-19 15:12 ` Brian Foster
2019-10-31 23:46 ` [PATCH 10/28] shrinkers: use defer_work for GFP_NOFS sensitive shrinkers Dave Chinner
2019-10-31 23:46 ` [PATCH 11/28] mm: factor shrinker work calculations Dave Chinner
2019-11-02 10:55 ` kbuild test robot
2019-11-04 15:29 ` Brian Foster
2019-11-14 20:59 ` Dave Chinner
2019-10-31 23:46 ` [PATCH 12/28] shrinker: defer work only to kswapd Dave Chinner
2019-11-04 15:29 ` Brian Foster
2019-11-14 21:11 ` Dave Chinner
2019-11-15 17:23 ` Brian Foster
2019-10-31 23:46 ` [PATCH 13/28] shrinker: clean up variable types and tracepoints Dave Chinner
2019-11-04 15:30 ` Brian Foster
2019-10-31 23:46 ` [PATCH 14/28] mm: reclaim_state records pages reclaimed, not slabs Dave Chinner
2019-11-04 19:58 ` Brian Foster
2019-10-31 23:46 ` [PATCH 15/28] mm: back off direct reclaim on excessive shrinker deferral Dave Chinner
2019-11-04 19:58 ` Brian Foster
2019-11-14 21:28 ` Dave Chinner
2019-10-31 23:46 ` [PATCH 16/28] mm: kswapd backoff for shrinkers Dave Chinner
2019-11-04 19:58 ` Brian Foster
2019-11-14 21:41 ` Dave Chinner
2019-10-31 23:46 ` [PATCH 17/28] xfs: synchronous AIL pushing Dave Chinner
2019-11-05 17:05 ` Brian Foster
2019-10-31 23:46 ` [PATCH 18/28] xfs: don't block kswapd in inode reclaim Dave Chinner
2019-10-31 23:46 ` [PATCH 19/28] xfs: reduce kswapd blocking on inode locking Dave Chinner
2019-11-05 17:05 ` Brian Foster
2019-10-31 23:46 ` [PATCH 20/28] xfs: kill background reclaim work Dave Chinner
2019-11-05 17:05 ` Brian Foster
2019-10-31 23:46 ` [PATCH 21/28] xfs: use AIL pushing for inode reclaim IO Dave Chinner
2019-11-05 17:06 ` Brian Foster
2019-10-31 23:46 ` [PATCH 22/28] xfs: remove mode from xfs_reclaim_inodes() Dave Chinner
2019-10-31 23:46 ` [PATCH 23/28] xfs: track reclaimable inodes using a LRU list Dave Chinner
2019-10-31 23:46 ` [PATCH 24/28] xfs: reclaim inodes from the LRU Dave Chinner
2019-11-06 17:21 ` Brian Foster
2019-11-14 21:51 ` Dave Chinner
2019-10-31 23:46 ` [PATCH 25/28] xfs: remove unusued old inode reclaim code Dave Chinner
2019-11-06 17:21 ` Brian Foster
2019-10-31 23:46 ` [PATCH 26/28] xfs: use xfs_ail_push_all in xfs_reclaim_inodes Dave Chinner
2019-11-06 17:22 ` Brian Foster
2019-11-14 21:53 ` Dave Chinner
2019-10-31 23:46 ` [PATCH 27/28] rwsem: introduce down/up_write_non_owner Dave Chinner
2019-10-31 23:46 ` [PATCH 28/28] xfs: rework unreferenced inode lookups Dave Chinner
2019-11-06 22:18 ` Brian Foster
2019-11-14 22:16 ` Dave Chinner
2019-11-15 13:13 ` Christoph Hellwig
2019-11-15 17:26 ` Brian Foster
2019-11-18 1:00 ` Dave Chinner
2019-11-19 15:13 ` Brian Foster
2019-11-19 21:18 ` Dave Chinner
2019-11-20 12:42 ` Brian Foster
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