From: Dave Chinner <david@fromorbit.com>
To: Brian Foster <bfoster@redhat.com>
Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 24/28] xfs: reclaim inodes from the LRU
Date: Fri, 15 Nov 2019 08:51:56 +1100 [thread overview]
Message-ID: <20191114215156.GH4614@dread.disaster.area> (raw)
In-Reply-To: <20191106172104.GB37080@bfoster>
On Wed, Nov 06, 2019 at 12:21:04PM -0500, Brian Foster wrote:
> On Fri, Nov 01, 2019 at 10:46:14AM +1100, Dave Chinner wrote:
> > - struct xfs_inode *ip,
> > - int flags,
> > - xfs_lsn_t *lsn)
> > +enum lru_status
> > +xfs_inode_reclaim_isolate(
> > + struct list_head *item,
> > + struct list_lru_one *lru,
> > + spinlock_t *lru_lock,
>
> Did we ever establish whether we should cycle the lru_lock during long
> running scans?
I'm still evaluating this.
In theory, because it's non-blocking, the lock hold time isn't huge,
but OTOH I think the hold time is causing lock contention problems on
unlink workloads. I've found a bunch of perf/blocking problems in
the last few days, and each one of them I sort out puts more
pressure on the lru list lock on unlinks.
> > - /*
> > - * Do unlocked checks to see if the inode already is being flushed or in
> > - * reclaim to avoid lock traffic. If the inode is not clean, return the
> > - * position in the AIL for the caller to push to.
> > - */
> > - if (!xfs_inode_clean(ip)) {
> > - *lsn = ip->i_itemp->ili_item.li_lsn;
> > - return false;
> > + if (!__xfs_iflock_nowait(ip)) {
> > + lsn = ip->i_itemp->ili_item.li_lsn;
>
> This looks like a potential crash vector if we ever got here with a
> clean inode.
I'm not sure we can ever fail a flush lock attempt on a clean inode.
But I'll rework the lsn grabbing, I think.
> > + ra->dirty_skipped++;
> > + goto out_unlock_inode;
> > }
> >
> > - if (__xfs_iflags_test(ip, XFS_IFLOCK | XFS_IRECLAIM))
> > - return false;
> > + if (XFS_FORCED_SHUTDOWN(ip->i_mount))
> > + goto reclaim;
> >
> > /*
> > - * The radix tree lock here protects a thread in xfs_iget from racing
> > - * with us starting reclaim on the inode. Once we have the
> > - * XFS_IRECLAIM flag set it will not touch us.
> > - *
> > - * Due to RCU lookup, we may find inodes that have been freed and only
> > - * have XFS_IRECLAIM set. Indeed, we may see reallocated inodes that
> > - * aren't candidates for reclaim at all, so we must check the
> > - * XFS_IRECLAIMABLE is set first before proceeding to reclaim.
> > + * Now the inode is locked, we can actually determine if it is dirty
> > + * without racing with anything.
> > */
> > - spin_lock(&ip->i_flags_lock);
> > - if (!__xfs_iflags_test(ip, XFS_IRECLAIMABLE) ||
> > - __xfs_iflags_test(ip, XFS_IRECLAIM)) {
> > - /* not a reclaim candidate. */
> > - spin_unlock(&ip->i_flags_lock);
> > - return false;
> > + ret = LRU_ROTATE;
> > + if (xfs_ipincount(ip)) {
> > + ra->dirty_skipped++;
>
> Hmm.. didn't we have an LSN check here?
Yes, but if the inode was not in the AIL, it would crash, so I
removed it :P
> Altogether, I think the logic in this function would be a lot more
> simple if we had something like the following:
>
> ...
> /* ret == LRU_SKIP */
> if (!xfs_inode_clean(ip)) {
> ret = LRU_ROTATE;
> lsn = ip->i_itemp->ili_item.li_lsn;
> ra->dirty_skipped++;
> }
> if (lsn && XFS_LSN_CMP(lsn, ra->lowest_lsn) < 0)
> ra->lowest_lsn = lsn;
> return ret;
>
> ... as the non-reclaim exit path.
Yeah, that was what I was thinking when you pointed out the
iflock_nowait issue above. I'll end up with something like this, I
think....
> > void
> > xfs_reclaim_all_inodes(
> > struct xfs_mount *mp)
> > {
> ...
> > + while (list_lru_count(&mp->m_inode_lru)) {
>
> It seems unnecessary to call this twice per-iter:
>
> while ((to_free = list_lru_count(&mp->m_inode_lru))) {
> ...
> }
*nod*.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2019-11-14 21:52 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
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 [this message]
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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