From: Dave Chinner <david@fromorbit.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 08/16] xfs: implement lazy removal for the dquot freelist
Date: Mon, 5 Dec 2011 15:32:31 +1100 [thread overview]
Message-ID: <20111205043230.GO7046@dastard> (raw)
In-Reply-To: <20111128082837.638600213@bombadil.infradead.org>
On Mon, Nov 28, 2011 at 03:27:30AM -0500, Christoph Hellwig wrote:
> Do not remove dquots from the freelist when we grab a reference to them in
> xfs_qm_dqlookup, but leave them on the freelist util scanning notices that
> they have a reference. This speeds up the lookup fastpath, and greatly
> simplifies the lock ordering constraints. Note that the same scheme is
> used by the VFS inode and dentry caches.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
That cleans things up nicely, and should be significantly faster if
the VFS cache examples are anything to go by....
Reviewed-by: Dave Chinner <dchinner@redhat.com>
As an aside:
> + /*
> + * move the dquot to the front of the hashchain
> + */
> + list_move(&dqp->q_hashlist, &qh->qh_list);
> + trace_xfs_dqlookup_done(dqp);
> + *O_dqpp = dqp;
> + return 0;
Back when the inode cache used a hash, we found that this moving of
the item to the front of the list actually slowed down lookups - the
impact of dirtying cachelines (i.e. remote CPU cache invalidation)
to move the item in the list was greater than the time saved during
lookups. That was because that when there are no hash chain
modifications taking place, then the frequently hit chains simply
end up shared in all the cpu caches rather than being turfed out on
every successful lookup on a different CPU....
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2011-12-05 4:49 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-28 8:27 [PATCH 00/16] quota cleanups for Linux 3.3 Christoph Hellwig
2011-11-28 8:27 ` [PATCH 01/16] xfs: untange SYNC_WAIT and SYNC_TRYLOCK meanings for xfs_qm_dqflush Christoph Hellwig
2011-12-05 3:57 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 02/16] xfs: make sure to really flush all dquots in xfs_qm_quotacheck Christoph Hellwig
2011-12-05 3:59 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 03/16] xfs: remove xfs_qm_sync Christoph Hellwig
2011-12-05 4:09 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 04/16] xfs: remove the sync_mode argument to xfs_qm_dqflush_all Christoph Hellwig
2011-12-05 4:09 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 05/16] xfs: cleanup dquot locking helpers Christoph Hellwig
2011-12-05 4:12 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 06/16] xfs: cleanup xfs_qm_dqlookup Christoph Hellwig
2011-12-05 4:17 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 07/16] xfs: remove XFS_DQ_INACTIVE Christoph Hellwig
2011-12-05 4:23 ` Dave Chinner
2011-12-05 8:37 ` Christoph Hellwig
2011-12-06 14:43 ` Christoph Hellwig
2011-12-06 20:34 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 08/16] xfs: implement lazy removal for the dquot freelist Christoph Hellwig
2011-12-05 4:32 ` Dave Chinner [this message]
2011-12-05 8:38 ` Christoph Hellwig
2011-11-28 8:27 ` [PATCH 09/16] xfs: flatten the dquot lock ordering Christoph Hellwig
2011-12-05 5:04 ` Dave Chinner
2011-12-05 9:11 ` Christoph Hellwig
2011-12-05 9:34 ` Dave Chinner
2011-12-05 11:50 ` Christoph Hellwig
2011-12-06 0:25 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 10/16] xfs: nest qm_dqfrlist_lock insise the dquot qlock Christoph Hellwig
2011-12-05 5:10 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 11/16] xfs: simplify xfs_qm_dqattach_grouphint Christoph Hellwig
2011-12-05 5:14 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 12/16] xfs: simplify xfs_qm_detach_gdquots Christoph Hellwig
2011-12-05 5:18 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 13/16] xfs: add a xfs_dqhold helper Christoph Hellwig
2011-12-05 5:22 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 14/16] xfs: merge xfs_qm_dqinit_core into the only caller Christoph Hellwig
2011-12-05 5:23 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 15/16] xfs: kill xfs_qm_idtodq Christoph Hellwig
2011-12-05 5:31 ` Dave Chinner
2011-11-28 8:27 ` [PATCH 16/16] xfs: remove XFS_QMOPT_DQSUSER Christoph Hellwig
2011-12-05 5:34 ` Dave Chinner
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