From: Ben Myers <bpm@sgi.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: xfs@oss.sgi.com
Subject: Re: [patch 02/12] xfs: do exact log space wakeups in xlog_ungrant_log_space
Date: Thu, 16 Feb 2012 12:36:59 -0600 [thread overview]
Message-ID: <20120216183659.GR7762@sgi.com> (raw)
In-Reply-To: <20111212141433.714245384@bombadil.infradead.org>
On Mon, Dec 12, 2011 at 09:13:49AM -0500, Christoph Hellwig wrote:
> The only reason that xfs_log_space_wake had to do opportunistic wakeups
> was that the old xfs_log_move_tail calling convention didn't allow for
> exact wakeups when not updating the log tail LSN.
Man, that's a doosey.
when you called xfs_log_move_tail...
if you passed tail_lsn = 1
it would: not move the tail
ignore strict accounting and wake only 1
if you passed tail_lsn = 0
it would: get tail_lsn from l_last_sync_lsn
move the tail
pay attention to strict accounting
wake as many as is correct
if you passed tail_lsn = !1, !0
it would: move the tail
pay attention to strict accounting
wake as many as is correct.
The important thing to understand is that the opportunistic wakeups
would ignore the the test (free_bytes < need_bytes) in
xfs_log_move_tail, so you could wake a process regardless of whether
there is sufficient space in the log for it. No wonder they had to
pepper the code with opportunistic wakeups to prevent log space hangs...
> Since this issue has
> been fixed we can do exact wakeups now.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
>
> ---
> fs/xfs/xfs_log.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: xfs/fs/xfs/xfs_log.c
> ===================================================================
> --- xfs.orig/fs/xfs/xfs_log.c 2011-12-11 15:30:49.977750776 +0100
> +++ xfs/fs/xfs/xfs_log.c 2011-12-11 17:49:00.692836117 +0100
> @@ -2748,7 +2748,7 @@ xlog_ungrant_log_space(xlog_t *log,
>
> trace_xfs_log_ungrant_exit(log, ticket);
>
> - xfs_log_space_wake(log->l_mp, true);
> + xfs_log_space_wake(log->l_mp, false);
Yeah, he's doing an _exact_ wakeup now.
Reviewed-by: Ben Myers <bpm@sgi.com>
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next prev parent reply other threads:[~2012-02-16 18:36 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-12 14:13 [patch 00/12] log grant code cleanups Christoph Hellwig
2011-12-12 14:13 ` [patch 01/12] xfs: split tail_lsn assignments from log space wakeups Christoph Hellwig
2012-01-17 18:48 ` Mark Tinguely
2012-01-25 16:09 ` Christoph Hellwig
2012-02-16 18:21 ` Ben Myers
2012-02-17 19:21 ` Christoph Hellwig
2011-12-12 14:13 ` [patch 02/12] xfs: do exact log space wakeups in xlog_ungrant_log_space Christoph Hellwig
2012-01-17 22:42 ` Mark Tinguely
2012-02-16 18:36 ` Ben Myers [this message]
2011-12-12 14:13 ` [patch 03/12] xfs: remove xfs_trans_unlocked_item Christoph Hellwig
2012-01-23 14:31 ` Mark Tinguely
2012-02-16 18:51 ` Ben Myers
2011-12-12 14:13 ` [patch 04/12] xfs: cleanup xfs_log_space_wake Christoph Hellwig
2012-01-23 19:22 ` Mark Tinguely
2012-01-25 16:10 ` Christoph Hellwig
2012-01-25 19:09 ` Mark Tinguely
2012-01-26 16:13 ` Mark Tinguely
2012-01-26 22:12 ` Dave Chinner
2012-02-16 19:06 ` Ben Myers
2011-12-12 14:13 ` [patch 05/12] xfs: remove log space waitqueues Christoph Hellwig
2012-01-23 21:58 ` Mark Tinguely
2011-12-12 14:13 ` [patch 06/12] xfs: add the xlog_grant_head structure Christoph Hellwig
2012-01-24 15:35 ` Mark Tinguely
2012-02-16 20:23 ` Ben Myers
2011-12-12 14:13 ` [patch 07/12] xfs: add xlog_grant_head_init Christoph Hellwig
2012-01-24 15:43 ` Mark Tinguely
2012-02-16 20:29 ` Ben Myers
2011-12-12 14:13 ` [patch 08/12] xfs: add xlog_grant_head_wake_all Christoph Hellwig
2012-01-24 15:46 ` Mark Tinguely
2012-02-16 20:44 ` Ben Myers
2011-12-12 14:13 ` [patch 09/12] xfs: share code for grant head waiting Christoph Hellwig
2012-01-24 18:10 ` Mark Tinguely
2012-02-16 20:51 ` Ben Myers
2011-12-12 14:13 ` [patch 10/12] xfs: shared code for grant head wakeups Christoph Hellwig
2012-01-24 18:37 ` Mark Tinguely
2012-02-16 21:08 ` Ben Myers
2011-12-12 14:13 ` [patch 11/12] xfs: share code for grant head availability checks Christoph Hellwig
2012-01-24 18:53 ` Mark Tinguely
2012-02-16 21:25 ` Ben Myers
2012-02-17 2:41 ` Dave Chinner
2011-12-12 14:13 ` [patch 12/12] xfs: split and cleanup xfs_log_reserve Christoph Hellwig
2012-02-16 21:36 ` Ben Myers
2012-02-19 21:16 ` Christoph Hellwig
2012-02-16 6:16 ` [patch 00/12] log grant code cleanups Dave Chinner
2012-02-17 18:00 ` Christoph Hellwig
2012-02-16 21:46 ` Ben Myers
2012-02-19 21:17 ` Christoph Hellwig
2012-02-20 21:59 ` Ben Myers
-- strict thread matches above, loose matches on Subject: below --
2012-02-20 2:31 [PATCH 00/12] log grant code cleanups V2 Christoph Hellwig
2012-02-20 2:31 ` [PATCH 02/12] xfs: do exact log space wakeups in xlog_ungrant_log_space Christoph Hellwig
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