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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 17/24] xfs: don't block kswapd in inode reclaim
Date: Tue, 6 Aug 2019 14:21:31 -0400	[thread overview]
Message-ID: <20190806182131.GE2979@bfoster> (raw)
In-Reply-To: <20190801021752.4986-18-david@fromorbit.com>

On Thu, Aug 01, 2019 at 12:17:45PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> We have a number of reasons for blocking kswapd in XFS inode
> reclaim, mainly all to do with the fact that memory reclaim has no
> feedback mechanisms to throttle on dirty slab objects that need IO
> to reclaim.
> 
> As a result, we currently throttle inode reclaim by issuing IO in
> the reclaim context. The unfortunate side effect of this is that it
> can cause long tail latencies in reclaim and for some workloads this
> can be a problem.
> 
> Now that the shrinkers finally have a method of telling kswapd to
> back off, we can start the process of making inode reclaim in XFS
> non-blocking. The first thing we need to do is not block kswapd, but
> so that doesn't cause immediate serious problems, make sure inode
> writeback is always underway when kswapd is running.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/xfs_icache.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
> index 0b0fd10a36d4..2fa2f8dcf86b 100644
> --- a/fs/xfs/xfs_icache.c
> +++ b/fs/xfs/xfs_icache.c
> @@ -1378,11 +1378,22 @@ xfs_reclaim_inodes_nr(
>  	struct xfs_mount	*mp,
>  	int			nr_to_scan)
>  {
> -	/* kick background reclaimer and push the AIL */
> +	int			sync_mode = SYNC_TRYLOCK;
> +
> +	/* kick background reclaimer */
>  	xfs_reclaim_work_queue(mp);
> -	xfs_ail_push_all(mp->m_ail);
>  
> -	return xfs_reclaim_inodes_ag(mp, SYNC_TRYLOCK | SYNC_WAIT, &nr_to_scan);
> +	/*
> +	 * For kswapd, we kick background inode writeback. For direct
> +	 * reclaim, we issue and wait on inode writeback to throttle
> +	 * reclaim rates and avoid shouty OOM-death.
> +	 */
> +	if (current_is_kswapd())
> +		xfs_ail_push_all(mp->m_ail);

So we're unblocking kswapd from dirty items, but we already kick the AIL
regardless of kswapd or not in inode reclaim. Why the change to no
longer kick the AIL in the !kswapd case? Whatever the reasoning, a
mention in the commit log would be helpful...

Brian

> +	else
> +		sync_mode |= SYNC_WAIT;
> +
> +	return xfs_reclaim_inodes_ag(mp, sync_mode, &nr_to_scan);
>  }
>  
>  /*
> -- 
> 2.22.0
> 

  reply	other threads:[~2019-08-06 18:21 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-01  2:17 [RFC] [PATCH 00/24] mm, xfs: non-blocking inode reclaim Dave Chinner
2019-08-01  2:17 ` [PATCH 01/24] mm: directed shrinker work deferral Dave Chinner
2019-08-02 15:27   ` Brian Foster
2019-08-04  1:49     ` Dave Chinner
2019-08-05 17:42       ` Brian Foster
2019-08-05 23:43         ` Dave Chinner
2019-08-06 12:27           ` Brian Foster
2019-08-06 22:22             ` Dave Chinner
2019-08-07 11:13               ` Brian Foster
2019-08-01  2:17 ` [PATCH 02/24] shrinkers: use will_defer for GFP_NOFS sensitive shrinkers Dave Chinner
2019-08-02 15:27   ` Brian Foster
2019-08-04  1:50     ` Dave Chinner
2019-08-01  2:17 ` [PATCH 03/24] mm: factor shrinker work calculations Dave Chinner
2019-08-02 15:08   ` Nikolay Borisov
2019-08-04  2:05     ` Dave Chinner
2019-08-02 15:31   ` Brian Foster
2019-08-01  2:17 ` [PATCH 04/24] shrinker: defer work only to kswapd Dave Chinner
2019-08-02 15:34   ` Brian Foster
2019-08-04 16:48   ` Nikolay Borisov
2019-08-04 21:37     ` Dave Chinner
2019-08-07 16:12   ` kbuild test robot
2019-08-07 18:00   ` kbuild test robot
2019-08-01  2:17 ` [PATCH 05/24] shrinker: clean up variable types and tracepoints Dave Chinner
2019-08-01  2:17 ` [PATCH 06/24] mm: reclaim_state records pages reclaimed, not slabs Dave Chinner
2019-08-01  2:17 ` [PATCH 07/24] mm: back off direct reclaim on excessive shrinker deferral Dave Chinner
2019-08-01  2:17 ` [PATCH 08/24] mm: kswapd backoff for shrinkers Dave Chinner
2019-08-01  2:17 ` [PATCH 09/24] xfs: don't allow log IO to be throttled Dave Chinner
2019-08-01 13:39   ` Chris Mason
2019-08-01 23:58     ` Dave Chinner
2019-08-02  8:12       ` Christoph Hellwig
2019-08-02 14:11       ` Chris Mason
2019-08-02 18:34         ` Matthew Wilcox
2019-08-02 23:28         ` Dave Chinner
2019-08-05 18:32           ` Chris Mason
2019-08-05 23:09             ` Dave Chinner
2019-08-01  2:17 ` [PATCH 10/24] xfs: fix missed wakeup on l_flush_wait Dave Chinner
2019-08-01  2:17 ` [PATCH 11/24] xfs:: account for memory freed from metadata buffers Dave Chinner
2019-08-01  8:16   ` Christoph Hellwig
2019-08-01  9:21     ` Dave Chinner
2019-08-06  5:51       ` Christoph Hellwig
2019-08-01  2:17 ` [PATCH 12/24] xfs: correctly acount for reclaimable slabs Dave Chinner
2019-08-06  5:52   ` Christoph Hellwig
2019-08-06 21:05     ` Dave Chinner
2019-08-01  2:17 ` [PATCH 13/24] xfs: synchronous AIL pushing Dave Chinner
2019-08-05 17:51   ` Brian Foster
2019-08-05 23:21     ` Dave Chinner
2019-08-06 12:29       ` Brian Foster
2019-08-01  2:17 ` [PATCH 14/24] xfs: tail updates only need to occur when LSN changes Dave Chinner
2019-08-05 17:53   ` Brian Foster
2019-08-05 23:28     ` Dave Chinner
2019-08-06  5:33       ` Dave Chinner
2019-08-06 12:53         ` Brian Foster
2019-08-06 21:11           ` Dave Chinner
2019-08-01  2:17 ` [PATCH 15/24] xfs: eagerly free shadow buffers to reduce CIL footprint Dave Chinner
2019-08-05 18:03   ` Brian Foster
2019-08-05 23:33     ` Dave Chinner
2019-08-06 12:57       ` Brian Foster
2019-08-06 21:21         ` Dave Chinner
2019-08-01  2:17 ` [PATCH 16/24] xfs: Lower CIL flush limit for large logs Dave Chinner
2019-08-04 17:12   ` Nikolay Borisov
2019-08-01  2:17 ` [PATCH 17/24] xfs: don't block kswapd in inode reclaim Dave Chinner
2019-08-06 18:21   ` Brian Foster [this message]
2019-08-06 21:27     ` Dave Chinner
2019-08-07 11:14       ` Brian Foster
2019-08-01  2:17 ` [PATCH 18/24] xfs: reduce kswapd blocking on inode locking Dave Chinner
2019-08-06 18:22   ` Brian Foster
2019-08-06 21:33     ` Dave Chinner
2019-08-07 11:30       ` Brian Foster
2019-08-07 23:16         ` Dave Chinner
2019-08-01  2:17 ` [PATCH 19/24] xfs: kill background reclaim work Dave Chinner
2019-08-01  2:17 ` [PATCH 20/24] xfs: use AIL pushing for inode reclaim IO Dave Chinner
2019-08-07 18:09   ` Brian Foster
2019-08-07 23:10     ` Dave Chinner
2019-08-08 16:20       ` Brian Foster
2019-08-01  2:17 ` [PATCH 21/24] xfs: remove mode from xfs_reclaim_inodes() Dave Chinner
2019-08-01  2:17 ` [PATCH 22/24] xfs: track reclaimable inodes using a LRU list Dave Chinner
2019-08-08 16:36   ` Brian Foster
2019-08-09  0:10     ` Dave Chinner
2019-08-01  2:17 ` [PATCH 23/24] xfs: reclaim inodes from the LRU Dave Chinner
2019-08-08 16:39   ` Brian Foster
2019-08-09  1:20     ` Dave Chinner
2019-08-09 12:36       ` Brian Foster
2019-08-11  2:17         ` Dave Chinner
2019-08-11 12:46           ` Brian Foster
2019-08-01  2:17 ` [PATCH 24/24] xfs: remove unusued old inode reclaim code Dave Chinner
2019-08-06  5:57 ` [RFC] [PATCH 00/24] mm, xfs: non-blocking inode reclaim Christoph Hellwig
2019-08-06 21:37   ` Dave Chinner

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