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From: Matthew Wilcox <willy@infradead.org>
To: Chris Mason <clm@fb.com>
Cc: Dave Chinner <david@fromorbit.com>,
	"linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
	Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH 09/24] xfs: don't allow log IO to be throttled
Date: Fri, 2 Aug 2019 11:34:19 -0700	[thread overview]
Message-ID: <20190802183419.GC5597@bombadil.infradead.org> (raw)
In-Reply-To: <7093F5C3-53D2-4C49-9C0D-64B20C565D18@fb.com>

On Fri, Aug 02, 2019 at 02:11:53PM +0000, Chris Mason wrote:
> Yes and no.  At some point important FS threads have the potential to 
> wait on every single REQ_META IO on the box, so every single REQ_META IO 
> has the potential to create priority inversions.

[...]

> Tejun reminded me that in a lot of ways, swap is user IO and it's 
> actually fine to have it prioritized at the same level as user IO.  We 
> don't want to let a low prio app thrash the drive swapping things in and 
> out all the time, and it's actually fine to make them wait as long as 
> other higher priority processes aren't waiting for the memory.  This 
> depends on the cgroup config, so wrt your current patches it probably 
> sounds crazy, but we have a lot of data around this from the fleet.

swap is only user IO if we're doing the swapping in response to an
allocation done on behalf of a user thread.  If one of the above-mentioned
important FS threads does a memory allocation which causes swapping,
that priority needs to be inherited by the IO.

  reply	other threads:[~2019-08-02 18:34 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 [this message]
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
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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