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From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Brian Foster <bfoster@redhat.com>,
	Dave Chinner <david@fromorbit.com>,
	Ritesh Harjani <riteshh@linux.ibm.com>,
	Anju T Sudhakar <anju@linux.vnet.ibm.com>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, willy@infradead.org,
	minlei@redhat.com
Subject: Re: [PATCH] iomap: Fix the write_count in iomap_add_to_ioend().
Date: Thu, 17 Sep 2020 14:33:12 -0700	[thread overview]
Message-ID: <20200917213312.GF7954@magnolia> (raw)
In-Reply-To: <20200917144804.GA31389@infradead.org>

On Thu, Sep 17, 2020 at 03:48:04PM +0100, Christoph Hellwig wrote:
> On Thu, Sep 17, 2020 at 06:42:19AM -0400, Brian Foster wrote:
> > That wouldn't address the latency concern Dave brought up. That said, I
> > have no issue with this as a targeted solution for the softlockup issue.
> > iomap_finish_ioend[s]() is common code for both the workqueue and
> > ->bi_end_io() contexts so that would require either some kind of context
> > detection (and my understanding is in_atomic() is unreliable/frowned
> > upon) or a new "atomic" parameter through iomap_finish_ioend[s]() to
> > indicate whether it's safe to reschedule. Preference?
> 
> True, it would not help with latency.  But then again the latency
> should be controlled by the writeback code not doing giant writebacks
> to start with, shouldn't it?
> 
> Any XFS/iomap specific limit also would not help with the block layer
> merging bios.

/me hasn't totally been following this thread, but iomap will also
aggregate the ioend completions; do we need to cap that to keep
latencies down?  I was assuming that amortization was always favorable,
but maybe not?

--D

  reply	other threads:[~2020-09-18  4:00 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-19 10:28 Anju T Sudhakar
2020-08-20 23:11 ` Dave Chinner
2020-08-21  4:45   ` Ritesh Harjani
2020-08-21  6:00     ` Christoph Hellwig
2020-08-21  9:09       ` Ritesh Harjani
2020-08-21 21:53     ` Dave Chinner
2020-08-22 13:13       ` Christoph Hellwig
2020-08-24 14:28         ` Brian Foster
2020-08-24 15:04           ` Christoph Hellwig
2020-08-24 15:48             ` Brian Foster
2020-08-25  0:42               ` Dave Chinner
2020-08-25 14:49                 ` Brian Foster
2020-08-31  4:01                   ` Ming Lei
2020-08-31 14:35                     ` Brian Foster
2020-09-16  0:12                   ` Darrick J. Wong
2020-09-16  8:45                     ` Christoph Hellwig
2020-09-16 13:07                       ` Brian Foster
2020-09-17  8:04                         ` Christoph Hellwig
2020-09-17 10:42                           ` Brian Foster
2020-09-17 14:48                             ` Christoph Hellwig
2020-09-17 21:33                               ` Darrick J. Wong [this message]
2020-09-17 23:13                           ` Ming Lei
2020-08-21  6:01   ` Christoph Hellwig
2020-08-21  6:07 ` Christoph Hellwig
2020-08-21  8:53   ` Ritesh Harjani
2020-08-21 14:49   ` Jens Axboe
2020-08-21 13:31 ` Matthew Wilcox

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