linux-ext4 - Re: [PATCH v3 0/5] Rework mtime and ctime updates on mmaped writes

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Date:	Wed, 4 Sep 2013 17:08:54 +0200
From:	Jan Kara <jack@...e.cz>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
	Dave Chinner <david@...morbit.com>,
	Theodore Ts'o <tytso@....edu>,
	Dave Hansen <dave.hansen@...ux.intel.com>, xfs@....sgi.com,
	Jan Kara <jack@...e.cz>, Tim Chen <tim.c.chen@...ux.intel.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH v3 0/5] Rework mtime and ctime updates on mmaped writes

On Thu 22-08-13 17:03:16, Andy Lutomirski wrote:
> Writes via mmap currently update mtime and ctime in ->page_mkwrite.
> This hurts both throughput and latency.  In workloads that dirty a
> large number of mmapped pages, ->page_mkwrite can be hot and
> file_update_time is slow and scales poorly.  Updating timestamps can
> also sleep, which hurts latency for real-time workloads.
  It would help to make your case if you posted the latency comparison
before & after the patchset in this introductory email. We can then see
how significant is the reduction of latency...

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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