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

To: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Subject: Re: [PATCH v3 0/5] Rework mtime and ctime updates on mmaped writes
From: Jan Kara <jack@xxxxxxx>
Date: Wed, 4 Sep 2013 17:08:54 +0200
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, Dave Chinner <david@xxxxxxxxxxxxx>, Theodore Ts'o <tytso@xxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, Jan Kara <jack@xxxxxxx>, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <cover.1377193658.git.luto@xxxxxxxxxxxxxx>
References: <cover.1377193658.git.luto@xxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
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@xxxxxxx>
SUSE Labs, CR

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