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

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Message-ID: <CALCETrVayD1P2a8ShjZ2e4HYGwL_yE8FM7GnrWaL9MgXYMGvHg@mail.gmail.com>
Date:	Wed, 4 Sep 2013 10:33:22 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Jan Kara <jack@...e.cz>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-ext4@...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,
	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 Wed, Sep 4, 2013 at 8:08 AM, Jan Kara <jack@...e.cz> wrote:
> 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...

Will do, although the data from my workload will be a little strange.

I was hoping that Dave Hansen would re-run his benchmark with these
patches applied.  I tried to run it, but it wasn't obvious what the
numbers that spewed out meant.

--Andy

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



-- 
Andy Lutomirski
AMA Capital Management, LLC
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