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Re: xfs: very slow after mount, very slow at umount

To: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Subject: Re: xfs: very slow after mount, very slow at umount
From: Mark Lord <kernel@xxxxxxxxxxxx>
Date: Thu, 27 Jan 2011 11:03:49 -0500
Cc: Stan Hoeppner <stan@xxxxxxxxxxxxxxxxx>, Christoph Hellwig <hch@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, Linux Kernel <linux-kernel@xxxxxxxxxxxxxxx>, Alex Elder <aelder@xxxxxxx>
In-reply-to: <alpine.DEB.2.00.1101271040000.31246@xxxxxxxxxxxxxxxx>
References: <4D40C8D1.8090202@xxxxxxxxxxxx> <20110127033011.GH21311@dastard> <4D40EB2F.2050809@xxxxxxxxxxxx> <4D418B57.1000501@xxxxxxxxxxxx> <alpine.DEB.2.00.1101271040000.31246@xxxxxxxxxxxxxxxx>
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On 11-01-27 10:40 AM, Justin Piszcz wrote:
> On Thu, 27 Jan 2011, Mark Lord wrote:
>> Can you recommend a good set of mkfs.xfs parameters to suit the 
>> characteristics
>> of this system?  Eg. Only a few thousand active inodes, and nearly all files 
>> are
>> in the 600MB -> 20GB size range.  The usage pattern it must handle is up to
>> six concurrent streaming writes at the same time as up to three streaming 
>> reads,
>> with no significant delays permitted on the reads.
>> That's the kind of workload that I find XFS handles nicely,
>> and EXT4 has given me trouble with in the past.
> I did a load of benchmarks a long time ago testing every mkfs.xfs option there
> was, and I found that most of the time (if not all), the defaults were the 
> best.

I am concerned with fragmentation on the very special workload in this case.
I'd really like the 20GB files, written over a 1-2 hour period, to consist
of a very few very large extents, as much as possible.

Rather than hundreds or thousands of "tiny" MB sized extents.
I wonder what the best mkfs.xfs parameters might be to encourage that?


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