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Re: Valid Benchmark Value & Methods

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: Valid Benchmark Value & Methods
From: Dewangga Bachrul Alam <dewanggaba@xxxxxxxxxxxxxxx>
Date: Fri, 08 May 2015 12:53:46 +0700
Cc: Martin Steigerwald <martin@xxxxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
Disposition-notification-to: Dewangga Bachrul Alam <dewanggaba@xxxxxxxxxxxxxxx>
In-reply-to: <20150507225521.GB16689@dastard>
References: <554B4B59.6000706@xxxxxxxxxxxxxxx> <2204700.QypQcg3ER3@merkaba> <554B5782.4040303@xxxxxxxxxxxxxxx> <20150507225521.GB16689@dastard>
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Hello Dave!

On 05/08/2015 05:55 AM, Dave Chinner wrote:
> On Thu, May 07, 2015 at 07:16:02PM +0700, Dewangga wrote:
>> Hash: SHA1
>> Hello Martin,
>> Thanks for your reply, yes I've read that link, but another question,
>> is noatime,nodiratime,etc still valid for performance tuning guidance?
> You may have read it, but I don't think it sunk in....
>> Even the default mount options only "rw,inode64,seclabel,attr2".
> Where's relatime(*)? That's been a default for a lot longer than
> inode64...
> $ grep "root " /proc/mounts
> /dev/root / xfs rw,relatime,attr2,inode64,noquota 0 0
> $

I forgot write it, but relatime still exists on default mount options.

>> Is it still increase the performance if the additional mount options
>> added?
> Depends on your workload, which is more critical to understand than
> anything else. Why? because it's your workload that is going to
> determine if twiddling a knob is going to have any effect on
> performance. Once you understand the workload and what the
> bottlenecks are, then you can look at what knobs the filesystem
> provides to alleviate those bottlenecks.
> IOWs, asking the question "how do I tune my filesystem for best
> performance" is, fundamentally, the wrong way to go about obtaining
> best filesystem performance.  The questions that need to be answered
> are "what bottlenecks does my application have?" followed by "what
> does the filesystem provide to alleviate those bottlenecks".
> i.e. understand the problem you need to solve *before* you try to
> solve it, otherwise you "solve" the wrong problem...
> Cheers,
> Dave.
> (*) An example of exactly what I'm talking abou there. The default
> option of relatime gets >95% of the benefit of noatime onmost
> workloads compared to the old strictatime behaviour, but unlike
> noatime it still retains atime updates. IOWs there's a pretty good
> chance that noatime has little measurable impact on your
> application's performance, but understanding and benchmarking
> anything other than your application won't tell you this.

Okay dave, got it. Standard optimize performance is add mount options
like noatime and nodiratime, any additional performance tune is depends
on the apps and the workloads.

Thanks anyway :)

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