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Re: page fault scalability (ext3, ext4, xfs)

To: Theodore Ts'o <tytso@xxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, Jan Kara <jack@xxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, david@xxxxxxxxxxxxx, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>, Andi Kleen <ak@xxxxxxxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Subject: Re: page fault scalability (ext3, ext4, xfs)
From: Dave Hansen <dave.hansen@xxxxxxxxx>
Date: Wed, 14 Aug 2013 13:50:02 -0700
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20130814194359.GA22316@xxxxxxxxx>
References: <520BB9EF.5020308@xxxxxxxxxxxxxxx> <20130814194359.GA22316@xxxxxxxxx>
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8
On 08/14/2013 12:43 PM, Theodore Ts'o wrote:
> Thanks dave for doing this comparison.  Is there any chance you can
> check whether lockstats shows anything interesting?
> 
>> Test case is this:
>>
>>      
>> https://github.com/antonblanchard/will-it-scale/blob/master/tests/page_fault3.c
> 
> One interesting thing about the test case.  It looks like the first
> time through the while loop, the file will need to be extended (since
> it is a new tempfile).  But subsequent times through the list the
> blocks for the file will already be allocated.  If the file is
> prezero'ed ahead of time, so we're only measuring the cost of the
> write page fault, and we take block allocation out of the comparison,
> do we see the same scalability curve?

Would a plain old fallocate() do the trick, or does it actually need
zeros written to it?

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