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From: Dave Chinner <david@fromorbit.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	xfs@oss.sgi.com, Andy Lutomirski <luto@amacapital.net>,
	linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	Tim Chen <tim.c.chen@linux.intel.com>
Subject: Re: page fault scalability (ext3, ext4, xfs)
Date: Thu, 15 Aug 2013 14:29:30 +1000	[thread overview]
Message-ID: <20130815042930.GO6023@dastard> (raw)
In-Reply-To: <20130815022401.GQ23412@tassilo.jf.intel.com>

On Wed, Aug 14, 2013 at 07:24:01PM -0700, Andi Kleen wrote:
> > And FWIW, it's no secret that XFS has more per-operation overhead
> > than ext4 through the write path when it comes to allocation, so
> > it's no surprise that on a workload that is highly dependent on
> > allocation overhead that ext4 is a bit faster....
> 
> This cannot explain a worse scaling curve though?

The scaling curve is pretty much identical. The difference in
performance will be the overhead of timestamp updates through
the transaction subsystems of the filesystems.

> w-i-s is all about scaling.

Sure, but scaling *what*? It's spending all it's time in the
filesystem through the .page_mkwrite path. It's not a page fault
scaling test - it's a filesystem overwrite test that uses mmap.
Indeed, I bet if you replace the mmap() with a write(fd, buf, 4096)
loop, you'd get almost identical behaviour from the filesystems.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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WARNING: multiple messages have this Message-ID (diff)
From: Dave Chinner <david@fromorbit.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
	linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com,
	linux-ext4@vger.kernel.org, Jan Kara <jack@suse.cz>,
	LKML <linux-kernel@vger.kernel.org>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Andy Lutomirski <luto@amacapital.net>
Subject: Re: page fault scalability (ext3, ext4, xfs)
Date: Thu, 15 Aug 2013 14:29:30 +1000	[thread overview]
Message-ID: <20130815042930.GO6023@dastard> (raw)
In-Reply-To: <20130815022401.GQ23412@tassilo.jf.intel.com>

On Wed, Aug 14, 2013 at 07:24:01PM -0700, Andi Kleen wrote:
> > And FWIW, it's no secret that XFS has more per-operation overhead
> > than ext4 through the write path when it comes to allocation, so
> > it's no surprise that on a workload that is highly dependent on
> > allocation overhead that ext4 is a bit faster....
> 
> This cannot explain a worse scaling curve though?

The scaling curve is pretty much identical. The difference in
performance will be the overhead of timestamp updates through
the transaction subsystems of the filesystems.

> w-i-s is all about scaling.

Sure, but scaling *what*? It's spending all it's time in the
filesystem through the .page_mkwrite path. It's not a page fault
scaling test - it's a filesystem overwrite test that uses mmap.
Indeed, I bet if you replace the mmap() with a write(fd, buf, 4096)
loop, you'd get almost identical behaviour from the filesystems.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply	other threads:[~2013-08-15  4:29 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-08-14 17:10 page fault scalability (ext3, ext4, xfs) Dave Hansen
2013-08-14 17:10 ` Dave Hansen
2013-08-14 19:43 ` Theodore Ts'o
2013-08-14 19:43   ` Theodore Ts'o
2013-08-14 20:50   ` Dave Hansen
2013-08-14 20:50     ` Dave Hansen
2013-08-14 23:06     ` Theodore Ts'o
2013-08-14 23:06       ` Theodore Ts'o
2013-08-14 23:38       ` Andy Lutomirski
2013-08-15  1:11         ` Theodore Ts'o
2013-08-15  2:10           ` Dave Chinner
2013-08-15  4:32             ` Andy Lutomirski
2013-08-15  4:32               ` Andy Lutomirski
2013-08-15  6:01               ` Dave Chinner
2013-08-15  6:14                 ` Andy Lutomirski
2013-08-15  6:14                   ` Andy Lutomirski
2013-08-15  6:18                   ` David Lang
2013-08-15  6:18                     ` David Lang
2013-08-15  6:28                     ` Andy Lutomirski
2013-08-15  6:28                       ` Andy Lutomirski
2013-08-15  7:11                   ` Dave Chinner
2013-08-15  7:11                     ` Dave Chinner
2013-08-15  7:45                     ` Jan Kara
2013-08-15 21:28                       ` Dave Chinner
2013-08-15 21:28                         ` Dave Chinner
2013-08-15 21:31                         ` Andy Lutomirski
2013-08-15 21:39                           ` Dave Chinner
2013-08-19 23:23                         ` David Lang
2013-08-19 23:23                           ` David Lang
2013-08-19 23:31                           ` Andy Lutomirski
2013-08-15 15:17                     ` Andy Lutomirski
2013-08-15 15:17                       ` Andy Lutomirski
2013-08-15 21:37                       ` Dave Chinner
2013-08-15 21:37                         ` Dave Chinner
2013-08-15 21:43                         ` Andy Lutomirski
2013-08-15 21:43                           ` Andy Lutomirski
2013-08-15 22:18                           ` Dave Chinner
2013-08-15 22:18                             ` Dave Chinner
2013-08-15 22:26                             ` Andy Lutomirski
2013-08-16  0:14                               ` Dave Chinner
2013-08-16  0:21                                 ` Andy Lutomirski
2013-08-16 22:02                         ` J. Bruce Fields
2013-08-16 22:02                           ` J. Bruce Fields
2013-08-16 23:18                           ` Andy Lutomirski
2013-08-16 23:18                             ` Andy Lutomirski
2013-08-18 20:17                             ` J. Bruce Fields
2013-08-18 20:17                               ` J. Bruce Fields
2013-08-19 22:17                 ` J. Bruce Fields
2013-08-19 22:17                   ` J. Bruce Fields
2013-08-19 22:29                   ` Andy Lutomirski
2013-08-19 22:29                     ` Andy Lutomirski
2013-08-15 15:14           ` Dave Hansen
2013-08-15 15:14             ` Dave Hansen
2013-08-15  0:24 ` Dave Chinner
2013-08-15  0:24   ` Dave Chinner
2013-08-15  2:24   ` Andi Kleen
2013-08-15  2:24     ` Andi Kleen
2013-08-15  4:29     ` Dave Chinner [this message]
2013-08-15  4:29       ` Dave Chinner
2013-08-15 15:36       ` Dave Hansen
2013-08-15 15:36         ` Dave Hansen
2013-08-15 15:09   ` Dave Hansen
2013-08-15 15:05 ` Theodore Ts'o
2013-08-15 17:45   ` Dave Hansen
2013-08-15 17:45     ` Dave Hansen
2013-08-15 19:31     ` Theodore Ts'o
2013-08-15 19:31       ` Theodore Ts'o

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