From: Theodore Ts'o <tytso@mit.edu>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>, Jan Kara <jack@suse.cz>,
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 15:31:22 -0400 [thread overview]
Message-ID: <20130815193122.GA19536@thunk.org> (raw)
In-Reply-To: <520D13A5.2070808@linux.intel.com>
On Thu, Aug 15, 2013 at 10:45:09AM -0700, Dave Hansen wrote:
>
> I _believe_ this is because the block allocation is occurring during the
> warmup, even in those numbers I posted previously. will-it-scale forks
> things off early and the tests spend most of their time in those while
> loops. Each "page fault handled" (the y-axis) is a trip through the
> while loop, *not* a call to testcase().
Ah, OK. Sorry, I misinterpreted what was going on.
So basically, what we have going on in the test is (a) we're bumping
i_version and/or mtime, and (b) the munmap() implies an msync(), so
writeback is happening in the background concurrently with the write
page faults, and we may be (actually, almost certainly) seeing some
interference between the writeback and the page_mkwrite operations.
That implies that if you redid the test using a ramdisk, which will
significantly speed up the writeback and overhead caused by the
journal transactions for the metadata updates, the results might very
well be different.
Cheers,
- Ted
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prev parent reply other threads:[~2013-08-15 19:31 UTC|newest]
Thread overview: 40+ 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 19:43 ` Theodore Ts'o
2013-08-14 20:50 ` Dave Hansen
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 6:01 ` Dave Chinner
2013-08-15 6:14 ` Andy Lutomirski
2013-08-15 6:18 ` David Lang
2013-08-15 6:28 ` Andy Lutomirski
2013-08-15 7:11 ` Dave Chinner
2013-08-15 7:45 ` Jan Kara
2013-08-15 21:28 ` Dave Chinner
2013-08-15 21:31 ` Andy Lutomirski
2013-08-15 21:39 ` Dave Chinner
2013-08-19 23:23 ` David Lang
2013-08-19 23:31 ` Andy Lutomirski
2013-08-15 15:17 ` Andy Lutomirski
2013-08-15 21:37 ` Dave Chinner
2013-08-15 21:43 ` Andy Lutomirski
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 23:18 ` Andy Lutomirski
2013-08-18 20:17 ` J. Bruce Fields
2013-08-19 22:17 ` J. Bruce Fields
2013-08-19 22:29 ` Andy Lutomirski
2013-08-15 15:14 ` Dave Hansen
2013-08-15 0:24 ` Dave Chinner
2013-08-15 2:24 ` Andi Kleen
2013-08-15 4:29 ` Dave Chinner
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 19:31 ` Theodore Ts'o [this message]
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