From: Eric Sandeen <sandeen@redhat.com>
To: Norbert Preining <preining@logic.at>
Cc: "Ted Ts'o" <tytso@mit.edu>,
"linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>
Subject: Re: Ext4 slow on links
Date: Wed, 20 Jun 2012 09:07:23 -0500 [thread overview]
Message-ID: <4FE1D91B.8020707@redhat.com> (raw)
In-Reply-To: <20120620051844.GA7829@gamma.logic.tuwien.ac.at>
On 6/20/12 12:18 AM, Norbert Preining wrote:
> Hi Eric,
>
> On Di, 19 Jun 2012, Eric Sandeen wrote:
>> blktrace of the actions would show you something interesting as well.
>
> I tried to understand the output, but didn't get any information
> that tells me something.
>
> I rebooted into single user mode, started blktrace on sda, then run
> time ls -l /..../dir/with/links/ >/dev/null, stopped the blktrace.
>
> Then I run blkparse and btt etc to generate a variety of data.
...
>
> I don't know if that shows anything of interest, but if you need more,
> and want to waste a bit of time looking at the data, I have uploaded
> everything created into
> http://www.logic.at/people/preining/BlkParse.tar.gz
Here are the overall stats:
Total (sda):
Reads Queued: 8,864, 35,456KiB Writes Queued: 90, 7,980KiB
Read Dispatches: 8,864, 35,456KiB Write Dispatches: 49, 7,980KiB
Reads Requeued: 0 Writes Requeued: 0
Reads Completed: 8,864, 35,456KiB Writes Completed: 59, 7,980KiB
Read Merges: 0, 0KiB Write Merges: 41, 164KiB
IO unplugs: 81 Timer unplugs: 0
so almost all reads, and no read merges; almost 35 megabytes read and every
one was a small 4k IO.
It's doing about 120 seeks/second. I'm a little surprised that there was no read
merging...
Let me think about this. :)
-Eric
next prev parent reply other threads:[~2012-06-20 14:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-20 0:20 Ext4 slow on links Norbert Preining
2012-06-20 2:19 ` Ted Ts'o
2012-06-20 3:38 ` Norbert Preining
2012-06-20 3:57 ` Eric Sandeen
2012-06-20 4:01 ` Norbert Preining
2012-06-20 5:18 ` Norbert Preining
2012-06-20 14:07 ` Eric Sandeen [this message]
2012-06-20 19:35 ` Eric Sandeen
2012-06-21 2:28 ` Norbert Preining
2012-06-21 4:05 ` Eric Sandeen
2012-06-21 4:50 ` Norbert Preining
2012-06-21 5:18 ` Andreas Dilger
2012-06-21 6:55 ` Norbert Preining
2012-06-22 9:53 ` Bernd Schubert
2012-06-22 14:08 ` Ted Ts'o
2012-06-20 3:15 ` Eric Sandeen
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