From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
To: Zhi Yong Wu <zwu.kernel@gmail.com>
Cc: kwolf@redhat.com, Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>,
aliguro@us.ibm.com, qemu-devel@nongnu.org, ryanh@us.ibm.com
Subject: Re: [Qemu-devel] Why qemu write/rw speed is so low?
Date: Tue, 13 Sep 2011 08:14:19 +0100 [thread overview]
Message-ID: <20110913071419.GA14528@stefanha-thinkpad.localdomain> (raw)
In-Reply-To: <CAEH94LjJ-U7HcKZ=4-nLdvuuTea8UN9amw=4E_-SG--n54=mPA@mail.gmail.com>
On Tue, Sep 13, 2011 at 10:52:44AM +0800, Zhi Yong Wu wrote:
> This is real log when fio issued with bs=128K and bps=1000000(block
> I/O throttling):
I would use 1024 * 1024 instead of 1000000 as the throughput limit.
10^5 is not a multiple of 512 bytes and is not a nice value in KB/s
(976.5625).
>
> 8,2 0 1 0.000000000 24332 A WS 79958528 + 256 <-
> (253,2) 71830016
256 blocks = 256 * 512 bytes = 128 KB per request. We know the maximum
request size from Linux is 128 KB so this makes sense.
> Throughput (R/W): 0KiB/s / 482KiB/s
What throughput do you get without I/O throttling? Either I/O
throttling is limiting too aggressively here or the physical disk is the
bottleneck (I double that since the write throughput value is very low).
We need to compare against the throughput when throttling is not
enabled.
Stefan
next prev parent reply other threads:[~2011-09-13 7:59 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-09 9:44 [Qemu-devel] Why qemu write/rw speed is so low? Zhi Yong Wu
2011-09-09 10:38 ` Stefan Hajnoczi
2011-09-09 13:48 ` Zhi Yong Wu
2011-09-09 13:54 ` Stefan Hajnoczi
2011-09-09 14:04 ` Kevin Wolf
2011-09-09 15:27 ` Stefan Hajnoczi
2011-09-11 13:32 ` Christoph Hellwig
2011-09-09 14:09 ` Zhi Yong Wu
2011-09-13 2:38 ` Zhi Yong Wu
2011-09-13 2:52 ` Zhi Yong Wu
2011-09-13 7:14 ` Stefan Hajnoczi [this message]
2011-09-13 9:25 ` Zhi Yong Wu
2011-09-13 10:14 ` Stefan Hajnoczi
2011-09-13 10:27 ` Zhi Yong Wu
2011-09-14 2:42 ` Zhi Yong Wu
2011-09-14 14:17 ` Stefan Hajnoczi
2011-09-15 9:04 ` Zhi Yong Wu
2011-09-13 7:15 ` Stefan Hajnoczi
2011-09-13 8:31 ` Zhi Yong Wu
2011-09-13 8:49 ` Stefan Hajnoczi
2011-09-13 8:54 ` Zhi Yong Wu
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