From: Avi Kivity <avi@redhat.com>
To: John Leach <john@brightbox.co.uk>
Cc: Stefan Hajnoczi <stefanha@gmail.com>,
kvm@vger.kernel.org, Anthony Liguori <anthony@codemonkey.ws>
Subject: Re: bad O_DIRECT read and write performance with small block sizes with virtio
Date: Tue, 03 Aug 2010 17:44:37 +0300 [thread overview]
Message-ID: <4C582B55.2030209@redhat.com> (raw)
In-Reply-To: <1280846424.13790.26.camel@dogen>
On 08/03/2010 05:40 PM, John Leach wrote:
>
> dd if=/dev/mapper/zero of=/dev/null bs=8k count=1000000 iflag=direct
> 8192000000 bytes (8.2 GB) copied, 3.46529 s, 2.4 GB/s
>
> dd if=/dev/mapper/zero of=/dev/null bs=8k count=1000000
> 8192000000 bytes (8.2 GB) copied, 5.5741 s, 1.5 GB/s
>
> dd is just using read.
>
What's /dev/mapper/zero? A real volume or a zero target?
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2010-08-03 14:44 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-02 17:15 bad O_DIRECT read and write performance with small block sizes with virtio John Leach
2010-08-02 17:46 ` Anthony Liguori
2010-08-02 20:50 ` Stefan Hajnoczi
2010-08-03 6:35 ` Dor Laor
2010-08-03 14:52 ` John Leach
2010-08-03 14:40 ` John Leach
2010-08-03 14:44 ` Avi Kivity [this message]
2010-08-03 14:57 ` John Leach
2010-08-03 16:14 ` Avi Kivity
2010-08-04 12:38 ` Stefan Hajnoczi
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