From: Stefan Hajnoczi <stefanha@gmail.com>
To: "Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>
Cc: Qemu-development List <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] QEMU throughput is down with SMP
Date: Thu, 30 Sep 2010 10:13:56 +0100 [thread overview]
Message-ID: <AANLkTimDeFQcnC+0OAb0XgkYrSKNNmkUASRQJRifY_SL@mail.gmail.com> (raw)
In-Reply-To: <4CA3DEC7.5070609@linux.vnet.ibm.com>
On Thu, Sep 30, 2010 at 1:50 AM, Venkateswararao Jujjuri (JV)
<jvrao@linux.vnet.ibm.com> wrote:
> Code: Mainline QEMU (git://git.qemu.org/qemu.git)
> Machine: LS21 blade.
> Disk: Local disk through VirtIO.
> Did not select any cache option. Defaulting to writethrough.
>
> Command tested:
> 3 parallel instances of : dd if=/dev/zero of=/pmnt/my_pw bs=4k count=100000
>
> QEMU with smp=1
> 19.3 MB/s + 19.2 MB/s + 18.6 MB/s = 57.1 MB/s
>
> QEMU with smp=4
> 15.3 MB/s + 14.1 MB/s + 13.6 MB/s = 43.0 MB/s
>
> Is this expected?
Did you configure with --enable-io-thread?
Also, try using dd oflag=direct to eliminate effects introduced by the
guest page cache and really hit the disk.
Stefan
next prev parent reply other threads:[~2010-09-30 9:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-30 0:50 [Qemu-devel] QEMU throughput is down with SMP Venkateswararao Jujjuri (JV)
2010-09-30 9:13 ` Stefan Hajnoczi [this message]
2010-09-30 19:19 ` Venkateswararao Jujjuri (JV)
2010-10-01 8:41 ` Stefan Hajnoczi
2010-10-01 13:38 ` Ryan Harper
2010-10-01 15:04 ` Venkateswararao Jujjuri (JV)
2010-10-01 15:09 ` Stefan Hajnoczi
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