From mboxrd@z Thu Jan  1 00:00:00 1970
From: Badari Pulavarty <pbadari@us.ibm.com>
Subject: Re: [RFC] vhost-blk implementation
Date: Tue, 23 Mar 2010 07:48:44 -0700
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References: <1269306023.7931.72.camel@badari-desktop> <4BA81685.9060809@codemonkey.ws> <4BA81D2F.1020405@us.ibm.com> <4BA820AE.7090803@codemonkey.ws> <4BA82C5B.8010808@us.ibm.com> <4BA89256.4030100@redhat.com>
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Cc: Anthony Liguori <anthony@codemonkey.ws>, kvm@vger.kernel.org
To: Avi Kivity <avi@redhat.com>
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Avi Kivity wrote:
> On 03/23/2010 04:50 AM, Badari Pulavarty wrote:
>> Anthony Liguori wrote:
>>> On 03/22/2010 08:45 PM, Badari Pulavarty wrote:
>>>> Anthony Liguori wrote:
>>>>> On 03/22/2010 08:00 PM, Badari Pulavarty wrote:
>>>>>> Forgot to CC: KVM list earlier
>>>>>
>>>>>
>>>>> These virtio results are still with a 2.6.18 kernel with no aio, 
>>>>> right?
>>>> Results are on 2.6.33-rc8-net-next kernel. But not using AIO.
>>>
>>> Can you try with aio and cache=none?
>>
>> aio-native,cache=none
>>
>> # time dd if=/dev/vda of=/dev/null bs=128k iflag=direct
>> 640000+0 records in
>> 640000+0 records out
>> 83886080000 bytes (84 GB) copied, 470.588 seconds, 170 MB/s
>>
>
> You're effectively killing readahead with this.  

Yes. cache=none, aio=native will force it hit the disk all the time. We 
loose all the benefits of
readahead.
> Please use fio with a sequential pattern, queue depth > 1.
>
Will do.

Thanks,
Badari