RE: [Xen-users] Asynchronous IO

["Priya, PM" <pm.priya@xxxxxx>]

Hi,

Thanks for your response. Even I got 52MB/sec when I tried to do IO with
buffer size 1 MB. But if I try to do IO with buffer size 512 Bytes, I am
getting 0.032 MB which is 67 IOPs which is not the expected result. Have
you tried the asynchronosu IO with different IO sizes??

I am sure I am using right version of MPT driver in Domain 0. Moreover
the same driver performs better if I do synchronous IO in Domain 0. I am
confused.

Thanks,
Priya. 

-----Original Message-----
From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Andrew
Warfield
Sent: Thursday, September 08, 2005 11:11 PM
To: Priya PM
Cc: Ian Pratt; ian.pratt@xxxxxxxxxxxx; Xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] Asynchronous IO

Hi Priya,

   I regularly use libaio in domain zero as a user-space backend for
other domains and am able to saturate a MPT fusion at about 60MB/s
without trying too hard.  I seem to remember seeing a comment about a
recent performance drop on the linux-aio list, possibly from 2.6.11 to
2.6.12, you might want to take a peek at that.  Also, are you sure that
your XenLinux dom0 kernel has your disk driver in it, and that it isn't
deferring to a less-efficient means of accessing the disk?

a.

On 9/9/05, Priya PM <pmpriya@xxxxxxxxx> wrote:
> Hi,
>   
> I tried the same operation with unstable version too. I have changed 
> the IO scheduler to atropos and tried. But no use. I always get the
same results.
> Has anyone checked the Asynchronous IO path using libaio? 
>   
> It would be very much helpful if you can give me some ideas to proceed

> further,
>   
> Thanks,
> Priya.
> 
>  
>  
> On 9/8/05, Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx> wrote: 
> > > I have installed Xen on Linux 2.6.11.10 and i am trying to do 
> > > Asynchronous Direct IO on SAS drives. The application which does 
> > > the asynchronous direct io on SAS drive is running on Domain 0. 
> > > Actually the IOPs what i get for a 512Bytes IO size is 67, but if 
> > > i do the same operation on Linux 2.6.11.10 native kernel, i get 
> > > 267 IOPs.Can anyone tell me why this huge differnece? Am i missing

> > > something? In the current setup on Xen, if i do Synchronous IO, 
> > > then i am getting 265 IOPs which is expected. So i am wondering 
> > > why Asynchronous IO should behave this way? Is there any reason??
> > 
> > That's odd. You might want to try the -unstable tree. I know Andy 
> > has used AIO just fine on -unstable.
> > 
> > Ian
> > 
> 
>  
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> 
>

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