Re: [Xen-users] Asynchronous IO

[Andrew Warfield <andrew.warfield@xxxxxxxxx>]

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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