Re: [Xen-devel] 2.4.29-xenU VBD performance (problem)

[Nivedita Singhvi <niv@xxxxxxxxxx>]

Ian Pratt wrote:

> > But, under domU (2.4.29-xenU), using that same lvm-volume as 
> > VBD, I only get around 
> > 10 - 12 MB/sec write performance measured in the same way.
>
> That's very odd -- I see virtually no loss of throughput in a domU.
>
> However, 100MB isn't really enough to get a decent measure as its likely to all 
> still be in memory -- sync doesn't do what you think. I usually do measurements 
> using a transfer size of 10x the memory of the system.
>
> A couple of other things to try if you still experience poor peformance:
>   * use a 2.6 domU
>   * use a raw partition rather than LVM
>
> We do most of our testing using 2.6 for everything, so its possible there a 
> weird 2.4 domU to 2.6 dom0 performance bug.
Right. And to some extent, comparing 2.4 to 2.6 is
a bit of an apples to oranges comparison. There are
other differences in the kernel path - not just the
virtual block driver coming out of domU.

thanks,
Nivedita



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