Re: [Xen-users] HVM on 3.2 kernel hdd speed issue

[Joseph Glanville <joseph.glanville@xxxxxxxxxxxxxx>]

On 2 April 2012 22:49, Mario <mario@xxxxxxxxxxxxxx> wrote:
> On 04/02/2012 01:55 PM, Heiko Wundram wrote:
>>
>> Am 02.04.2012 13:33, schrieb Mario:
>>>
>>> On 04/02/2012 12:19 PM, Heiko Wundram wrote:
>>>>
>>>> Windows, of course, does not natively support PVonHVM in any way (except
>>>> when using corresponding drivers to enable that), so if you get
>>>> excessively slower I/O-speeds on "fully" virtualized Linux DomUs than
>>>> you do on Windows DomUs which _don't_ have the corresponding PV-drivers
>>>> installed, something else is amiss here; it'd help if you could describe
>>>> your setup in a little more detail.
>>>>
>>>
>>> Why are we still on PVonHVM subject? I do not want that, I want
>>> regular HVM to work with linux domU's the same way it works with
>>> windows domU's. I don't have the luxury to install custom drivers on
>>> some domU's, so there is no point in trying to force me to use PVonHVM
>>> because i can't.
>>> So, anyone else please? :-)
>>
>>
>> Read my last paragraph again, please: Linux fully virtualized DomUs
>> (which use the corresponding NIC and disk emulation as implemented by
>> qemu) shouldn't perform any different than a Windows DomU,
>> I/O-performance wise, as both of them use the same infrastructure in
>> Dom0 to do I/O (qemu process). You're saying that they are different,
>> I/O-wise, so: please be a little more concrete _what_ the problem is
>> that you're seeing. We don't have crystal balls handy, sorry.
>>
>
> Its actualy quite simple, here is an example: Windows hvm domU disk io on my
> test server is ~60MB/s (sequential read or write). Linux HVM guests (using
> same config file template) on the same server gives ~10MB/s (sequential read
> or write), i tried pretty much everything, from tuning scheduler to changing
> kernel. I am not sure what to do with it, other then roll back to kernel
> 2.6.34 on my dom0.

Hieko and myself have told you what to do to get decent performance.
Some examples of fully setup PVonHVM guests are available on my file mirror.
http://mirror.orionvm.com.au

Unless you use the PV drivers there isn't really a whole lot more I
can do for you.

I can't explain why performance would differ under 2.6.34 vs 3.2.
This makes no sense as qemu-dm runs in userspace. You would have had to make
some changes to the toolstack for this performance to differ.

>
>
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