Re: [Qemu-devel] Slow PXE boot in qemu.git (fast in qemu-kvm.git)

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-04-11 21:15, Luiz Capitulino wrote:
> On Mon, 11 Apr 2011 13:00:32 -0600
> Alex Williamson <alex.williamson@redhat.com> wrote:
> 
>> On Mon, 2011-04-11 at 15:35 -0300, Luiz Capitulino wrote:
>>> On Fri, 08 Apr 2011 19:50:57 -0500
>>> Anthony Liguori <anthony@codemonkey.ws> wrote:
>>>
>>>> On 04/08/2011 06:25 PM, Luiz Capitulino wrote:
>>>>> Hi there,
>>>>>
>>>>> Summary:
>>>>>
>>>>>   - PXE boot in qemu.git (HEAD f124a41) is quite slow, more than 5 minutes. Got
>>>>>     the problem with e1000, virtio and rtl8139. However, pcnet *works* (it's
>>>>>     as fast as qemu-kvm.git)
>>>>>
>>>>>   - PXE boot in qemu-kvm.git (HEAD df85c051) is fast, less than a minute. Tried
>>>>>     with e1000, virtio and rtl8139 (I don't remember if I tried with pcnet)
>>>>>
>>
>> I was having this problem too, but I think it's because I forgot to
>> build qemu with --enable-io-thread, which is the default for qemu-kvm.
>> Can you re-configure and build with that and see if it's fast?  Thanks,
> 
> Yes, nice catch, it's faster with I/O thread enabled, even seem faster
> than qemu-kvm.git.

What's the performance under qemu-kvm with -no-kvm-irqchip?

> 
> So, does this have to be fixed w/o I/O thread?

If it's most probably an architectural deficit of non-io-thread mode, I
would say let it rest in peace. But maybe it points to a generic issues
that is just magnified by non-threaded mode.

Jan


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