Re: [Qemu-devel] is it possible to use a disk with multiple iothreads ?

[Alexandre DERUMIER <aderumier@odiso.com>]

>>You are missing debug information unfortunately,

Ok thanks, I'll try to add qemu debug symbols.

(I have already libc6,librbd,librados debug symbols installed)

----- Mail original -----

De: "Paolo Bonzini" <pbonzini@redhat.com>
À: "Alexandre DERUMIER" <aderumier@odiso.com>, "Stefan Hajnoczi" <stefanha@redhat.com>
Cc: "josh durgin" <josh.durgin@inktank.com>, "qemu-devel" <qemu-devel@nongnu.org>
Envoyé: Lundi 27 Octobre 2014 15:47:19
Objet: Re: is it possible to use a disk with multiple iothreads ?



On 10/27/2014 03:13 PM, Alexandre DERUMIER wrote:
>>> That's very interesting! Please keep Josh and me in CC when you want to
>>> >>discuss the results.
> Here the aggregate results (perf report details attached in this mail)
>
> + 33,02% 3974368751 kvm [kernel.kallsyms]
> + 23,66% 2847206635 kvm libc-2.13.so
> + 18,79% 2262052133 kvm librados.so.2.0.0
> + 11,04% 1328581527 kvm librbd.so.1.0.0
> + 5,87% 706713737 kvm libpthread-2.13.so
> + 3,75% 451690142 kvm kvm
> + 2,74% 329457334 kvm libstdc++.so.6.0.17
> + 0,51% 61519664 kvm [vdso] + 0,42% 50000089 kvm libglib-2.0.so.0.3200.4 + 0,15% 18119658 kvm libm-2.13.so + 0,05% 5705776 kvm librt-2.13.so + 0,00% 356625 kvm libz.so.1.
2.7
>
>
>
>
>>> >> 23,66% 2847206635 kvm libc-2.13.so
> This one is mostly malloc,free,...
>
>
> I see almost same results using fio with rbdengine on the host (outside the kvm process).
> So I think they are all mostly related to librbd.

You are missing debug information unfortunately, but the slowdown seems
to be related to futexes.

Paolo