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Re: [Qemu-devel] is it possible to use a disk with multiple iothreads ?
From: |
Alexandre DERUMIER |
Subject: |
Re: [Qemu-devel] is it possible to use a disk with multiple iothreads ? |
Date: |
Mon, 27 Oct 2014 15:13:11 +0100 (CET) |
>>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.
----- Mail original -----
De: "Stefan Hajnoczi" <address@hidden>
À: "Alexandre DERUMIER" <address@hidden>
Cc: "qemu-devel" <address@hidden>, "josh durgin" <address@hidden>
Envoyé: Lundi 27 Octobre 2014 14:19:58
Objet: Re: is it possible to use a disk with multiple iothreads ?
On Fri, Oct 24, 2014 at 03:39:52PM +0200, Alexandre DERUMIER wrote:
> >>Regarding Ceph, do you know why it burns a lot of CPU?
>
> I'm currently doing some perfs to find why is so huge.
>
> One thing is that qemu+ qemu rbd block driver + librbd seem to use 2-3x more
> cpu, than passing krbd /dev/rbd0 from host to qemu.
> Don't known yet if the problem is librbd or qemu rbd block driver.
That's very interesting! Please keep Josh and me in CC when you want to
discuss the results.
Stefan
report.txt.gz
Description: GNU Zip compressed data