Re: [Qemu-devel] [Qemu-block] [PATCH 0/3] mirror: Fix guest responsiveness during bitmap scan

[Alexandre DERUMIER <aderumier@odiso.com>]

>>Thinking about this again, I doubt
>>that lengthening the duration with a hardcoded value benifits everyone; and
>>before Alexandre's reply on old server/slow disks

With 1ms sleep, I can reproduce the hang 100% with a fast cpu (xeon e5 v3 3,1ghz) and source raw file on nfs.


----- Mail original -----
De: "Fam Zheng" <famz@redhat.com>
À: "Stefan Hajnoczi" <stefanha@gmail.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>, "qemu-devel" <qemu-devel@nongnu.org>, qemu-block@nongnu.org
Envoyé: Vendredi 10 Juillet 2015 08:43:50
Objet: Re: [Qemu-devel] [Qemu-block] [PATCH 0/3] mirror: Fix guest responsiveness during bitmap scan

On Thu, 07/09 14:02, Stefan Hajnoczi wrote: 
> This patch only converts the mirror block job to use the new relax 
> function. The other block jobs (stream, backup, commit) are still using 
> a 0 ns delay and are therefore broken. They should probably be 
> converted in the same series. 

That's because they all can be perfectly mitigated by setting a reasonable 
"speed" that matchs the host horsepower. Thinking about this again, I doubt 
that lengthening the duration with a hardcoded value benifits everyone; and 
before Alexandre's reply on old server/slow disks, I don't recall any report, 
because the coroutines would already yield often enough, when waiting for IO to 
complete. So I am not sure whether they're broken in practice. 

Fam