Re: [libvirt] [PATCH 1/2] conf: add disk cache tuning parameters after qemu
On 26.09.2016 12:01, Peter Krempa wrote:
On Mon, Sep 26, 2016 at 11:43:58 +0300, Nikolay Shirokovskiy wrote:
> xml example:
>
> <disk ...>
> <cachetune writeback='on' direct='off'
no_flush='on'/>
Aren't writeback and direct mutually exclusive?
> </disk>
What's wrong with
<disk ...>
<driver ... cache=''>?
See https://libvirt.org/formatdomain.html#elementsDisks
This commit message really does not describe your motivation for the
addition.
Sorry, I forget to write down the motivation.
Internally qemu uses 3 orthogonal flags to configure disk cache. They
are exposed in interface too quite long time ago (29c4e2b). All-in-one
cache parameter that libvirt uses now do not provide all possible
values (5 vs 8). For example absent combination of direct + no flush (no sync)
is useful to speed up tests.
So I decided to provide new possibilities just as qemu does - keep
old parameter and use new ones to tune over.