[libvirt] [PATCH 1/2] conf: add disk cache tuning parameters after qemu

[Nikolay Shirokovskiy]

On 26.09.2016 13:04, Peter Krempa wrote:
> On Mon, Sep 26, 2016 at 12:15:42 +0300, Nikolay Shirokovskiy wrote:
>> On 26.09.2016 12:01, Peter Krempa wrote:
> 
> [...]
> 
>> 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.
> 
> Well, if there are useful combinations we can add them to the existing
> cache setting.
> 
>> So I decided to provide new possibilities just as qemu does - keep
>> old parameter and use new ones to tune over.
> 
> I don't think this is a good idea at all. It's very qemu specific and
> can be mapped to existing elements.
> 
> Peter
> 

Well up until now libvirt cache settings are exactly the same as the qemu ones. I thought
it would be inconsistent to intordocuce new name and then map internallly to 
qemu. Another point is that these 3 parameters are probably not that qemu specific.

Nikolay