On 10/05/2016 10:43 AM, Nikolay Shirokovskiy wrote:
adding cc
On 26.09.2016 13:36, Nikolay Shirokovskiy wrote:
>
> 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
>
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the problem is that current modes are a little bit adhoc.
The describe non-trivial combination of 3 parameters,
which could be tuned on/off independently. That is why
it would be more clear to use the approach with separate
flags.
Den