Re: [PATCH v3 1/5] xen: introduce two different max_nr_dom0/domU_grant_frames parameters

[David Vrabel <david.vrabel@citrix.com>]

On 08/10/14 17:59, Stefano Stabellini wrote:
> On Wed, 8 Oct 2014, David Vrabel wrote:
>> On 08/10/14 17:01, Stefano Stabellini wrote:
>>> On Wed, 8 Oct 2014, David Vrabel wrote:
>>>> On 08/10/14 14:00, Stefano Stabellini wrote:
>>>>> Remove max_nr_grant_frames, both variable and preprocessor symbol.
>>>>> Introduce two global variables max_nr_dom0_grant_frames and
>>>>> max_nr_domU_grant_frames, separately configurable via the Xen command line
>>>>> option "gnttab_max_nr_frames".
>>>>
>>>> Why?  I can't think of a sensible use case for this and you don't list
>>>> one.  dom0 doesn't really use grants so its current number grant frames
>>>> is usually 1 so it doesn't seem useful to restrict it differently.
>>>
>>> See the recent discussion with Jan:
>>>
>>> http://marc.info/?l=xen-devel&m=141260825209210
>>
>> I still don't see a use case.  Either:
>>
>> a) dom0 is the driver domain and doesn't need a large number of grants.
>>
>> or
>>
>> b) dom0 has a frontend driver, then the driver domain will have to scan
>> dom0's grant table thus dom0's grant table must be sized the same as domUs.
> 
> I don't have an opinion on this, so I'll leave it up to you and Jan to
> come to an agreement.

I don't feel strongly on this so I'll defer to Jan.

David