Re: [Xen-devel] [Hackathon minutes] PV block improvements

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.06.13 at 17:57, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Sat, 2013-06-22 at 09:11 +0200, Roger Pau Monnà wrote:
>> Also, grant_copy takes
>> the grant lock, so when scaling to a large number of domains there's
>> going to be contention around this lock.
> 
> Does grant copy really take the lock for the duration of the copy,
> preventing any other grant ops from the source and/or target domain?
> 
> If true then that sounds like an area which is ripe for optimisation!
> 
> However I am hopeful that you are mistaken... __acquire_grant_for_copy()
> takes the grant lock while it pins the entry into the active grant entry
> list and not for the actual duration of the copy (and likewise
> __release_grant_for-copy). I hope Jan can confirm this!

Yes, that's how I recall it works since the removal of the per-domain
lock uses from those paths.

Jan

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