Re: [PATCHv13 1/2] gnttab: use per-VCPU maptrack free lists

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

On 16/06/15 07:27, Jan Beulich wrote:
>>>> On 15.06.15 at 16:47, <david.vrabel@citrix.com> wrote:
>> @@ -57,7 +58,7 @@ integer_param("gnttab_max_frames", max_grant_frames);
>>   * New options allow to set max_maptrack_frames and
>>   * map_grant_table_frames independently.
>>   */
>> -#define DEFAULT_MAX_MAPTRACK_FRAMES 256
>> +#define DEFAULT_MAX_MAPTRACK_FRAMES 1024
> 
> This should be undone by patch 2 now, too, or not be done here
> in the first place. I anyway wonder - also because both patches
> basically re-write __get_maptrack_handle() as well as the change
> back to the first come first serve model here - whether folding the
> second patch into this one wouldn't be better (albeit I realize that
> this would cause an authorship conflict).

We need to increase DEFAULT_MAX_MAPTRACK_FRAMES to at least 512 since
the structure is now twice as big.

We also want to avoid the slow steal path where possible so I think the
extra doubling to account for unbalanced usage is still useful.  Even
with 1024 frames this is still only 4 MiB which seems fine to me.

I would prefer to keep the steal patch separate since it's a
self-contained extra bit.

David