[Intel-gfx] [PATCH 17/40] drm/i915: Priority boost for waiting clients

[Tvrtko Ursulin]

On 25/09/2018 10:00, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2018-09-24 12:29:45)
>>
>> On 19/09/2018 20:55, Chris Wilson wrote:
>>> +#define I915_PRIORITY_WAIT   ((u8)BIT(1))
>>>    #define I915_PRIORITY_NEWCLIENT     ((u8)BIT(0))
>>
>> Put a comment here explaining the priority order is reversed in the
>> internal range.
>>
>> With new client protection against being repeatedly pre-empted added in
>> a respective previous patch, I am okay that we give this a go.
> 
> Hmm, actually it is not reversed. So you would prefer new clients to
> have a small priority boost over the stalling clients (which are in
> effect under control of the user). Ok.

I thought it was reversed:

+	/* buckets sorted from highest [in slot 0] to lowest priority */
+	idx = I915_PRIORITY_MASK - (prio & I915_PRIORITY_MASK);
+	prio >>= I915_USER_PRIORITY_SHIFT;

But my two comments are not related - I just wanted a comment next to 
internal level definitions in case they are reversed. If they are not 
reversed it is fine without a comment. I guess the comment only applies 
to bucket organization, not the priority levels, that was my confusion..

It made sense to me that new clients would be more important than 
something stuck on a potentially long wait.. but I don't know, it's all 
guesswork.

Regards,

Tvrtko