[Mesa-dev] [PATCH 0/8] Gallium & RadeonSI optimization for Ryzen CPUs

[Michel Dänzer]

On 2018-09-10 9:02 p.m., Marek Olšák wrote:
> On Mon, Sep 10, 2018 at 10:45 AM, Michel Dänzer <michel at daenzer.net> wrote:
>> On 2018-09-07 9:01 p.m., Marek Olšák wrote:
>>> On Fri, Sep 7, 2018 at 11:04 AM, Michel Dänzer <michel at daenzer.net> wrote:
>>>> On 2018-09-07 4:31 p.m., Marek Olšák wrote:
>>>>> On Fri, Sep 7, 2018, 4:34 AM Michel Dänzer <michel at daenzer.net> wrote:
>>>>>> On 2018-09-06 10:56 p.m., Axel Davy wrote:
>>>>>>
>>>>>>> I fear if we begin to do the work manually, there won't be interest to
>>>>>>> do that in the kernel,
>>>>>>> and thus all applications will need to include such core pinning code to
>>>>>>> have good performance when
>>>>>>> multithreaded.
>>>>>>
>>>>>> I'm also a bit worried that this solution could result in multiple
>>>>>> processes contending for the same set of CPU cores, while other cores
>>>>>> might be underused, which could result in worse overall system performance.
>>>>>
>>>>> [...]
>>>>
>>>> In the worst case, all processes using OpenGL (or at least their OpenGL
>>>> related threads, but that usually includes the main thread) could end up
>>>> restricted to the same 4 cores, leaving up to 28 cores underused.
>>>
>>> 4C/4T used to be a standard and certainly enough for gaming. 4C/8T
>>> used to be luxury before Ryzen, which is now the CCX. We should be
>>> fine with 4 cores.
>>
>> Sounds like "640K of memory ought to be enough for anybody"...
>>
>>
>> Anyway, per reports on IRC, the core pinning can hurt even individual
>> applications, e.g. blender. I like your idea of a driconf option, but it
>> should be disabled by default, and only enabled for apps where it's
>> known safe and beneficial in practice.
> 
> Before we do anything, we can be discuss it with Blender developers [...]

What would there be to discuss with them? They're doing nothing wrong.
The problem is that Mesa is trying to do the kernel scheduler's job,
using APIs intended for system administration tools, not low-level
libraries.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer