[Intel-gfx] [PATCH 16/40] drm/i915: Pull scheduling under standalone lock

[Tvrtko Ursulin]

On 25/09/2018 10:10, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2018-09-25 10:01:21)
>>
>> On 25/09/2018 09:19, Chris Wilson wrote:
>>> Quoting Tvrtko Ursulin (2018-09-24 12:19:39)
>>>>
>>>> On 19/09/2018 20:55, Chris Wilson wrote:
>>>>> diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
>>>>> new file mode 100644
>>>>> index 000000000000..910ac7089596
>>>>> --- /dev/null
>>>>> +++ b/drivers/gpu/drm/i915/i915_scheduler.c
>>>>> @@ -0,0 +1,377 @@
>>>>> +/*
>>>>> + * SPDX-License-Identifier: MIT
>>>>> + *
>>>>> + * Copyright © 2018 Intel Corporation
>>>>> + */
>>>>> +
>>>>> +#include <linux/mutex.h>
>>>>> +
>>>>> +#include "i915_drv.h"
>>>>> +#include "i915_request.h"
>>>>> +#include "i915_scheduler.h"
>>>>> +
>>>>> +static DEFINE_SPINLOCK(schedule_lock);
>>>>
>>>> Any good excuses to not put it into device private straight away?
>>>
>>> It can't be per-device, since it will need to be global across devices
>>> as the dependency chains may cross devices and we will want to choose an
>>> optimal order globally. That's my goal here, at least.
>>>
>>> At some point, the horror of scalability vs priority inversion must then
>>> be tackled. (But for now, I'd rather have priority inheritance and start
>>> from a position of good qos and build scalability on top.)
>>
>> Hm.. questionable that we would want to break the isolation between
>> devices, but more importantly too early to know. Struct mutex this
>> replaces is certainly per device so I'd expect would had been an
>> argument to keep that organisation. At least not change two things at
>> once. Never mind, it is not a very important detail at the moment.
> 
> The intention was to someday handle even priorities across dmabuf. Using
> dfs_link was a mere convenience to not have to have a fancy allocation
> scheme here and to avoid some ingenuity for list protection. The lack
> of priority inheritance across devices is a user visible problem today
> for optimus/hybrid systems :(

Maybe, but solving that needs a protocol between drivers and I don't 
think a shared private lock in i915 is an interesting step towards it.

Regards,

Tvrtko