Re: [Intel-gfx] [PATCH 10/28] drm/i915: Change shrink ordering to use locking around unbinding.

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 21-10-2021 om 18:12 schreef Matthew Auld:
> On Thu, 21 Oct 2021 at 11:37, Maarten Lankhorst
> <maarten.lankhorst@linux.intel.com> wrote:
>> Call drop_pages with the gem object lock held, instead of the other
>> way around. This will allow us to drop the vma bindings with the
>> gem object lock held.
>>
>> We plan to require the object lock for unpinning in the future,
>> and this is an easy target.
>>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> Reviewed-by: Niranjana Vishwanathapura <niranjana.vishwanathapura@intel.com>
>> ---
>>  drivers/gpu/drm/i915/gem/i915_gem_shrinker.c | 42 ++++++++++----------
>>  1 file changed, 22 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
>> index af3eb7fd951d..d3f29a66cb36 100644
>> --- a/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_shrinker.c
>> @@ -36,8 +36,8 @@ static bool can_release_pages(struct drm_i915_gem_object *obj)
>>         return swap_available() || obj->mm.madv == I915_MADV_DONTNEED;
>>  }
>>
>> -static bool unsafe_drop_pages(struct drm_i915_gem_object *obj,
>> -                             unsigned long shrink, bool trylock_vm)
>> +static int drop_pages(struct drm_i915_gem_object *obj,
>> +                      unsigned long shrink, bool trylock_vm)
>>  {
>>         unsigned long flags;
>>
>> @@ -208,26 +208,28 @@ i915_gem_shrink(struct i915_gem_ww_ctx *ww,
>>
>>                         spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
>>
>> -                       err = 0;
>> -                       if (unsafe_drop_pages(obj, shrink, trylock_vm)) {
>> -                               /* May arrive from get_pages on another bo */
>> -                               if (!ww) {
>> -                                       if (!i915_gem_object_trylock(obj))
>> -                                               goto skip;
>> -                               } else {
>> -                                       err = i915_gem_object_lock(obj, ww);
>> -                                       if (err)
>> -                                               goto skip;
>> -                               }
>> -
>> -                               if (!__i915_gem_object_put_pages(obj)) {
>> -                                       try_to_writeback(obj, shrink);
>> -                                       count += obj->base.size >> PAGE_SHIFT;
>> -                               }
>> -                               if (!ww)
>> -                                       i915_gem_object_unlock(obj);
>> +                       /* May arrive from get_pages on another bo */
>> +                       if (!ww) {
>> +                               if (!i915_gem_object_trylock(obj))
>> +                                       goto skip;
>> +                       } else {
>> +                               err = i915_gem_object_lock(obj, ww);
>> +                               if (err)
>> +                                       goto skip;
>>                         }
>>
>> +                       if (drop_pages(obj, shrink, trylock_vm) &&
>> +                           !__i915_gem_object_put_pages(obj)) {
>> +                               try_to_writeback(obj, shrink);
>> +                               count += obj->base.size >> PAGE_SHIFT;
>> +                       }
>> +
>> +                       if (dma_resv_test_signaled(obj->base.resv, true))
>> +                               dma_resv_add_excl_fence(obj->base.resv, NULL);
> I assume we want to rip out resv_prune here in the series, or
> something? Instead of randomly adding this back here.
Oh yeah, this hunk can be removed safely. It's stale and shouldn't be here. :)
>> +
>> +                       if (!ww)
>> +                               i915_gem_object_unlock(obj);
>> +
>>                         scanned += obj->base.size >> PAGE_SHIFT;
>>  skip:
>>                         i915_gem_object_put(obj);
>> --
>> 2.33.0
>>