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

Maarten Lankhorst
2021-10-22T11:05:03Z

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
>>