Re: [Intel-gfx] [PATCH 10/26] drm/i915/guc: Assign contexts in parent-child relationship consecutive guc_ids

John Harrison
2021-10-13T19:11:47Z

On 10/13/2021 11:03, Matthew Brost wrote:
> On Fri, Oct 08, 2021 at 09:40:43AM -0700, John Harrison wrote:
>> On 10/7/2021 18:21, Matthew Brost wrote:
>>> On Thu, Oct 07, 2021 at 03:03:04PM -0700, John Harrison wrote:
>>>> On 10/4/2021 15:06, Matthew Brost wrote:
>>>>> Assign contexts in parent-child relationship consecutive guc_ids. This
>>>>> is accomplished by partitioning guc_id space between ones that need to
>>>>> be consecutive (1/16 available guc_ids) and ones that do not (15/16 of
>>>>> available guc_ids). The consecutive search is implemented via the bitmap
>>>>> API.
>>>>>
>>>>> This is a precursor to the full GuC multi-lrc implementation but aligns
>>>>> to how GuC mutli-lrc interface is defined - guc_ids must be consecutive
>>>>> when using the GuC multi-lrc interface.
>>>>>
>>>>> v2:
>>>>> (Daniel Vetter)
>>>>> - Explicitly state why we assign consecutive guc_ids
>>>>> v3:
>>>>> (John Harrison)
>>>>> - Bring back in spin lock
>>>>>
>>>>> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
>>>>> ---
>>>>> drivers/gpu/drm/i915/gt/uc/intel_guc.h | 6 +-
>>>>> .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 104 ++++++++++++++----
>>>>> 2 files changed, 86 insertions(+), 24 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
>>>>> index 25a598e2b6e8..a9f4ec972bfb 100644
>>>>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
>>>>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
>>>>> @@ -76,9 +76,13 @@ struct intel_guc {
>>>>> */
>>>>> spinlock_t lock;
>>>>> /**
>>>>> - * @guc_ids: used to allocate new guc_ids
>>>>> + * @guc_ids: used to allocate new guc_ids, single-lrc
>>>>> */
>>>>> struct ida guc_ids;
>>>>> + /**
>>>>> + * @guc_ids_bitmap: used to allocate new guc_ids, multi-lrc
>>>>> + */
>>>>> + unsigned long *guc_ids_bitmap;
>>>>> /**
>>>>> * @guc_id_list: list of intel_context with valid guc_ids but no
>>>>> * refs
>>>>> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>>>> index 1f2809187513..79e7732e83b2 100644
>>>>> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>>>> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
>>>>> @@ -128,6 +128,16 @@ guc_create_virtual(struct intel_engine_cs **siblings, unsigned int count);
>>>>> #define GUC_REQUEST_SIZE 64 /* bytes */
>>>>> +/*
>>>>> + * We reserve 1/16 of the guc_ids for multi-lrc as these need to be contiguous
>>>>> + * per the GuC submission interface. A different allocation algorithm is used
>>>>> + * (bitmap vs. ida) between multi-lrc and single-lrc hence the reason to
>>>>> + * partition the guc_id space. We believe the number of multi-lrc contexts in
>>>>> + * use should be low and 1/16 should be sufficient. Minimum of 32 guc_ids for
>>>>> + * multi-lrc.
>>>>> + */
>>>>> +#define NUMBER_MULTI_LRC_GUC_ID (GUC_MAX_LRC_DESCRIPTORS / 16)
>>>>> +
>>>>> /*
>>>>> * Below is a set of functions which control the GuC scheduling state which
>>>>> * require a lock.
>>>>> @@ -1206,6 +1216,11 @@ int intel_guc_submission_init(struct intel_guc *guc)
>>>>> INIT_WORK(&guc->submission_state.destroyed_worker,
>>>>> destroyed_worker_func);
>>>>> + guc->submission_state.guc_ids_bitmap =
>>>>> + bitmap_zalloc(NUMBER_MULTI_LRC_GUC_ID, GFP_KERNEL);
>>>>> + if (!guc->submission_state.guc_ids_bitmap)
>>>>> + return -ENOMEM;
>>>>> +
>>>>> return 0;
>>>>> }
>>>>> @@ -1217,6 +1232,7 @@ void intel_guc_submission_fini(struct intel_guc *guc)
>>>>> guc_lrc_desc_pool_destroy(guc);
>>>>> guc_flush_destroyed_contexts(guc);
>>>>> i915_sched_engine_put(guc->sched_engine);
>>>>> + bitmap_free(guc->submission_state.guc_ids_bitmap);
>>>>> }
>>>>> static inline void queue_request(struct i915_sched_engine *sched_engine,
>>>>> @@ -1268,18 +1284,43 @@ static void guc_submit_request(struct i915_request *rq)
>>>>> spin_unlock_irqrestore(&sched_engine->lock, flags);
>>>>> }
>>>>> -static int new_guc_id(struct intel_guc *guc)
>>>>> +static int new_guc_id(struct intel_guc *guc, struct intel_context *ce)
>>>>> {
>>>>> - return ida_simple_get(&guc->submission_state.guc_ids, 0,
>>>>> - GUC_MAX_LRC_DESCRIPTORS, GFP_KERNEL |
>>>>> - __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
>>>>> + int ret;
>>>>> +
>>>>> + GEM_BUG_ON(intel_context_is_child(ce));
>>>>> +
>>>>> + if (intel_context_is_parent(ce))
>>>>> + ret = bitmap_find_free_region(guc->submission_state.guc_ids_bitmap,
>>>>> + NUMBER_MULTI_LRC_GUC_ID,
>>>>> + order_base_2(ce->parallel.number_children
>>>>> + + 1));
>>>>> + else
>>>>> + ret = ida_simple_get(&guc->submission_state.guc_ids,
>>>>> + NUMBER_MULTI_LRC_GUC_ID,
>>>>> + GUC_MAX_LRC_DESCRIPTORS,
>>>>> + GFP_KERNEL | __GFP_RETRY_MAYFAIL |
>>>>> + __GFP_NOWARN);
>>>>> + if (unlikely(ret < 0))
>>>>> + return ret;
>>>>> +
>>>>> + ce->guc_id.id = ret;
>>>>> + return 0;
>>>>> }
>>>>> static void __release_guc_id(struct intel_guc *guc, struct intel_context *ce)
>>>>> {
>>>>> + GEM_BUG_ON(intel_context_is_child(ce));
>>>>> +
>>>>> if (!context_guc_id_invalid(ce)) {
>>>>> - ida_simple_remove(&guc->submission_state.guc_ids,
>>>>> - ce->guc_id.id);
>>>>> + if (intel_context_is_parent(ce))
>>>>> + bitmap_release_region(guc->submission_state.guc_ids_bitmap,
>>>>> + ce->guc_id.id,
>>>>> + order_base_2(ce->parallel.number_children
>>>>> + + 1));
>>>> There was a discussion on the previous revision about adding a BUG_ON to
>>>> ensure that number_children cannot change between the bitmap alloc and the
>>>> bitmap release. I'm not seeing the new BUG_ON mentioned in this patch.
>>>>
>>> I thought you meant to add a BUG_ON to ensure before we release a region
>>> / id it is occupied? I looked in both the bitmap API and ida API and
>>> neither have a function that checks if region / id is occupied so can't
>>> really add a BUG_ON for that.
>>>
>>> How much you add BUG_ON to ensure the number of children canoot change
>>> between alloc and release? I don't follow how that would work.
>>>
>>> Matt
>> I was thinking that where number_children is modified, you have a
>> BUG_ON(guc_id_is_valid). That would ensure that the release has to match the
>> alloc. Hmm, you already have a BUG_ON about the parent/child not being
>> pinned in intel_context_bind_parent_child(), which I guess covers it because
>> you shouldn't have a guc_id if you aren't pinned, right? And that is the
>> only function which can modify number_children, yes? So maybe it's all good?
>>
> I think we are all good.
We are all awesome ;)

Reviewed-by: John Harrison <John.C.Harrison@Intel.com>

> Matt
>
>> John.
>>
>>>> John.
>>>>
>>>>
>>>>> + else
>>>>> + ida_simple_remove(&guc->submission_state.guc_ids,
>>>>> + ce->guc_id.id);
>>>>> reset_lrc_desc(guc, ce->guc_id.id);
>>>>> set_context_guc_id_invalid(ce);
>>>>> }
>>>>> @@ -1296,49 +1337,64 @@ static void release_guc_id(struct intel_guc *guc, struct intel_context *ce)
>>>>> spin_unlock_irqrestore(&guc->submission_state.lock, flags);
>>>>> }
>>>>> -static int steal_guc_id(struct intel_guc *guc)
>>>>> +static int steal_guc_id(struct intel_guc *guc, struct intel_context *ce)
>>>>> {
>>>>> - struct intel_context *ce;
>>>>> - int guc_id;
>>>>> + struct intel_context *cn;
>>>>> lockdep_assert_held(&guc->submission_state.lock);
>>>>> + GEM_BUG_ON(intel_context_is_child(ce));
>>>>> + GEM_BUG_ON(intel_context_is_parent(ce));
>>>>> if (!list_empty(&guc->submission_state.guc_id_list)) {
>>>>> - ce = list_first_entry(&guc->submission_state.guc_id_list,
>>>>> + cn = list_first_entry(&guc->submission_state.guc_id_list,
>>>>> struct intel_context,
>>>>> guc_id.link);
>>>>> - GEM_BUG_ON(atomic_read(&ce->guc_id.ref));
>>>>> - GEM_BUG_ON(context_guc_id_invalid(ce));
>>>>> + GEM_BUG_ON(atomic_read(&cn->guc_id.ref));
>>>>> + GEM_BUG_ON(context_guc_id_invalid(cn));
>>>>> + GEM_BUG_ON(intel_context_is_child(cn));
>>>>> + GEM_BUG_ON(intel_context_is_parent(cn));
>>>>> - list_del_init(&ce->guc_id.link);
>>>>> - guc_id = ce->guc_id.id;
>>>>> + list_del_init(&cn->guc_id.link);
>>>>> + ce->guc_id = cn->guc_id;
>>>>> spin_lock(&ce->guc_state.lock);
>>>>> - clr_context_registered(ce);
>>>>> + clr_context_registered(cn);
>>>>> spin_unlock(&ce->guc_state.lock);
>>>>> - set_context_guc_id_invalid(ce);
>>>>> - return guc_id;
>>>>> + set_context_guc_id_invalid(cn);
>>>>> +
>>>>> + return 0;
>>>>> } else {
>>>>> return -EAGAIN;
>>>>> }
>>>>> }
>>>>> -static int assign_guc_id(struct intel_guc *guc, u16 *out)
>>>>> +static int assign_guc_id(struct intel_guc *guc, struct intel_context *ce)
>>>>> {
>>>>> int ret;
>>>>> lockdep_assert_held(&guc->submission_state.lock);
>>>>> + GEM_BUG_ON(intel_context_is_child(ce));
>>>>> - ret = new_guc_id(guc);
>>>>> + ret = new_guc_id(guc, ce);
>>>>> if (unlikely(ret < 0)) {
>>>>> - ret = steal_guc_id(guc);
>>>>> + if (intel_context_is_parent(ce))
>>>>> + return -ENOSPC;
>>>>> +
>>>>> + ret = steal_guc_id(guc, ce);
>>>>> if (ret < 0)
>>>>> return ret;
>>>>> }
>>>>> - *out = ret;
>>>>> + if (intel_context_is_parent(ce)) {
>>>>> + struct intel_context *child;
>>>>> + int i = 1;
>>>>> +
>>>>> + for_each_child(ce, child)
>>>>> + child->guc_id.id = ce->guc_id.id + i++;
>>>>> + }
>>>>> +
>>>>> return 0;
>>>>> }
>>>>> @@ -1356,7 +1412,7 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce)
>>>>> might_lock(&ce->guc_state.lock);
>>>>> if (context_guc_id_invalid(ce)) {
>>>>> - ret = assign_guc_id(guc, &ce->guc_id.id);
>>>>> + ret = assign_guc_id(guc, ce);
>>>>> if (ret)
>>>>> goto out_unlock;
>>>>> ret = 1; /* Indidcates newly assigned guc_id */
>>>>> @@ -1398,8 +1454,10 @@ static void unpin_guc_id(struct intel_guc *guc, struct intel_context *ce)
>>>>> unsigned long flags;
>>>>> GEM_BUG_ON(atomic_read(&ce->guc_id.ref) < 0);
>>>>> + GEM_BUG_ON(intel_context_is_child(ce));
>>>>> - if (unlikely(context_guc_id_invalid(ce)))
>>>>> + if (unlikely(context_guc_id_invalid(ce) ||
>>>>> + intel_context_is_parent(ce)))
>>>>> return;
>>>>> spin_lock_irqsave(&guc->submission_state.lock, flags);