Re: [Intel-gfx] [PATCH 19/46] drm/i915/guc: Assign contexts in parent-child relationship consecutive guc_ids

Matthew Brost
2021-08-09T19:03:15Z

On Mon, Aug 09, 2021 at 05:31:38PM +0200, Daniel Vetter wrote:
> On Tue, Aug 03, 2021 at 03:29:16PM -0700, 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.
> >
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > ---
> > drivers/gpu/drm/i915/gt/intel_context.h | 6 +
> > drivers/gpu/drm/i915/gt/intel_reset.c | 3 +-
> > drivers/gpu/drm/i915/gt/uc/intel_guc.h | 7 +-
> > .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 222 ++++++++++++------
> > .../i915/gt/uc/intel_guc_submission_types.h | 10 +
> > 5 files changed, 179 insertions(+), 69 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
> > index c208691fc87d..7ce3b3d2edb7 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_context.h
> > +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> > @@ -54,6 +54,12 @@ static inline bool intel_context_is_parent(struct intel_context *ce)
> > return !!ce->guc_number_children;
> > }
> >
> > +static inline struct intel_context *
> > +intel_context_to_parent(struct intel_context *ce)
> > +{
> > + return intel_context_is_child(ce) ? ce->parent : ce;
> > +}
> > +
> > void intel_context_bind_parent_child(struct intel_context *parent,
> > struct intel_context *child);
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> > index ea763138197f..c3d4baa1b2b8 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> > @@ -849,6 +849,7 @@ static void reset_finish(struct intel_gt *gt, intel_engine_mask_t awake)
> >
> > static void nop_submit_request(struct i915_request *request)
> > {
> > + struct intel_context *ce = intel_context_to_parent(request->context);
> > RQ_TRACE(request, "-EIO\n");
> >
> > /*
> > @@ -857,7 +858,7 @@ static void nop_submit_request(struct i915_request *request)
> > * this for now.
> > */
> > if (intel_engine_uses_guc(request->engine))
> > - intel_guc_decr_num_rq_not_ready(request->context);
> > + intel_guc_decr_num_rq_not_ready(ce);
> >
> > request = i915_request_mark_eio(request);
> > if (request) {
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.h b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> > index c0c60ccabfa4..30a0f364db8f 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.h
> > @@ -24,6 +24,7 @@ struct __guc_ads_blob;
> >
> > enum {
> > GUC_SUBMIT_ENGINE_SINGLE_LRC,
> > + GUC_SUBMIT_ENGINE_MULTI_LRC,
> > GUC_SUBMIT_ENGINE_MAX
> > };
> >
> > @@ -59,8 +60,10 @@ struct intel_guc {
> > struct ida guc_ids;
> > u32 num_guc_ids;
> > u32 max_guc_ids;
> > - struct list_head guc_id_list_no_ref;
> > - struct list_head guc_id_list_unpinned;
> > + unsigned long *guc_ids_bitmap;
> > +#define MAX_GUC_ID_ORDER (order_base_2(MAX_ENGINE_INSTANCE + 1))
> > + struct list_head guc_id_list_no_ref[MAX_GUC_ID_ORDER + 1];
> > + struct list_head guc_id_list_unpinned[MAX_GUC_ID_ORDER + 1];
>
> Random new global lists definitely need kerneldoc about what is on them,
> how they're linked, what their lifetime rules are and what locks we're
> holding.
>
> Leaving this all to reviews to figure out, and worse, future readers of
> your code, is not kind.
>

Got it.

> > spinlock_t destroy_lock; /* protects list / worker */
> > struct list_head destroyed_contexts;
> > 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 f23dd716723f..afb9b4bb8971 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> > @@ -169,6 +169,15 @@ static void clr_guc_ids_exhausted(struct guc_submit_engine *gse)
> > clear_bit(GSE_STATE_GUC_IDS_EXHAUSTED, &gse->flags);
> > }
> >
> > +/*
> > + * We reserve 1/16 of the guc_ids for multi-lrc as these need to be contiguous
>
> I think it'd be good to put down the reason here for why. Is this a
> requirement of the guc interface, or just an artifact of our current
> implementation? In the latter case also explain what exactly the
> contstraint is (but honestly I can't think of much reasons for that)

Multi-lrc guc_ids need to be sequential between the parent and children
- this is a requirement of the GuC submission interface. Can explicitly
state that here.

Matt

> -Daniel
>
> > + * and a different allocation algorithm is used (bitmap vs. ida). We believe the
> > + * number of multi-lrc contexts in use should be low and 1/16 should be
> > + * sufficient. Minimum of 32 ids for multi-lrc.
> > + */
> > +#define NUMBER_MULTI_LRC_GUC_ID(guc) \
> > + ((guc)->num_guc_ids / 16 > 32 ? (guc)->num_guc_ids / 16 : 32)
> > +
> > /*
> > * Below is a set of functions which control the GuC scheduling state which do
> > * not require a lock as all state transitions are mutually exclusive. i.e. It
> > @@ -405,16 +414,10 @@ static inline void decr_context_blocked(struct intel_context *ce)
> > ce->guc_state.sched_state -= SCHED_STATE_BLOCKED;
> > }
> >
> > -static inline struct intel_context *
> > -to_parent(struct intel_context *ce)
> > -{
> > - return intel_context_is_child(ce) ? ce->parent : ce;
> > -}
> > -
> > static inline struct intel_context *
> > request_to_scheduling_context(struct i915_request *rq)
> > {
> > - return to_parent(rq->context);
> > + return intel_context_to_parent(rq->context);
> > }
> >
> > static inline bool context_guc_id_invalid(struct intel_context *ce)
> > @@ -1436,7 +1439,7 @@ static void destroy_worker_func(struct work_struct *w);
> > */
> > int intel_guc_submission_init(struct intel_guc *guc)
> > {
> > - int ret;
> > + int ret, i;
> >
> > if (guc_submission_initialized(guc))
> > return 0;
> > @@ -1448,9 +1451,13 @@ int intel_guc_submission_init(struct intel_guc *guc)
> > xa_init_flags(&guc->context_lookup, XA_FLAGS_LOCK_IRQ);
> >
> > spin_lock_init(&guc->contexts_lock);
> > - INIT_LIST_HEAD(&guc->guc_id_list_no_ref);
> > - INIT_LIST_HEAD(&guc->guc_id_list_unpinned);
> > + for (i = 0; i < MAX_GUC_ID_ORDER + 1; ++i) {
> > + INIT_LIST_HEAD(&guc->guc_id_list_no_ref[i]);
> > + INIT_LIST_HEAD(&guc->guc_id_list_unpinned[i]);
> > + }
> > ida_init(&guc->guc_ids);
> > + guc->guc_ids_bitmap =
> > + bitmap_zalloc(NUMBER_MULTI_LRC_GUC_ID(guc), GFP_KERNEL);
> >
> > spin_lock_init(&guc->destroy_lock);
> >
> > @@ -1476,6 +1483,8 @@ void intel_guc_submission_fini(struct intel_guc *guc)
> >
> > i915_sched_engine_put(sched_engine);
> > }
> > +
> > + bitmap_free(guc->guc_ids_bitmap);
> > }
> >
> > static inline void queue_request(struct i915_sched_engine *sched_engine,
> > @@ -1499,11 +1508,13 @@ static inline void queue_request(struct i915_sched_engine *sched_engine,
> > static bool too_many_guc_ids_not_ready(struct guc_submit_engine *gse,
> > struct intel_context *ce)
> > {
> > - u32 available_guc_ids, guc_ids_consumed;
> > struct intel_guc *guc = gse->sched_engine.private_data;
> > + u32 available_guc_ids = intel_context_is_parent(ce) ?
> > + NUMBER_MULTI_LRC_GUC_ID(guc) :
> > + guc->num_guc_ids - NUMBER_MULTI_LRC_GUC_ID(guc);
> > + u32 guc_ids_consumed = atomic_read(&gse->num_guc_ids_not_ready);
> >
> > - available_guc_ids = guc->num_guc_ids;
> > - guc_ids_consumed = atomic_read(&gse->num_guc_ids_not_ready);
> > + GEM_BUG_ON(intel_context_is_child(ce));
> >
> > if (TOO_MANY_GUC_IDS_NOT_READY(available_guc_ids, guc_ids_consumed)) {
> > set_and_update_guc_ids_exhausted(gse);
> > @@ -1517,17 +1528,26 @@ static void incr_num_rq_not_ready(struct intel_context *ce)
> > {
> > struct guc_submit_engine *gse = ce_to_gse(ce);
> >
> > + GEM_BUG_ON(intel_context_is_child(ce));
> > + GEM_BUG_ON(!intel_context_is_parent(ce) &&
> > + ce->guc_number_children);
> > +
> > if (!atomic_fetch_add(1, &ce->guc_num_rq_not_ready))
> > - atomic_inc(&gse->num_guc_ids_not_ready);
> > + atomic_add(ce->guc_number_children + 1,
> > + &gse->num_guc_ids_not_ready);
> > }
> >
> > void intel_guc_decr_num_rq_not_ready(struct intel_context *ce)
> > {
> > struct guc_submit_engine *gse = ce_to_gse(ce);
> >
> > + GEM_BUG_ON(intel_context_is_child(ce));
> > +
> > if (atomic_fetch_add(-1, &ce->guc_num_rq_not_ready) == 1) {
> > GEM_BUG_ON(!atomic_read(&gse->num_guc_ids_not_ready));
> > - atomic_dec(&gse->num_guc_ids_not_ready);
> > +
> > + atomic_sub(ce->guc_number_children + 1,
> > + &gse->num_guc_ids_not_ready);
> > }
> > }
> >
> > @@ -1579,20 +1599,42 @@ static void guc_submit_request(struct i915_request *rq)
> >
> > spin_unlock_irqrestore(&sched_engine->lock, flags);
> >
> > - intel_guc_decr_num_rq_not_ready(rq->context);
> > + intel_guc_decr_num_rq_not_ready(request_to_scheduling_context(rq));
> > }
> >
> > -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->guc_ids, 0,
> > - guc->num_guc_ids, 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->guc_ids_bitmap,
> > + NUMBER_MULTI_LRC_GUC_ID(guc),
> > + order_base_2(ce->guc_number_children
> > + + 1));
> > + else
> > + ret = ida_simple_get(&guc->guc_ids,
> > + NUMBER_MULTI_LRC_GUC_ID(guc),
> > + guc->num_guc_ids, GFP_KERNEL |
> > + __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
> > + if (unlikely(ret < 0))
> > + return ret;
> > +
> > + ce->guc_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->guc_ids, ce->guc_id);
> > + if (intel_context_is_parent(ce))
> > + bitmap_release_region(guc->guc_ids_bitmap, ce->guc_id,
> > + order_base_2(ce->guc_number_children
> > + + 1));
> > + else
> > + ida_simple_remove(&guc->guc_ids, ce->guc_id);
> > clr_lrc_desc_registered(guc, ce->guc_id);
> > set_context_guc_id_invalid(ce);
> > }
> > @@ -1604,6 +1646,8 @@ static void release_guc_id(struct intel_guc *guc, struct intel_context *ce)
> > {
> > unsigned long flags;
> >
> > + GEM_BUG_ON(intel_context_is_child(ce));
> > +
> > spin_lock_irqsave(&guc->contexts_lock, flags);
> > __release_guc_id(guc, ce);
> > spin_unlock_irqrestore(&guc->contexts_lock, flags);
> > @@ -1618,54 +1662,93 @@ static void release_guc_id(struct intel_guc *guc, struct intel_context *ce)
> > * schedule disable H2G + a deregister H2G.
> > */
> > static struct list_head *get_guc_id_list(struct intel_guc *guc,
> > + u8 number_children,
> > bool unpinned)
> > {
> > + GEM_BUG_ON(order_base_2(number_children + 1) > MAX_GUC_ID_ORDER);
> > +
> > if (unpinned)
> > - return &guc->guc_id_list_unpinned;
> > + return &guc->guc_id_list_unpinned[order_base_2(number_children + 1)];
> > else
> > - return &guc->guc_id_list_no_ref;
> > + return &guc->guc_id_list_no_ref[order_base_2(number_children + 1)];
> > }
> >
> > -static int steal_guc_id(struct intel_guc *guc, bool unpinned)
> > +static int steal_guc_id(struct intel_guc *guc, struct intel_context *ce,
> > + bool unpinned)
> > {
> > - struct intel_context *ce;
> > - int guc_id;
> > - struct list_head *guc_id_list = get_guc_id_list(guc, unpinned);
> > + struct intel_context *cn;
> > + u8 number_children = ce->guc_number_children;
> >
> > lockdep_assert_held(&guc->contexts_lock);
> > + GEM_BUG_ON(intel_context_is_child(ce));
> >
> > - if (!list_empty(guc_id_list)) {
> > - ce = list_first_entry(guc_id_list,
> > - struct intel_context,
> > - guc_id_link);
> > + do {
> > + struct list_head *guc_id_list =
> > + get_guc_id_list(guc, number_children, unpinned);
> >
> > - /* Ensure context getting stolen in expected state */
> > - GEM_BUG_ON(atomic_read(&ce->guc_id_ref));
> > - GEM_BUG_ON(context_guc_id_invalid(ce));
> > - GEM_BUG_ON(context_guc_id_stolen(ce));
> > + if (!list_empty(guc_id_list)) {
> > + u8 cn_o2, ce_o2 =
> > + order_base_2(ce->guc_number_children + 1);
> >
> > - list_del_init(&ce->guc_id_link);
> > - guc_id = ce->guc_id;
> > - clr_context_registered(ce);
> > + cn = list_first_entry(guc_id_list,
> > + struct intel_context,
> > + guc_id_link);
> > + cn_o2 = order_base_2(cn->guc_number_children + 1);
> > +
> > + /*
> > + * Corner case where a multi-lrc context steals a guc_id
> > + * from another context that has more guc_id that itself.
> > + */
> > + if (cn_o2 != ce_o2) {
> > + bitmap_release_region(guc->guc_ids_bitmap,
> > + cn->guc_id,
> > + cn_o2);
> > + bitmap_allocate_region(guc->guc_ids_bitmap,
> > + ce->guc_id,
> > + ce_o2);
> > + }
> > +
> > + /* Ensure context getting stolen in expected state */
> > + GEM_BUG_ON(atomic_read(&cn->guc_id_ref));
> > + GEM_BUG_ON(context_guc_id_invalid(cn));
> > + GEM_BUG_ON(context_guc_id_stolen(cn));
> > + GEM_BUG_ON(ce_to_gse(ce) != ce_to_gse(cn));
> > +
> > + list_del_init(&cn->guc_id_link);
> > + ce->guc_id = cn->guc_id;
> > +
> > + /*
> > + * If stealing from the pinned list, defer invalidating
> > + * the guc_id until the retire workqueue processes this
> > + * context.
> > + */
> > + clr_context_registered(cn);
> > + if (!unpinned) {
> > + GEM_BUG_ON(ce_to_gse(cn)->stalled_context);
> > + ce_to_gse(cn)->stalled_context =
> > + intel_context_get(cn);
> > + set_context_guc_id_stolen(cn);
> > + } else {
> > + set_context_guc_id_invalid(cn);
> > + }
> > +
> > + return 0;
> > + }
> >
> > /*
> > - * If stealing from the pinned list, defer invalidating
> > - * the guc_id until the retire workqueue processes this
> > - * context.
> > + * When using multi-lrc we search the guc_id_lists with the
> > + * least amount of guc_ids required first but will consume a
> > + * block larger of guc_ids if necessary. 2x the children always
> > + * moves you two the next list.
> > */
> > - if (!unpinned) {
> > - GEM_BUG_ON(ce_to_gse(ce)->stalled_context);
> > + if (!number_children ||
> > + order_base_2(number_children + 1) == MAX_GUC_ID_ORDER)
> > + break;
> >
> > - ce_to_gse(ce)->stalled_context = intel_context_get(ce);
> > - set_context_guc_id_stolen(ce);
> > - } else {
> > - set_context_guc_id_invalid(ce);
> > - }
> > + number_children *= 2;
> > + } while (true);
> >
> > - return guc_id;
> > - } else {
> > - return -EAGAIN;
> > - }
> > + return -EAGAIN;
> > }
> >
> > enum { /* Return values for pin_guc_id / assign_guc_id */
> > @@ -1674,17 +1757,18 @@ enum { /* Return values for pin_guc_id / assign_guc_id */
> > NEW_GUC_ID_ENABLED = 2,
> > };
> >
> > -static int assign_guc_id(struct intel_guc *guc, u16 *out, bool tasklet)
> > +static int assign_guc_id(struct intel_guc *guc, struct intel_context *ce,
> > + bool tasklet)
> > {
> > int ret;
> >
> > lockdep_assert_held(&guc->contexts_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, true);
> > - if (ret >= 0) {
> > - *out = ret;
> > + ret = steal_guc_id(guc, ce, true);
> > + if (!ret) {
> > ret = NEW_GUC_ID_DISABLED;
> > } else if (ret < 0 && tasklet) {
> > /*
> > @@ -1692,15 +1776,18 @@ static int assign_guc_id(struct intel_guc *guc, u16 *out, bool tasklet)
> > * enabled if guc_ids are exhausted and we are submitting
> > * from the tasklet.
> > */
> > - ret = steal_guc_id(guc, false);
> > - if (ret >= 0) {
> > - *out = ret;
> > + ret = steal_guc_id(guc, ce, false);
> > + if (!ret)
> > ret = NEW_GUC_ID_ENABLED;
> > - }
> > }
> > - } else {
> > - *out = ret;
> > - ret = SAME_GUC_ID;
> > + }
> > +
> > + if (!(ret < 0) && intel_context_is_parent(ce)) {
> > + struct intel_context *child;
> > + int i = 1;
> > +
> > + for_each_child(ce, child)
> > + child->guc_id = ce->guc_id + i++;
> > }
> >
> > return ret;
> > @@ -1713,6 +1800,7 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce,
> > int ret = 0;
> > unsigned long flags, tries = PIN_GUC_ID_TRIES;
> >
> > + GEM_BUG_ON(intel_context_is_child(ce));
> > GEM_BUG_ON(atomic_read(&ce->guc_id_ref));
> >
> > try_again:
> > @@ -1724,7 +1812,7 @@ static int pin_guc_id(struct intel_guc *guc, struct intel_context *ce,
> > }
> >
> > if (context_guc_id_invalid(ce)) {
> > - ret = assign_guc_id(guc, &ce->guc_id, tasklet);
> > + ret = assign_guc_id(guc, ce, tasklet);
> > if (unlikely(ret < 0))
> > goto out_unlock;
> > }
> > @@ -1770,6 +1858,7 @@ static void unpin_guc_id(struct intel_guc *guc,
> > 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)))
> > return;
> > @@ -1781,7 +1870,8 @@ static void unpin_guc_id(struct intel_guc *guc,
> >
> > if (!context_guc_id_invalid(ce) && !context_guc_id_stolen(ce) &&
> > !atomic_read(&ce->guc_id_ref)) {
> > - struct list_head *head = get_guc_id_list(guc, unpinned);
> > + struct list_head *head =
> > + get_guc_id_list(guc, ce->guc_number_children, unpinned);
> >
> > list_add_tail(&ce->guc_id_link, head);
> > }
> > diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission_types.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission_types.h
> > index 7069b7248f55..a5933e07bdd2 100644
> > --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission_types.h
> > +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission_types.h
> > @@ -22,6 +22,16 @@ struct guc_virtual_engine {
> > /*
> > * Object which encapsulates the globally operated on i915_sched_engine +
> > * the GuC submission state machine described in intel_guc_submission.c.
> > + *
> > + * Currently we have two instances of these per GuC. One for single-lrc and one
> > + * for multi-lrc submission. We split these into two submission engines as they
> > + * can operate in parallel allowing a blocking condition on one not to affect
> > + * the other. i.e. guc_ids are statically allocated between these two submission
> > + * modes. One mode may have guc_ids exhausted which requires blocking while the
> > + * other has plenty of guc_ids and can make forward progres.
> > + *
> > + * In the future if different submission use cases arise we can simply
> > + * instantiate another of these objects and assign it to the context.
> > */
> > struct guc_submit_engine {
> > struct i915_sched_engine sched_engine;
> > --
> > 2.28.0
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch