Re: [PATCH] i915/pmu: Wire GuC backend to per-client busyness

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 16/06/2022 23:13, Nerlige Ramappa, Umesh wrote:
> From: John Harrison <John.C.Harrison@xxxxxxxxx>
>
> GuC provides engine_id and last_switch_in ticks for an active context in
> the pphwsp. The context image provides a 32 bit total ticks which is the
> accumulated by the context (a.k.a. context[CTX_TIMESTAMP]). This
> information is used to calculate the context busyness as follows:
>
> If the engine_id is valid, then busyness is the sum of accumulated total
> ticks and active ticks. Active ticks is calculated with current gt time
> as reference.
>
> If engine_id is invalid, busyness is equal to accumulated total ticks.
>
> Since KMD (CPU) retrieves busyness data from 2 sources - GPU and GuC, a
> potential race was highlighted in an earlier review that can lead to
> double accounting of busyness. While the solution to this is a wip,
> busyness is still usable for platforms running GuC submission.
>
> v2: (Tvrtko)
> - Use COPS_RUNTIME_ACTIVE_TOTAL
> - Add code comment for the race
> - Undo local variables initializations
>
> v3:
> - Add support for virtual engines based on
>    https://patchwork.freedesktop.org/series/105227/
>
> Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
> ---
>   drivers/gpu/drm/i915/gt/intel_context.c       | 12 +++-
>   drivers/gpu/drm/i915/gt/intel_context.h       |  6 +-
>   drivers/gpu/drm/i915/gt/intel_context_types.h |  6 ++
>   drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h   |  5 ++
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 65 ++++++++++++++++++-
>   drivers/gpu/drm/i915/i915_drm_client.c        |  6 +-
>   6 files changed, 89 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
> index 4070cb5711d8..4a84146710e0 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.c
> +++ b/drivers/gpu/drm/i915/gt/intel_context.c
> @@ -576,16 +576,24 @@ void intel_context_bind_parent_child(struct intel_context *parent,
>   	child->parallel.parent = parent;
>   }
>   
> -u64 intel_context_get_total_runtime_ns(const struct intel_context *ce)
> +u64 intel_context_get_total_runtime_ns(struct intel_context *ce)
>   {
>   	u64 total, active;
>   
> +	if (ce->ops->update_stats)
> +		ce->ops->update_stats(ce);
> +
>   	total = ce->stats.runtime.total;
>   	if (ce->ops->flags & COPS_RUNTIME_CYCLES)
>   		total *= ce->engine->gt->clock_period_ns;
>   
>   	active = READ_ONCE(ce->stats.active);
> -	if (active)
> +	/*
> +	 * When COPS_RUNTIME_ACTIVE_TOTAL is set for ce->cops, the backend
> +	 * already provides the total active time of the context, so skip this
> +	 * calculation when this flag is set.
> +	 */
> +	if (active && !(ce->ops->flags & COPS_RUNTIME_ACTIVE_TOTAL))
>   		active = intel_context_clock() - active;
>   
>   	return total + active;
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
> index b7d3214d2cdd..5fc7c19ab29b 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> @@ -56,7 +56,7 @@ static inline bool intel_context_is_parent(struct intel_context *ce)
>   	return !!ce->parallel.number_children;
>   }
>   
> -static inline bool intel_context_is_pinned(struct intel_context *ce);
> +static inline bool intel_context_is_pinned(const struct intel_context *ce);
>   
>   static inline struct intel_context *
>   intel_context_to_parent(struct intel_context *ce)
> @@ -116,7 +116,7 @@ static inline int intel_context_lock_pinned(struct intel_context *ce)
>    * Returns: true if the context is currently pinned for use by the GPU.
>    */
>   static inline bool
> -intel_context_is_pinned(struct intel_context *ce)
> +intel_context_is_pinned(const struct intel_context *ce)
>   {
>   	return atomic_read(&ce->pin_count);
>   }
> @@ -351,7 +351,7 @@ intel_context_clear_nopreempt(struct intel_context *ce)
>   	clear_bit(CONTEXT_NOPREEMPT, &ce->flags);
>   }
>   
> -u64 intel_context_get_total_runtime_ns(const struct intel_context *ce);
> +u64 intel_context_get_total_runtime_ns(struct intel_context *ce);
>   u64 intel_context_get_avg_runtime_ns(struct intel_context *ce);
>   
>   static inline u64 intel_context_clock(void)
> diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> index 09f82545789f..797bb4242c18 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -38,6 +38,9 @@ struct intel_context_ops {
>   #define COPS_RUNTIME_CYCLES_BIT 1
>   #define COPS_RUNTIME_CYCLES BIT(COPS_RUNTIME_CYCLES_BIT)
>   
> +#define COPS_RUNTIME_ACTIVE_TOTAL_BIT 2
> +#define COPS_RUNTIME_ACTIVE_TOTAL BIT(COPS_RUNTIME_ACTIVE_TOTAL_BIT)
> +
>   	int (*alloc)(struct intel_context *ce);
>   
>   	void (*ban)(struct intel_context *ce, struct i915_request *rq);
> @@ -55,6 +58,8 @@ struct intel_context_ops {
>   
>   	void (*sched_disable)(struct intel_context *ce);
>   
> +	void (*update_stats)(struct intel_context *ce);
> +
>   	void (*reset)(struct intel_context *ce);
>   	void (*destroy)(struct kref *kref);
>   
> @@ -146,6 +151,7 @@ struct intel_context {
>   			struct ewma_runtime avg;
>   			u64 total;
>   			u32 last;
> +			u64 start_gt_clk;
>   			I915_SELFTEST_DECLARE(u32 num_underflow);
>   			I915_SELFTEST_DECLARE(u32 max_underflow);
>   		} runtime;
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> index b3c9a9327f76..6231ad03e4eb 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> @@ -196,6 +196,11 @@ static inline u8 guc_class_to_engine_class(u8 guc_class)
>   	return guc_class_engine_class_map[guc_class];
>   }
>   
> +/* Per context engine usage stats: */
> +#define PPHWSP_GUC_CONTEXT_USAGE_STAMP_LO	(0x500 / sizeof(u32))
> +#define PPHWSP_GUC_CONTEXT_USAGE_STAMP_HI	(PPHWSP_GUC_CONTEXT_USAGE_STAMP_LO + 1)
> +#define PPHWSP_GUC_CONTEXT_USAGE_ENGINE_ID	(PPHWSP_GUC_CONTEXT_USAGE_STAMP_HI + 1)
> +
>   /* Work item for submitting workloads into work queue of GuC. */
>   struct guc_wq_item {
>   	u32 header;
> 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 5a1dfacf24ea..cbf3cbb983ce 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -378,7 +378,7 @@ static inline void set_context_guc_id_invalid(struct intel_context *ce)
>   	ce->guc_id.id = GUC_INVALID_CONTEXT_ID;
>   }
>   
> -static inline struct intel_guc *ce_to_guc(struct intel_context *ce)
> +static inline struct intel_guc *ce_to_guc(const struct intel_context *ce)
>   {
>   	return &ce->engine->gt->uc.guc;
>   }
> @@ -1323,13 +1323,16 @@ static void __update_guc_busyness_stats(struct intel_guc *guc)
>   	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
>   }
>   
> +static void __guc_context_update_clks(struct intel_context *ce);
>   static void guc_timestamp_ping(struct work_struct *wrk)
>   {
>   	struct intel_guc *guc = container_of(wrk, typeof(*guc),
>   					     timestamp.work.work);
>   	struct intel_uc *uc = container_of(guc, typeof(*uc), guc);
>   	struct intel_gt *gt = guc_to_gt(guc);
> +	struct intel_context *ce;
>   	intel_wakeref_t wakeref;
> +	unsigned long index;
>   	int srcu, ret;
>   
>   	/*
> @@ -1343,6 +1346,10 @@ static void guc_timestamp_ping(struct work_struct *wrk)
>   	with_intel_runtime_pm(&gt->i915->runtime_pm, wakeref)
>   		__update_guc_busyness_stats(guc);
>   
> +	/* adjust context stats for overflow */
> +	xa_for_each(&guc->context_lookup, index, ce)
> +		__guc_context_update_clks(ce);
> +
>   	intel_gt_reset_unlock(gt, srcu);
>   
>   	mod_delayed_work(system_highpri_wq, &guc->timestamp.work,
> @@ -1405,6 +1412,56 @@ void intel_guc_busyness_unpark(struct intel_gt *gt)
>   			 guc->timestamp.ping_delay);
>   }
>   
> +static void __guc_context_update_clks(struct intel_context *ce)
> +{
> +	struct intel_guc *guc = ce_to_guc(ce);
> +	struct intel_gt *gt = ce->engine->gt;
> +	u32 *pphwsp, last_switch, engine_id;
> +	u64 start_gt_clk, active;
> +	unsigned long flags;
> +	ktime_t unused;
> +
> +	spin_lock_irqsave(&guc->timestamp.lock, flags);
> +
> +	/*
> +	 * GPU updates ce->lrc_reg_state[CTX_TIMESTAMP] when context is switched
> +	 * out, however GuC updates PPHWSP offsets below. Hence KMD (CPU)
> +	 * relies on GuC and GPU for busyness calculations. Due to this, A
> +	 * potential race was highlighted in an earlier review that can lead to
> +	 * double accounting of busyness. While the solution to this is a wip,
> +	 * busyness is still usable for platforms running GuC submission.
> +	 */
> +	pphwsp = ((void *)ce->lrc_reg_state) - LRC_STATE_OFFSET;
> +	last_switch = READ_ONCE(pphwsp[PPHWSP_GUC_CONTEXT_USAGE_STAMP_LO]);
> +	engine_id = READ_ONCE(pphwsp[PPHWSP_GUC_CONTEXT_USAGE_ENGINE_ID]);
> +
> +	guc_update_pm_timestamp(guc, &unused);
> +
> +	if (engine_id != 0xffffffff && last_switch) {
> +		start_gt_clk = READ_ONCE(ce->stats.runtime.start_gt_clk);
> +		__extend_last_switch(guc, &start_gt_clk, last_switch);
> +		active = intel_gt_clock_interval_to_ns(gt, guc->timestamp.gt_stamp - start_gt_clk);
> +		WRITE_ONCE(ce->stats.runtime.start_gt_clk, start_gt_clk);
> +		WRITE_ONCE(ce->stats.active, active);
> +	} else {
> +		lrc_update_runtime(ce);
> +	}
> +
> +	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
> +}
> +
> +static void guc_context_update_stats(struct intel_context *ce)
> +{
> +	if (!intel_context_pin_if_active(ce)) {
> +		WRITE_ONCE(ce->stats.runtime.start_gt_clk, 0);
> +		WRITE_ONCE(ce->stats.active, 0);
> +		return;
> +	}
> +
> +	__guc_context_update_clks(ce);
> +	intel_context_unpin(ce);
> +}
> +
>   static inline bool
>   submission_disabled(struct intel_guc *guc)
>   {
> @@ -2585,6 +2642,7 @@ static void guc_context_unpin(struct intel_context *ce)
>   {
>   	struct intel_guc *guc = ce_to_guc(ce);
>   
> +	lrc_update_runtime(ce);
>   	unpin_guc_id(guc, ce);
>   	lrc_unpin(ce);
>   
> @@ -3183,6 +3241,7 @@ static void remove_from_context(struct i915_request *rq)
>   }
>   
>   static const struct intel_context_ops guc_context_ops = {
> +	.flags = COPS_RUNTIME_CYCLES | COPS_RUNTIME_ACTIVE_TOTAL,
>   	.alloc = guc_context_alloc,
>   
>   	.pre_pin = guc_context_pre_pin,
> @@ -3199,6 +3258,8 @@ static const struct intel_context_ops guc_context_ops = {
>   
>   	.sched_disable = guc_context_sched_disable,
>   
> +	.update_stats = guc_context_update_stats,
> +
>   	.reset = lrc_reset,
>   	.destroy = guc_context_destroy,
>   
> @@ -3432,6 +3493,7 @@ static int guc_virtual_context_alloc(struct intel_context *ce)
>   }
>   
>   static const struct intel_context_ops virtual_guc_context_ops = {
> +	.flags = COPS_RUNTIME_CYCLES | COPS_RUNTIME_ACTIVE_TOTAL,
>   	.alloc = guc_virtual_context_alloc,
>   
>   	.pre_pin = guc_virtual_context_pre_pin,
> @@ -3447,6 +3509,7 @@ static const struct intel_context_ops virtual_guc_context_ops = {
>   	.exit = guc_virtual_context_exit,
>   
>   	.sched_disable = guc_context_sched_disable,
> +	.update_stats = guc_context_update_stats,

There are also virtual_parent_context_ops and virtual_child_context_ops 
- which means more test coverage is needed..

Regards,

Tvrtko

>   
>   	.destroy = guc_context_destroy,
>   
> diff --git a/drivers/gpu/drm/i915/i915_drm_client.c b/drivers/gpu/drm/i915/i915_drm_client.c
> index 18d38cb59923..118db6f03f15 100644
> --- a/drivers/gpu/drm/i915/i915_drm_client.c
> +++ b/drivers/gpu/drm/i915/i915_drm_client.c
> @@ -146,11 +146,7 @@ void i915_drm_client_fdinfo(struct seq_file *m, struct file *f)
>   		   PCI_SLOT(pdev->devfn), PCI_FUNC(pdev->devfn));
>   	seq_printf(m, "drm-client-id:\t%u\n", client->id);
>   
> -	/*
> -	 * Temporarily skip showing client engine information with GuC submission till
> -	 * fetching engine busyness is implemented in the GuC submission backend
> -	 */
> -	if (GRAPHICS_VER(i915) < 8 || intel_uc_uses_guc_submission(&i915->gt0.uc))
> +	if (GRAPHICS_VER(i915) < 8)
>   		return;
>   
>   	for (i = 0; i < ARRAY_SIZE(uabi_class_names); i++)