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

Tvrtko Ursulin
2022-08-05T09:45:48Z

On 05/08/2022 00:21, Umesh Nerlige Ramappa wrote:
> From: John Harrison <John.C.Harrison@Intel.com>
>
> 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.
>
> Remaining work: Enable and test context busyness for
> virtual_parent_context_ops and virtual_child_context_ops.

I meant track the IGT work in the jira internally. :)

Otherwise:

Acked-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Also, can someone else please do the full review? I'm afraid with the
passage of time I forgot what little I knew about how GuC tracks this
data. :(

Some nits and questions below.

> 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/
>
> v4:
> - Update commit message with remaining work.
> - Rebase
>
> Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
> ---
> 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 654a092ed3d6..e2d70a9fdac0 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 8e2d70630c49..3d1d7436c1a4 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> @@ -58,7 +58,7 @@ 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)
> @@ -118,7 +118,7 @@ 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);
> }
> @@ -362,7 +362,7 @@ 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 04eacae1aca5..f7ff4c7d81c7 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 (*revoke)(struct intel_context *ce, struct i915_request *rq,
> @@ -56,6 +59,8 @@ 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);
>
> @@ -148,6 +153,7 @@ struct intel_context {
> struct ewma_runtime avg;
> u64 total;
> u32 last;
> + u64 start_gt_clk;

Nit - put u64 next to u64 and u32 next to u32 to avoid holes.

> 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 323b055e5db9..c7b54f1631b9 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 0d17da77e787..c9fefa254a7e 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)

This is odd since the helper now takes away constness. I can't really
figure out why the change is needed?

> {
> return &ce->engine->gt->uc.guc;
> }
> @@ -1376,13 +1376,16 @@ 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;
>
> /*
> @@ -1396,6 +1399,10 @@ 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,
> @@ -1469,6 +1476,56 @@ 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]);

What about PPHWSP_GUC_CONTEXT_USAGE_STAMP_HI? I see it defined but isn't
used so is the timestmap 32 bit just ABI reserved 64 bits for future
proofing or something?

Regards,

Tvrtko

> + 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)
> {
> @@ -2723,6 +2780,7 @@ 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);
>
> @@ -3344,6 +3402,7 @@ 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,
> @@ -3360,6 +3419,8 @@ 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,
>
> @@ -3593,6 +3654,7 @@ 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,
> @@ -3608,6 +3670,7 @@ 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,
>
> .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 b09d1d386574..8d81119fff14 100644
> --- a/drivers/gpu/drm/i915/i915_drm_client.c
> +++ b/drivers/gpu/drm/i915/i915_drm_client.c
> @@ -147,11 +147,7 @@ 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++)