On Thu, Apr 29, 2021 at 10:46:40AM +0100, Tvrtko Ursulin wrote:
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
>
> When a non-persistent context exits we currently mark it as banned in
> order to trigger fast termination of any outstanding GPU jobs it may have
> left running.
>
> In doing so we apply a very strict 1ms limit in which the left over job
> has to preempt before we issues an engine resets.
>
> Some workloads are not able to cleanly preempt in that time window and it
> can be argued that it would instead be better to give them a bit more
> grace since avoiding engine resets is generally preferrable.
Can you pls explain here why this is preferrable?
> To achieve this the patch splits handling of banned contexts from simply
> exited non-persistent ones and then applies different timeouts for both
> and also extends the criteria which determines if a request should be
> scheduled back in after preemption or not.
>
> 15ms preempt timeout grace is given to exited non-persistent contexts
> which have been empirically tested to satisfy customers requirements
> and still provides reasonably quick cleanup post exit.
Same here, a bit more detail on what exactly was the problem to be fixed
is needed.
-Daniel
>
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Zhen Han <zhen.han@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_context.c | 15 +++++++++------
> drivers/gpu/drm/i915/gt/intel_context.h | 17 +++++++++++++++++
> drivers/gpu/drm/i915/gt/intel_context_types.h | 1 +
> .../drm/i915/gt/intel_execlists_submission.c | 12 ++++++++++--
> drivers/gpu/drm/i915/i915_request.c | 2 +-
> 5 files changed, 38 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index fd8ee52e17a4..5a6eba1232cd 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -426,7 +426,8 @@ static struct intel_engine_cs *active_engine(struct intel_context *ce)
> return engine;
> }
>
> -static void kill_engines(struct i915_gem_engines *engines, bool ban)
> +static void
> +kill_engines(struct i915_gem_engines *engines, bool ban, bool persistent)
> {
> struct i915_gem_engines_iter it;
> struct intel_context *ce;
> @@ -443,6 +444,8 @@ static void kill_engines(struct i915_gem_engines *engines, bool ban)
>
> if (ban && intel_context_set_banned(ce))
> continue;
> + else if (!persistent && intel_context_set_non_persistent(ce))
> + continue;
>
> /*
> * Check the current active state of this context; if we
> @@ -454,7 +457,7 @@ static void kill_engines(struct i915_gem_engines *engines, bool ban)
> engine = active_engine(ce);
>
> /* First attempt to gracefully cancel the context */
> - if (engine && !__cancel_engine(engine) && ban)
> + if (engine && !__cancel_engine(engine) && (ban || !persistent))
> /*
> * If we are unable to send a preemptive pulse to bump
> * the context from the GPU, we have to resort to a full
> @@ -466,8 +469,6 @@ static void kill_engines(struct i915_gem_engines *engines, bool ban)
>
> static void kill_context(struct i915_gem_context *ctx)
> {
> - bool ban = (!i915_gem_context_is_persistent(ctx) ||
> - !ctx->i915->params.enable_hangcheck);
> struct i915_gem_engines *pos, *next;
>
> spin_lock_irq(&ctx->stale.lock);
> @@ -480,7 +481,8 @@ static void kill_context(struct i915_gem_context *ctx)
>
> spin_unlock_irq(&ctx->stale.lock);
>
> - kill_engines(pos, ban);
> + kill_engines(pos, !ctx->i915->params.enable_hangcheck,
> + i915_gem_context_is_persistent(ctx));
>
> spin_lock_irq(&ctx->stale.lock);
> GEM_BUG_ON(i915_sw_fence_signaled(&pos->fence));
> @@ -526,7 +528,8 @@ static void engines_idle_release(struct i915_gem_context *ctx,
>
> kill:
> if (list_empty(&engines->link)) /* raced, already closed */
> - kill_engines(engines, true);
> + kill_engines(engines, true,
> + i915_gem_context_is_persistent(ctx));
>
> i915_sw_fence_commit(&engines->fence);
> }
> diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
> index f83a73a2b39f..b0e812b8ce39 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context.h
> @@ -220,6 +220,23 @@ static inline bool intel_context_set_banned(struct intel_context *ce)
> return test_and_set_bit(CONTEXT_BANNED, &ce->flags);
> }
>
> +static inline bool intel_context_is_non_persistent(const struct intel_context *ce)
> +{
> + return test_bit(CONTEXT_NON_PERSISTENT, &ce->flags);
> +}
> +
> +static inline bool intel_context_set_non_persistent(struct intel_context *ce)
> +{
> + return test_and_set_bit(CONTEXT_NON_PERSISTENT, &ce->flags);
> +}
> +
> +static inline bool intel_context_is_schedulable(const struct intel_context *ce)
> +{
> + return !intel_context_is_banned(ce) &&
> + !(intel_context_is_closed(ce) &&
> + intel_context_is_non_persistent(ce));
> +}
> +
> static inline bool
> intel_context_force_single_submission(const struct intel_context *ce)
> {
> diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
> index ed8c447a7346..aa949c539e93 100644
> --- a/drivers/gpu/drm/i915/gt/intel_context_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
> @@ -95,6 +95,7 @@ struct intel_context {
> #define CONTEXT_BANNED 6
> #define CONTEXT_FORCE_SINGLE_SUBMISSION 7
> #define CONTEXT_NOPREEMPT 8
> +#define CONTEXT_NON_PERSISTENT 9 /* Only if also closed. */
>
> struct {
> u64 timeout_us;
> diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> index de124870af44..5ad7272fbbc4 100644
> --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
> @@ -478,7 +478,7 @@ __execlists_schedule_in(struct i915_request *rq)
> !intel_engine_has_heartbeat(engine)))
> intel_context_set_banned(ce);
>
> - if (unlikely(intel_context_is_banned(ce) || bad_request(rq)))
> + if (unlikely(!intel_context_is_schedulable(ce) || bad_request(rq)))
> reset_active(rq, engine);
>
> if (IS_ENABLED(CONFIG_DRM_I915_DEBUG_GEM))
> @@ -1204,12 +1204,20 @@ static void record_preemption(struct intel_engine_execlists *execlists)
> static unsigned long active_preempt_timeout(struct intel_engine_cs *engine,
> const struct i915_request *rq)
> {
> + struct intel_context *ce;
> +
> if (!rq)
> return 0;
>
> + ce = rq->context;
> +
> /* Force a fast reset for terminated contexts (ignoring sysfs!) */
> - if (unlikely(intel_context_is_banned(rq->context) || bad_request(rq)))
> + if (unlikely(intel_context_is_banned(ce) || bad_request(rq)))
> return 1;
> + /* Longer grace for closed non-persistent contexts to avoid resets. */
> + else if (unlikely(intel_context_is_closed(ce) &&
> + intel_context_is_non_persistent(ce)))
> + return 15;
>
> return READ_ONCE(engine->props.preempt_timeout_ms);
> }
> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> index bec9c3652188..bbac87535923 100644
> --- a/drivers/gpu/drm/i915/i915_request.c
> +++ b/drivers/gpu/drm/i915/i915_request.c
> @@ -660,7 +660,7 @@ bool __i915_request_submit(struct i915_request *request)
> goto active;
> }
>
> - if (unlikely(intel_context_is_banned(request->context)))
> + if (unlikely(!intel_context_is_schedulable(request->context)))
> i915_request_set_error_once(request, -EIO);
>
> if (unlikely(fatal_error(request->fence.error)))
> --
> 2.30.2
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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