On Thu, Dec 12, 2019 at 02:04:57PM +0000, Chris Wilson wrote:
> After initialising a preemption request, we give the current resident a
> small amount of time to vacate the GPU. The preemption request is for a
> higher priority context and should be immediate to maintain high
> quality of service (and avoid priority inversion). However, the
> preemption granularity of the GPU can be quite coarse and so we need a
> compromise.
>
> The preempt timeout can be adjusted per-engine using,
>
> /sys/class/drm/card?/engine/*/preempt_timeout_ms
>
> and can be disabled by setting it to 0.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Code looks good.
Tested with other sysfs related patches in the series.
The preempt_timeout_ms file exists and can be modified.
Tested when there is no reset engine and the sysfs file
is not created.
Reviewed-by: Steve Carbonari <steven.carbonari@xxxxxxxxx>
Tested-by: Steve Carbonari <steven.carbonari@xxxxxxxxx
> ---
> drivers/gpu/drm/i915/Kconfig.profile | 3 ++
> drivers/gpu/drm/i915/gt/intel_engine_sysfs.c | 48 ++++++++++++++++++++
> drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +-
> 3 files changed, 52 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile
> index 5f4ec3aec1d2..1f4e98a8532f 100644
> --- a/drivers/gpu/drm/i915/Kconfig.profile
> +++ b/drivers/gpu/drm/i915/Kconfig.profile
> @@ -33,6 +33,9 @@ config DRM_I915_PREEMPT_TIMEOUT
> expires, the HW will be reset to allow the more important context
> to execute.
>
> + This is adjustable via
> + /sys/class/drm/card?/engine/*/preempt_timeout_ms
> +
> May be 0 to disable the timeout.
>
> config DRM_I915_MAX_REQUEST_BUSYWAIT
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_sysfs.c b/drivers/gpu/drm/i915/gt/intel_engine_sysfs.c
> index 2b65fed76435..d299c66cf7ec 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_sysfs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_sysfs.c
> @@ -271,6 +271,50 @@ stop_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> static struct kobj_attribute stop_timeout_attr =
> __ATTR(stop_timeout_ms, 0644, stop_show, stop_store);
>
> +static ssize_t
> +preempt_timeout_store(struct kobject *kobj, struct kobj_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct intel_engine_cs *engine = kobj_to_engine(kobj);
> + unsigned long long timeout;
> + int err;
> +
> + /*
> + * After initialising a preemption request, we give the current
> + * resident a small amount of time to vacate the GPU. The preemption
> + * request is for a higher priority context and should be immediate to
> + * maintain high quality of service (and avoid priority inversion).
> + * However, the preemption granularity of the GPU can be quite coarse
> + * and so we need a compromise.
> + */
> +
> + err = kstrtoull(buf, 0, &timeout);
> + if (err)
> + return err;
> +
> + if (timeout > jiffies_to_msecs(MAX_SCHEDULE_TIMEOUT))
> + return -EINVAL;
> +
> + WRITE_ONCE(engine->props.preempt_timeout_ms, timeout);
> +
> + if (READ_ONCE(engine->execlists.pending[0]))
> + set_timer_ms(&engine->execlists.preempt, timeout);
> +
> + return count;
> +}
> +
> +static ssize_t
> +preempt_timeout_show(struct kobject *kobj, struct kobj_attribute *attr,
> + char *buf)
> +{
> + struct intel_engine_cs *engine = kobj_to_engine(kobj);
> +
> + return sprintf(buf, "%lu\n", engine->props.preempt_timeout_ms);
> +}
> +
> +static struct kobj_attribute preempt_timeout_attr =
> +__ATTR(preempt_timeout_ms, 0644, preempt_timeout_show, preempt_timeout_store);
> +
> static void kobj_engine_release(struct kobject *kobj)
> {
> kfree(kobj);
> @@ -341,6 +385,10 @@ void intel_engines_add_sysfs(struct drm_i915_private *i915)
> sysfs_create_file(kobj, ×lice_duration_attr.attr))
> goto err_engine;
>
> + if (intel_engine_has_preempt_reset(engine) &&
> + sysfs_create_file(kobj, &preempt_timeout_attr.attr))
> + goto err_engine;
> +
> if (0) {
> err_object:
> kobject_put(kobj);
> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> index 024a639da787..9a9b23e3d0a3 100644
> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> @@ -2252,7 +2252,7 @@ static noinline void preempt_reset(struct intel_engine_cs *engine)
> const unsigned int bit = I915_RESET_ENGINE + engine->id;
> unsigned long *lock = &engine->gt->reset.flags;
>
> - if (i915_modparams.reset < 3)
> + if (!intel_has_reset_engine(engine->gt))
> return;
>
> if (test_and_set_bit(bit, lock))
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