From db3d8338bacbfc734d246eaccfbe5b19ad81d7d4 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Fri, 28 Feb 2020 13:17:15 +0000 Subject: [PATCH] drm/i915/gt: Expose preempt reset timeout via sysfs 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 Reviewed-by: Steve Carbonari Tested-by: Steve Carbonari Link: https://patchwork.freedesktop.org/patch/msgid/20200228131716.3243616-6-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/Kconfig.profile | 3 ++ drivers/gpu/drm/i915/gt/sysfs_engines.c | 48 +++++++++++++++++++++++++ 2 files changed, 51 insertions(+) diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile index 5f4ec3aec1d28..1f4e98a8532f7 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/sysfs_engines.c b/drivers/gpu/drm/i915/gt/sysfs_engines.c index b7b62a439ddd8..0c109adb18b82 100644 --- a/drivers/gpu/drm/i915/gt/sysfs_engines.c +++ b/drivers/gpu/drm/i915/gt/sysfs_engines.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); @@ -338,6 +382,10 @@ 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);