Re: [Intel-gfx] [RFC 6/8] drm/i915: Expose per-engine client busyness

Chris Wilson
2020-01-10T14:13:19Z

Quoting Tvrtko Ursulin (2020-01-10 14:09:09)
>
> On 10/01/2020 13:58, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2020-01-10 13:30:47)
> >> +static ssize_t
> >> +show_client_busy(struct device *kdev, struct device_attribute *attr, char *buf)
> >> +{
> >> + struct i915_engine_busy_attribute *i915_attr =
> >> + container_of(attr, typeof(*i915_attr), attr);
> >> + struct list_head *list = &i915_attr->client->ctx_list;
> >> + unsigned int engine_class = i915_attr->engine_class;
> >> + struct i915_gem_context *ctx;
> >> + u64 total = 0;
> >> +
> >> + if (i915_attr->no_busy_stats)
> >> + return -ENODEV;
> >> +
> >> + rcu_read_lock();
> >> + list_for_each_entry_rcu(ctx, list, client_link)
> >> + total += sw_busy_add(ctx, engine_class);
> >> + rcu_read_unlock();
> >> +
> >> + return snprintf(buf, PAGE_SIZE, "%llu\n", total);
> >> +}
> >> +
> >> +static const char *uabi_class_names[] = {
> >> + [I915_ENGINE_CLASS_RENDER] = "0",
> >> + [I915_ENGINE_CLASS_COPY] = "1",
> >> + [I915_ENGINE_CLASS_VIDEO] = "2",
> >> + [I915_ENGINE_CLASS_VIDEO_ENHANCE] = "3",
> >> +};
> >
> > Hmm. /sys/class/drm/card0/clients/0/busy/0
> >
> > Ok. I was worried this was 0/0 and so very bland and liable to clash
> > later.
> >
> >> +
> >> int
> >> __i915_drm_client_register(struct i915_drm_client *client,
> >> struct task_struct *task)
> >> {
> >> struct i915_drm_clients *clients = client->clients;
> >> + struct drm_i915_private *i915 =
> >> + container_of(clients, typeof(*i915), clients);
> >> + struct intel_engine_cs *engine;
> >> struct device_attribute *attr;
> >> - int ret = -ENOMEM;
> >> + int i, ret = -ENOMEM;
> >> char idstr[32];
> >>
> >> if (!clients->root)
> >> @@ -77,10 +130,71 @@ __i915_drm_client_register(struct i915_drm_client *client,
> >> if (ret)
> >> goto err_attr;
> >>
> >> + if (HAS_LOGICAL_RING_CONTEXTS(i915)) {
> >> + client->busy_root =
> >> + kobject_create_and_add("busy", client->root);
> >> + if (!client->busy_root)
> >> + goto err_attr;
> >> +
> >> + for (i = 0; i < ARRAY_SIZE(uabi_class_names); i++) {
> >> + struct i915_engine_busy_attribute *i915_attr =
> >> + &client->attr.busy[i];
> >
> >
> > if (!intel_engine_lookup_user(i915, i, 0))
> > continue;
> >
> > i.e. skip if we don't have any engines of that class in the system.
>
> Yes, thanks.
>
> >> +
> >> + i915_attr->client = client;
> >> + i915_attr->engine_class = i;
> >> +
> >> + attr = &i915_attr->attr;
> >> +
> >> + sysfs_attr_init(&attr->attr);
> >> +
> >> + attr->attr.name = uabi_class_names[i];
> >> + attr->attr.mode = 0444;
> >> + attr->show = show_client_busy;
> >> +
> >> + ret = sysfs_create_file(client->busy_root,
> >> + (struct attribute *)attr);
> >> + if (ret)
> >> + goto err_busy;
> >> + }
> >> +
> >> + /* Enable busy stats on all engines. */
> >> + i = 0;
> >> + for_each_uabi_engine(engine, i915) {
> >> + ret = intel_enable_engine_stats(engine);
> >
> > Hmm. We gave it a global bit in
> >
> > i915->caps.scheduler & I915_SCHEDULER_CAP_ENABLED.
> >
> > That'll avoid having to do the individual checking and rollback.
>
> I could add a top level check as a short circuit, but I prefer to check
> return code from intel_enable_engine_stats since it returns one.

My suggestion was to remove the return code and make it bug out, as we
[can] check before use in i915_pmu.c as well.

> Also if new GuC will have I915_SCHEDULER_CAP_ENABLED it will still fail
> to enable engine stats and then fallback to pphwsp has to happen.

Brainfart, CAP_SUPPORTS_STATS.
-Chris