[RFC 16/17] drm/i915: Expose per-engine client busyness

[Tvrtko Ursulin <tursulin@ursulin.net>]

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Expose per-client and per-engine busyness under the previously added sysfs
client root.

The new file is named 'busy' and contains a list of, one line for each
engine, monotonically increasing nano-second resolution times each
client's jobs were executing on the GPU.

$ cat /sys/class/drm/card0/clients/5/busy
32516602
0
0
0

This data can serve as an interface to implement a top like utility for
GPU jobs. For instance I have prototyped a tool in IGT which produces
periodic output like:

neverball[  6011]:  rcs0:  41.01%  bcs0:   0.00%  vcs0:   0.00%  vecs0:   0.00%
     Xorg[  5664]:  rcs0:  31.16%  bcs0:   0.00%  vcs0:   0.00%  vecs0:   0.00%
    xfwm4[  5727]:  rcs0:   0.00%  bcs0:   0.00%  vcs0:   0.00%  vecs0:   0.00%

This tools can also be extended to use the i915 PMU and show overall engine
busyness, and engine loads using the queue depth metric.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h |  1 +
 drivers/gpu/drm/i915/i915_gem.c | 65 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 66 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index cc98c643f42b..d74111b397b4 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -631,6 +631,7 @@ struct drm_i915_file_private {
 	struct {
 		struct device_attribute pid;
 		struct device_attribute name;
+		struct device_attribute busy;
 	} attr;
 };
 
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e8a30c1ceb4f..7a0b96c04666 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -5251,6 +5251,56 @@ show_client_pid(struct device *kdev, struct device_attribute *attr, char *buf)
 	return snprintf(buf, PAGE_SIZE, "%u", file_priv->client_pid);
 }
 
+struct busy_ctx {
+	u64 total[I915_NUM_ENGINES];
+};
+
+static int busy_add(int _id, void *p, void *data)
+{
+	struct i915_gem_context *ctx = p;
+	struct busy_ctx *bc = data;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+
+	for_each_engine(engine, ctx->i915, id)
+		bc->total[id] += ctx->engine[id].stats.total;
+
+	return 0;
+}
+
+static ssize_t
+show_client_busy(struct device *kdev, struct device_attribute *attr, char *buf)
+{
+	struct drm_i915_file_private *file_priv =
+		container_of(attr, struct drm_i915_file_private, attr.busy);
+	struct drm_i915_private *i915 = file_priv->dev_priv;
+	unsigned int len = PAGE_SIZE;
+	struct busy_ctx bc = { };
+	ssize_t res = 0;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	ssize_t ret;
+
+	ret = i915_mutex_lock_interruptible(&i915->drm);
+	if (ret)
+		return ret;
+
+	idr_for_each(&file_priv->context_idr, busy_add, &bc);
+
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	for_each_engine(engine, i915, id) {
+		ret = snprintf(buf, len, "%llu\n", bc.total[id]);
+		if (ret <= 0)
+			break;
+		res += ret;
+		len -= ret;
+		buf += ret;
+	}
+
+	return res;
+}
+
 int
 i915_gem_add_client(struct drm_i915_private *i915,
 		struct drm_i915_file_private *file_priv,
@@ -5291,10 +5341,23 @@ i915_gem_add_client(struct drm_i915_private *i915,
 	if (ret)
 		goto err_attr_pid;
 
+	attr = &file_priv->attr.busy;
+	attr->attr.name = "busy";
+	attr->attr.mode = 0444;
+	attr->show = show_client_busy;
+
+	ret = sysfs_create_file(file_priv->client_root,
+				(struct attribute *)attr);
+	if (ret)
+		goto err_attr_busy;
+
 	file_priv->client_pid = pid_nr(get_task_pid(task, PIDTYPE_PID));
 
 	return 0;
 
+err_attr_busy:
+	sysfs_remove_file(file_priv->client_root,
+			  (struct attribute *)&file_priv->attr.pid);
 err_attr_pid:
 	sysfs_remove_file(file_priv->client_root,
 			  (struct attribute *)&file_priv->attr.name);
@@ -5309,6 +5372,8 @@ i915_gem_add_client(struct drm_i915_private *i915,
 void i915_gem_remove_client(struct drm_i915_file_private *file_priv)
 {
 	sysfs_remove_file(file_priv->client_root,
+			  (struct attribute *)&file_priv->attr.busy);
+	sysfs_remove_file(file_priv->client_root,
 			  (struct attribute *)&file_priv->attr.pid);
 	sysfs_remove_file(file_priv->client_root,
 			  (struct attribute *)&file_priv->attr.name);
-- 
2.9.5

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