[PATCH v3 5/6] drm/i915: Introduce 'priority offset' for GPU contexts (v2)

[Matt Roper <matthew.d.roper@intel.com>]

There are cases where a system integrator may wish to raise/lower the
priority of GPU workloads being submitted by specific OS process(es),
independently of how the software self-classifies its own priority.
Exposing "priority offset" as an i915-specific cgroup parameter will
enable such system-level configuration.

Normally GPU contexts start with a priority value of 0
(I915_CONTEXT_DEFAULT_PRIORITY) and then may be adjusted up/down from
there via other mechanisms.  We'd like to provide a system-level input
to the priority decision that will be taken into consideration, even
when userspace later attempts to set an absolute priority value via
I915_CONTEXT_PARAM_PRIORITY.  The priority offset introduced here
provides a base value that will always be added to (or subtracted from)
the software's self-assigned priority value.

This patch makes priority offset a cgroup-specific value; contexts will
be created with a priority offset based on the cgroup membership of the
process creating the context at the time the context is created.  Note
that priority offset is assigned at context creation time; migrating a
process to a different cgroup or changing the offset associated with a
cgroup will only affect new context creation and will not alter the
behavior of existing contexts previously created by the process.

v2:
 - Rebase onto new cgroup_priv API
 - Use current instead of drm_file->pid to determine which process to
   lookup priority for. (Chris)
 - Don't forget to subtract priority offset in context_getparam ioctl to
   make it match setparam behavior. (Chris)

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
---
 drivers/gpu/drm/i915/i915_cgroup.c      | 47 +++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_drv.h         | 15 ++++++-----
 drivers/gpu/drm/i915/i915_gem_context.c |  7 ++---
 drivers/gpu/drm/i915/i915_gem_context.h |  9 +++++++
 include/uapi/drm/i915_drm.h             |  1 +
 5 files changed, 69 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_cgroup.c b/drivers/gpu/drm/i915/i915_cgroup.c
index 4a46cb167f53..6a28b1a23971 100644
--- a/drivers/gpu/drm/i915/i915_cgroup.c
+++ b/drivers/gpu/drm/i915/i915_cgroup.c
@@ -13,6 +13,8 @@ struct i915_cgroup_data {
 	struct cgroup_priv base;
 
 	struct list_head node;
+
+	int priority_offset;
 };
 
 static inline struct i915_cgroup_data *
@@ -117,8 +119,10 @@ i915_cgroup_setparam_ioctl(struct drm_device *dev,
 			   void *data,
 			   struct drm_file *file)
 {
+	struct drm_i915_private *dev_priv = to_i915(dev);
 	struct drm_i915_cgroup_param *req = data;
 	struct cgroup *cgrp;
+	struct i915_cgroup_data *cgrpdata;
 	int ret;
 
 	/* We don't actually support any flags yet. */
@@ -154,7 +158,18 @@ i915_cgroup_setparam_ioctl(struct drm_device *dev,
 	if (ret)
 		goto out;
 
+	cgrpdata = get_or_create_cgroup_data(dev_priv, cgrp);
+	if (IS_ERR(cgrpdata)) {
+		ret = PTR_ERR(cgrpdata);
+		goto out;
+	}
+
 	switch (req->param) {
+	case I915_CGROUP_PARAM_PRIORITY_OFFSET:
+		DRM_DEBUG_DRIVER("Setting cgroup priority offset to %lld\n",
+				 req->value);
+		cgrpdata->priority_offset = req->value;
+		break;
 	default:
 		DRM_DEBUG_DRIVER("Invalid cgroup parameter %lld\n", req->param);
 		ret = -EINVAL;
@@ -165,3 +180,35 @@ i915_cgroup_setparam_ioctl(struct drm_device *dev,
 
 	return ret;
 }
+
+/**
+ * i915_cgroup_get_prio_offset() - get prio offset for current proc's cgroup
+ * @dev_priv: drm device
+ * @file_priv: file handle for calling process
+ *
+ * RETURNS:
+ * Priority offset associated with the calling process' cgroup in the default
+ * (v2) hierarchy, otherwise 0 if no explicit priority has been assigned.
+ */
+int
+i915_cgroup_get_current_prio_offset(struct drm_i915_private *dev_priv)
+{
+       struct cgroup *cgrp;
+       struct cgroup_priv *cgrpdata;
+       int offset = 0;
+
+       cgrp = task_get_dfl_cgroup(current);
+       if (WARN_ON(!cgrp))
+               return 0;
+
+       mutex_lock(&cgrp->privdata_mutex);
+
+       cgrpdata = cgroup_priv_lookup(cgrp, dev_priv);
+       if (cgrpdata)
+	       offset = cgrp_to_i915(cgrpdata)->priority_offset;
+
+       mutex_unlock(&cgrp->privdata_mutex);
+       cgroup_put(cgrp);
+
+       return offset;
+}
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 7c38142ee009..51b80926d20c 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2947,18 +2947,19 @@ void i915_cgroup_init(struct drm_i915_private *dev_priv);
 int i915_cgroup_setparam_ioctl(struct drm_device *dev, void *data,
 			       struct drm_file *file);
 void i915_cgroup_shutdown(struct drm_i915_private *dev_priv);
+int i915_cgroup_get_current_prio_offset(struct drm_i915_private *dev_priv);
 #else
-static inline int
-i915_cgroup_init(struct drm_i915_private *dev_priv)
+static inline void i915_cgroup_init(struct drm_i915_private *dev_priv) {}
+static inline void i915_cgroup_shutdown(struct drm_i915_private *dev_priv) {}
+static inline int i915_cgroup_setparam_ioctl(struct drm_device *dev, void *data,
+					     struct drm_file *file)
 {
-	return 0;
+	return -EINVAL;
 }
-static inline void i915_cgroup_shutdown(struct drm_i915_private *dev_priv) {}
 static inline int
-i915_cgroup_setparam_ioctl(struct drm_device *dev, void *data,
-			   struct drm_file *file)
+i915_cgroup_get_current_prio_offset(struct drm_i915_private *dev_priv)
 {
-	return -EINVAL;
+	return 0;
 }
 #endif
 
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index a73340ae9419..b29fbe0c776f 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -274,7 +274,8 @@ __create_hw_context(struct drm_i915_private *dev_priv,
 	kref_init(&ctx->ref);
 	list_add_tail(&ctx->link, &dev_priv->contexts.list);
 	ctx->i915 = dev_priv;
-	ctx->priority = I915_PRIORITY_NORMAL;
+	ctx->priority_offset = i915_cgroup_get_current_prio_offset(dev_priv);
+	ctx->priority = I915_PRIORITY_NORMAL + ctx->priority_offset;
 
 	INIT_RADIX_TREE(&ctx->handles_vma, GFP_KERNEL);
 	INIT_LIST_HEAD(&ctx->handles_list);
@@ -739,7 +740,7 @@ int i915_gem_context_getparam_ioctl(struct drm_device *dev, void *data,
 		args->value = i915_gem_context_is_bannable(ctx);
 		break;
 	case I915_CONTEXT_PARAM_PRIORITY:
-		args->value = ctx->priority;
+		args->value = ctx->priority - ctx->priority_offset;
 		break;
 	default:
 		ret = -EINVAL;
@@ -812,7 +813,7 @@ int i915_gem_context_setparam_ioctl(struct drm_device *dev, void *data,
 				 !capable(CAP_SYS_NICE))
 				ret = -EPERM;
 			else
-				ctx->priority = priority;
+				ctx->priority = priority + ctx->priority_offset;
 		}
 		break;
 
diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index 7854262ddfd9..c3b4fb54fbb6 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -150,6 +150,15 @@ struct i915_gem_context {
 	 */
 	int priority;
 
+	/**
+	 * @priority_offset: priority offset
+	 *
+	 * A value, configured via cgroup, that sets the starting priority
+	 * of the context.  Any priority set explicitly via context parameter
+	 * will be added to the priority offset.
+	 */
+	int priority_offset;
+
 	/** ggtt_offset_bias: placement restriction for context objects */
 	u32 ggtt_offset_bias;
 
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index b6651b263838..5b67aaf8a1c0 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1624,6 +1624,7 @@ struct drm_i915_cgroup_param {
 	__s32 cgroup_fd;
 	__u32 flags;
 	__u64 param;
+#define I915_CGROUP_PARAM_PRIORITY_OFFSET	0x1
 	__s64 value;
 };
 
-- 
2.14.3

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel