On Wed, May 08, 2019 at 09:07:33PM +0200, Peter Zijlstra wrote:

On Tue, Apr 02, 2019 at 11:41:40AM +0100, Patrick Bellasi wrote:

quoted

+static inline struct uclamp_se
+uclamp_eff_get(struct task_struct *p, unsigned int clamp_id)
+{
+	struct uclamp_se uc_req = p->uclamp_req[clamp_id];
+	struct uclamp_se uc_max = uclamp_default[clamp_id];
+
+	/* System default restrictions always apply */
+	if (unlikely(uc_req.value > uc_max.value))
+		return uc_max;
+
+	return uc_req;
+}
+
+static inline unsigned int
+uclamp_eff_bucket_id(struct task_struct *p, unsigned int clamp_id)
+{
+	struct uclamp_se uc_eff;
+
+	/* Task currently refcounted: use back-annotated (effective) bucket */
+	if (p->uclamp[clamp_id].active)
+		return p->uclamp[clamp_id].bucket_id;
+
+	uc_eff = uclamp_eff_get(p, clamp_id);
+
+	return uc_eff.bucket_id;
+}
+
+unsigned int uclamp_eff_value(struct task_struct *p, unsigned int clamp_id)
+{
+	struct uclamp_se uc_eff;
+
+	/* Task currently refcounted: use back-annotated (effective) value */
+	if (p->uclamp[clamp_id].active)
+		return p->uclamp[clamp_id].value;
+
+	uc_eff = uclamp_eff_get(p, clamp_id);
+
+	return uc_eff.value;
+}

This is 'wrong' because:

  uclamp_eff_value(p,id) := uclamp_eff(p,id).value

Clearly I means to say the above does not hold with the given
implementation, while the naming would suggest it does.

Which seems to suggest the uclamp_eff_*() functions want another name.

Also, suppose the above would be true; does GCC really generate better
code for the LHS compared to the RHS?