From: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
Testing indicates that it is possible to improve performace
significantly without increasing energy consumption too much by
teaching cpufreq governors to bump up the CPU performance level if
the in_iowait flag is set for the task in enqueue_task_fair().
For this purpose, define a new cpufreq_update_util() flag
SCHED_CPUFREQ_IOWAIT and modify enqueue_task_fair() to pass that
flag to cpufreq_update_util() in the in_iowait case. That generally
requires cpufreq_update_util() to be called directly from there,
because update_load_avg() may not be invoked in that case.
Signed-off-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
---
include/linux/sched.h | 1 +
kernel/sched/fair.c | 8 ++++++++
2 files changed, 9 insertions(+)
Index: linux-pm/kernel/sched/fair.c
===================================================================
--- linux-pm.orig/kernel/sched/fair.c
+++ linux-pm/kernel/sched/fair.c
@@ -4500,6 +4500,14 @@ enqueue_task_fair(struct rq *rq, struct
struct cfs_rq *cfs_rq;
struct sched_entity *se = &p->se;
+ /*
+ * If in_iowait is set, the code below may not trigger any cpufreq
+ * utilization updates, so do it here explicitly with the IOWAIT flag
+ * passed.
+ */
+ if (p->in_iowait)
+ cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_IOWAIT);
+
for_each_sched_entity(se) {
if (se->on_rq)
break;
Index: linux-pm/include/linux/sched.h
===================================================================
--- linux-pm.orig/include/linux/sched.h
+++ linux-pm/include/linux/sched.h
@@ -3471,6 +3471,7 @@ static inline unsigned long rlimit_max(u
#define SCHED_CPUFREQ_RT (1U << 0)
#define SCHED_CPUFREQ_DL (1U << 1)
+#define SCHED_CPUFREQ_IOWAIT (1U << 2)
#define SCHED_CPUFREQ_RT_DL (SCHED_CPUFREQ_RT | SCHED_CPUFREQ_DL)
