* util_cfs + util_dl as requested freq. However, cpufreq is not yet
* ready for such an interface. So, we only do the latter for now.
*/
- return min(util, sg_cpu->max);
+ return min(sg_cpu->max, (sg_cpu->util_dl + sg_cpu->util_cfs));
}
- static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time, unsigned int flags)
+ /**
+ * sugov_iowait_reset() - Reset the IO boost status of a CPU.
+ * @sg_cpu: the sugov data for the CPU to boost
+ * @time: the update time from the caller
+ * @set_iowait_boost: true if an IO boost has been requested
+ *
+ * The IO wait boost of a task is disabled after a tick since the last update
+ * of a CPU. If a new IO wait boost is requested after more then a tick, then
+ * we enable the boost starting from the minimum frequency, which improves
+ * energy efficiency by ignoring sporadic wakeups from IO.
+ */
+ static bool sugov_iowait_reset(struct sugov_cpu *sg_cpu, u64 time,
+ bool set_iowait_boost)
{
- if (flags & SCHED_CPUFREQ_IOWAIT) {
- if (sg_cpu->iowait_boost_pending)
- return;
+ s64 delta_ns = time - sg_cpu->last_update;
- sg_cpu->iowait_boost_pending = true;
+ /* Reset boost only if a tick has elapsed since last request */
+ if (delta_ns <= TICK_NSEC)
+ return false;
- if (sg_cpu->iowait_boost) {
- sg_cpu->iowait_boost <<= 1;
- if (sg_cpu->iowait_boost > sg_cpu->iowait_boost_max)
- sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
- } else {
- sg_cpu->iowait_boost = sg_cpu->sg_policy->policy->min;
- }
- } else if (sg_cpu->iowait_boost) {
- s64 delta_ns = time - sg_cpu->last_update;
+ sg_cpu->iowait_boost = set_iowait_boost
+ ? sg_cpu->sg_policy->policy->min : 0;
+ sg_cpu->iowait_boost_pending = set_iowait_boost;
- /* Clear iowait_boost if the CPU apprears to have been idle. */
- if (delta_ns > TICK_NSEC) {
- sg_cpu->iowait_boost = 0;
- sg_cpu->iowait_boost_pending = false;
- }
+ return true;
+ }
+
+ /**
+ * sugov_iowait_boost() - Updates the IO boost status of a CPU.
+ * @sg_cpu: the sugov data for the CPU to boost
+ * @time: the update time from the caller
+ * @flags: SCHED_CPUFREQ_IOWAIT if the task is waking up after an IO wait
+ *
+ * Each time a task wakes up after an IO operation, the CPU utilization can be
+ * boosted to a certain utilization which doubles at each "frequent and
+ * successive" wakeup from IO, ranging from the utilization of the minimum
+ * OPP to the utilization of the maximum OPP.
+ * To keep doubling, an IO boost has to be requested at least once per tick,
+ * otherwise we restart from the utilization of the minimum OPP.
+ */
+ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
+ unsigned int flags)
+ {
+ bool set_iowait_boost = flags & SCHED_CPUFREQ_IOWAIT;
+
+ /* Reset boost if the CPU appears to have been idle enough */
+ if (sg_cpu->iowait_boost &&
+ sugov_iowait_reset(sg_cpu, time, set_iowait_boost))
+ return;
+
+ /* Boost only tasks waking up after IO */
+ if (!set_iowait_boost)
+ return;
+
+ /* Ensure boost doubles only one time at each request */
+ if (sg_cpu->iowait_boost_pending)
+ return;
+ sg_cpu->iowait_boost_pending = true;
+
+ /* Double the boost at each request */
+ if (sg_cpu->iowait_boost) {
+ sg_cpu->iowait_boost <<= 1;
+ if (sg_cpu->iowait_boost > sg_cpu->iowait_boost_max)
+ sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
+ return;
}
+
+ /* First wakeup after IO: start with minimum boost */
+ sg_cpu->iowait_boost = sg_cpu->sg_policy->policy->min;
}
- static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,
- unsigned long *max)
+ /**
+ * sugov_iowait_apply() - Apply the IO boost to a CPU.
+ * @sg_cpu: the sugov data for the cpu to boost
+ * @time: the update time from the caller
+ * @util: the utilization to (eventually) boost
+ * @max: the maximum value the utilization can be boosted to
+ *
+ * A CPU running a task which woken up after an IO operation can have its
+ * utilization boosted to speed up the completion of those IO operations.
+ * The IO boost value is increased each time a task wakes up from IO, in
+ * sugov_iowait_apply(), and it's instead decreased by this function,
+ * each time an increase has not been requested (!iowait_boost_pending).
+ *
+ * A CPU which also appears to have been idle for at least one tick has also
+ * its IO boost utilization reset.
+ *
+ * This mechanism is designed to boost high frequently IO waiting tasks, while
+ * being more conservative on tasks which does sporadic IO operations.
+ */
+ static void sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
+ unsigned long *util, unsigned long *max)
{
unsigned int boost_util, boost_max;
projects / linux-2.6-microblaze.git / commitdiff