Now that we have the information about which cores are fully idle, use
it for tickling pcpus.
This way, if there are cores that are fully idle, we tickle a pcpu from
one of them. This improve the SMT-awareness of the scheduler,
guaranteeing a better distribution of load, right from vcpu wakeup.
Signed-off-by: Dario Faggioli <dfaggi...@suse.com>
---
Cc: George Dunlap <george.dun...@eu.citrix.com>
---
xen/common/sched_credit.c | 51 +++++++++++++++++++++++++++------------------
1 file changed, 31 insertions(+), 20 deletions(-)
diff --git a/xen/common/sched_credit.c b/xen/common/sched_credit.c
index c7ee85d56a..af3b81d377 100644
--- a/xen/common/sched_credit.c
+++ b/xen/common/sched_credit.c
@@ -424,6 +424,15 @@ static inline void __runq_tickle(struct csched_vcpu *new)
cpumask_scratch_cpu(cpu));
cpumask_and(cpumask_scratch_cpu(cpu),
cpumask_scratch_cpu(cpu), &idle_mask);
+
+ /* Let's check fully idle cores first. */
+ if ( cpumask_intersects(cpumask_scratch_cpu(cpu), prv->smt_idle) )
+ {
+ cpumask_and(&mask, cpumask_scratch_cpu(cpu), prv->smt_idle);
+ break;
+ }
+
+ /* Now, let's check all idlers. */
new_idlers_empty = cpumask_empty(cpumask_scratch_cpu(cpu));
/*
@@ -441,11 +450,6 @@ static inline void __runq_tickle(struct csched_vcpu *new)
* We have to do it indirectly, via _VPF_migrating (instead
* of just tickling any idler suitable for cur) because cur
* is running.
- *
- * If there are suitable idlers for new, no matter priorities,
- * leave cur alone (as it is running and is, likely, cache-hot)
- * and wake some of them (which is waking up and so is, likely,
- * cache cold anyway).
*/
if ( new_idlers_empty && new->pri > cur->pri )
{
@@ -460,23 +464,19 @@ static inline void __runq_tickle(struct csched_vcpu *new)
/* Tickle cpu anyway, to let new preempt cur. */
SCHED_STAT_CRANK(tickled_busy_cpu);
__cpumask_set_cpu(cpu, &mask);
+ goto tickle;
}
- else if ( !new_idlers_empty )
+
+ /*
+ * If there are suitable idlers for new, no matter priorities,
+ * leave cur alone (as it is running and is, likely, cache-hot)
+ * and wake some of them (which is waking up and so is, likely,
+ * cache cold anyway).
+ */
+ if ( !new_idlers_empty )
{
- /* Which of the idlers suitable for new shall we wake up? */
SCHED_STAT_CRANK(tickled_idle_cpu);
- if ( opt_tickle_one_idle )
- {
- if ( cpumask_test_cpu(cpu, cpumask_scratch_cpu(cpu)) )
- this_cpu(last_tickle_cpu) = cpu;
- else
- this_cpu(last_tickle_cpu) =
- cpumask_cycle(this_cpu(last_tickle_cpu),
- cpumask_scratch_cpu(cpu));
- __cpumask_set_cpu(this_cpu(last_tickle_cpu), &mask);
- }
- else
- cpumask_or(&mask, &mask, cpumask_scratch_cpu(cpu));
+ cpumask_or(&mask, &mask, cpumask_scratch_cpu(cpu));
}
/* Did we find anyone? */
@@ -485,9 +485,20 @@ static inline void __runq_tickle(struct csched_vcpu *new)
}
}
- tickle:
if ( !cpumask_empty(&mask) )
{
+ /* Which of the idlers suitable for new shall we wake up? */
+ if ( opt_tickle_one_idle )
+ {
+ if ( cpumask_test_cpu(cpu, &mask) )
+ this_cpu(last_tickle_cpu) = cpu;
+ else
+ this_cpu(last_tickle_cpu) =
+ cpumask_cycle(this_cpu(last_tickle_cpu), &mask);
+ cpumask_copy(&mask, cpumask_of(this_cpu(last_tickle_cpu)));
+ }
+
+ tickle:
if ( unlikely(tb_init_done) )
{
/* Avoid TRACE_*: saves checking !tb_init_done each step */
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