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sched/numa: Implement NUMA node level wake_affine() 

Since select_idle_sibling() can place a task anywhere on a socket,
comparing loads between individual CPU cores makes no real sense
for deciding whether to do an affine wakeup across sockets, either.

Instead, compare the load between the sockets in a similar way the
load balancer and the numa balancing code do.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: jhladky@redhat.com
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20170623165530.22514-4-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Rik van Riel 2017-06-23 12:55:29 -04:00 committed by Ingo Molnar
parent 7d894e6e34
commit 3fed382b46
1 changed files with 71 additions and 59 deletions
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130
kernel/sched/fair.c
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@ -2586,6 +2586,60 @@ void task_tick_numa(struct rq *rq, struct task_struct *curr)
}
}
}
/*
* Can a task be moved from prev_cpu to this_cpu without causing a load
* imbalance that would trigger the load balancer?
*/
static inline bool numa_wake_affine(struct sched_domain *sd,
struct task_struct *p, int this_cpu,
int prev_cpu, int sync)
{
struct numa_stats prev_load, this_load;
s64 this_eff_load, prev_eff_load;
update_numa_stats(&prev_load, cpu_to_node(prev_cpu));
update_numa_stats(&this_load, cpu_to_node(this_cpu));
/*
* If sync wakeup then subtract the (maximum possible)
* effect of the currently running task from the load
* of the current CPU:
*/
if (sync) {
unsigned long current_load = task_h_load(current);
if (this_load.load > current_load)
this_load.load -= current_load;
else
this_load.load = 0;
}
/*
* In low-load situations, where this_cpu's node is idle due to the
* sync cause above having dropped this_load.load to 0, move the task.
* Moving to an idle socket will not create a bad imbalance.
*
* Otherwise check if the nodes are near enough in load to allow this
* task to be woken on this_cpu's node.
*/
if (this_load.load > 0) {
unsigned long task_load = task_h_load(p);
this_eff_load = 100;
this_eff_load *= prev_load.compute_capacity;
prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
prev_eff_load *= this_load.compute_capacity;
this_eff_load *= this_load.load + task_load;
prev_eff_load *= prev_load.load - task_load;
return this_eff_load <= prev_eff_load;
}
return true;
}
#else
static void task_tick_numa(struct rq *rq, struct task_struct *curr)
{
@ -2598,6 +2652,13 @@ static inline void account_numa_enqueue(struct rq *rq, struct task_struct *p)
static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
{
}
static inline bool numa_wake_affine(struct sched_domain *sd,
struct task_struct *p, int this_cpu,
int prev_cpu, int sync)
{
return true;
}
#endif /* CONFIG_NUMA_BALANCING */
static void
@ -5407,74 +5468,25 @@ static int wake_wide(struct task_struct *p)
static int wake_affine(struct sched_domain *sd, struct task_struct *p,
int prev_cpu, int sync)
{
s64 this_load, load;
s64 this_eff_load, prev_eff_load;
int idx, this_cpu;
struct task_group *tg;
unsigned long weight;
int balanced;
idx = sd->wake_idx;
this_cpu = smp_processor_id();
load = source_load(prev_cpu, idx);
this_load = target_load(this_cpu, idx);
int this_cpu = smp_processor_id();
bool affine = false;
/*
* Common case: CPUs are in the same socket, and select_idle_sibling()
* will do its thing regardless of what we return:
*/
if (cpus_share_cache(prev_cpu, this_cpu))
return true;
/*
* If sync wakeup then subtract the (maximum possible)
* effect of the currently running task from the load
* of the current CPU:
*/
if (sync) {
tg = task_group(current);
weight = current->se.avg.load_avg;
this_load += effective_load(tg, this_cpu, -weight, -weight);
load += effective_load(tg, prev_cpu, 0, -weight);
}
tg = task_group(p);
weight = p->se.avg.load_avg;
/*
* In low-load situations, where prev_cpu is idle and this_cpu is idle
* due to the sync cause above having dropped this_load to 0, we'll
* always have an imbalance, but there's really nothing you can do
* about that, so that's good too.
*
* Otherwise check if either cpus are near enough in load to allow this
* task to be woken on this_cpu.
*/
this_eff_load = 100;
this_eff_load *= capacity_of(prev_cpu);
prev_eff_load = 100 + (sd->imbalance_pct - 100) / 2;
prev_eff_load *= capacity_of(this_cpu);
if (this_load > 0) {
this_eff_load *= this_load +
effective_load(tg, this_cpu, weight, weight);
prev_eff_load *= load + effective_load(tg, prev_cpu, 0, weight);
}
balanced = this_eff_load <= prev_eff_load;
affine = true;
else
affine = numa_wake_affine(sd, p, this_cpu, prev_cpu, sync);
schedstat_inc(p->se.statistics.nr_wakeups_affine_attempts);
if (affine) {
schedstat_inc(sd->ttwu_move_affine);
schedstat_inc(p->se.statistics.nr_wakeups_affine);
}
if (!balanced)
return 0;
schedstat_inc(sd->ttwu_move_affine);
schedstat_inc(p->se.statistics.nr_wakeups_affine);
return 1;
return affine;
}
static inline int task_util(struct task_struct *p);