For CFS load balancer, - mask out paravirt CPUs from list of cpus to balance. - This helps to restrict/expand the workload depending on the mask.
At wakeup, - If prev_cpu is paravirt, see if recent_used_cpu can be chosen. If not choose current cpu. - For EAS system, put a warning if wake up happens on paravirt CPU. At this point, not expecting any EAS system will have a overcommit of CPUs. Signed-off-by: Shrikanth Hegde <[email protected]> --- kernel/sched/fair.c | 36 +++++++++++++++++++++++++++++++++++- 1 file changed, 35 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 015e00b370c9..760813802cb9 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7358,6 +7358,9 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, { int target = nr_cpumask_bits; + if (cpu_paravirt(prev_cpu)) + return this_cpu; + if (sched_feat(WA_IDLE)) target = wake_affine_idle(this_cpu, prev_cpu, sync); @@ -7441,6 +7444,11 @@ static inline int sched_balance_find_dst_cpu(struct sched_domain *sd, struct tas { int new_cpu = cpu; + if (cpu_paravirt(prev_cpu)) { + schedstat_inc(p->stats.nr_wakeups_paravirt); + return cpu; + } + if (!cpumask_intersects(sched_domain_span(sd), p->cpus_ptr)) return prev_cpu; @@ -7777,10 +7785,25 @@ static int select_idle_sibling(struct task_struct *p, int this_cpu, int prev, in unsigned long task_util, util_min, util_max; int i, recent_used_cpu, prev_aff = -1; + /* Likely prev,target belong to same LLC, it is better at wakeup + * to move away from them. at best return recent_used_cpu if it + * is usable + */ + if (cpu_paravirt(prev) || cpu_paravirt(target)) { + schedstat_inc(p->stats.nr_wakeups_paravirt); + + recent_used_cpu = p->recent_used_cpu; + if (!cpu_paravirt(recent_used_cpu)) + return recent_used_cpu; + else + return this_cpu; + } + /* * On asymmetric system, update task utilization because we will check * that the task fits with CPU's capacity. */ + if (sched_asym_cpucap_active()) { sync_entity_load_avg(&p->se); task_util = task_util_est(p); @@ -8539,8 +8562,14 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) if (!is_rd_overutilized(this_rq()->rd)) { new_cpu = find_energy_efficient_cpu(p, prev_cpu); - if (new_cpu >= 0) + + /* System supporting Energy model isn't expected + * have a CPU marked as paravirt + */ + if (new_cpu >= 0) { + WARN_ON_ONCE(cpu_paravirt(new_cpu)); return new_cpu; + } new_cpu = prev_cpu; } @@ -11832,6 +11861,11 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq, cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); +#ifdef CONFIG_PARAVIRT + /* Don't spread load to paravirt CPUs */ + cpumask_andnot(cpus, cpus, cpu_paravirt_mask); +#endif + schedstat_inc(sd->lb_count[idle]); redo: -- 2.47.3
