| Message ID | 20140211164136.GT27965@twins.programming.kicks-ass.net (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On 2/11/2014 8:41 AM, Peter Zijlstra wrote: > On Mon, Feb 03, 2014 at 08:17:47AM -0800, Arjan van de Ven wrote: >> On 2/3/2014 6:56 AM, Peter Zijlstra wrote: >> if there's a simple api like >> >> sched_cpu_cache_wiped(int llc) >> >> that would be very nice for this; the menuidle side knows this >> for some cases and thus can just call it. This would be a very >> small and minimal change >> >> * if you don't care about llc vs core local caches then that >> parameter can go away >> >> * I assume this is also called for the local cpu... if not then we >> need to add a cpu number argument >> >> * we can also call this from architecture code when wbinvd or the >> arm equivalent is called etc > > A little something like so? > is there value also in doing a cpu level cache flush? (cpu cache flush we know from the C state, for the llc cache flush we need to read an MSR on x86. Not insane expensive but not zero either) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Feb 11, 2014 at 09:12:02AM -0800, Arjan van de Ven wrote: > On 2/11/2014 8:41 AM, Peter Zijlstra wrote: > >On Mon, Feb 03, 2014 at 08:17:47AM -0800, Arjan van de Ven wrote: > >>On 2/3/2014 6:56 AM, Peter Zijlstra wrote: > >>if there's a simple api like > >> > >>sched_cpu_cache_wiped(int llc) > >> > >>that would be very nice for this; the menuidle side knows this > >>for some cases and thus can just call it. This would be a very > >>small and minimal change > >> > >>* if you don't care about llc vs core local caches then that > >> parameter can go away > >> > >>* I assume this is also called for the local cpu... if not then we > >> need to add a cpu number argument > >> > >>* we can also call this from architecture code when wbinvd or the > >> arm equivalent is called etc > > > >A little something like so? > > > > is there value also in doing a cpu level cache flush? > (cpu cache flush we know from the C state, for the llc cache flush we need to read an MSR > on x86. Not insane expensive but not zero either) L1 or L2? L1 is too small to really bother afaik and L2 is shared between logical cpus so we'd need a mask there, not sure the generic topology has that. I'll have a quick peek later. -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index fb9764fbc537..b06bcadc6d71 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5466,6 +5466,27 @@ static void update_top_cache_domain(int cpu) } /* + * Mark the current LLC as empty. + */ +void sched_llc_wipe_cache(void) +{ + struct sched_domain *sd; + + rcu_read_lock(); + sd = rcu_dereference(__get_cpu_var(sd_llc)); + if (sd) { + int cpu; + + for_each_cpu(cpu, sched_domain_span(sd)) { + struct rq *rq = cpu_rq(cpu); + + rq->llc_wiped = sched_clock_cpu(cpu); + } + } + rcu_read_unlock(); +} + +/* * Attach the domain 'sd' to 'cpu' as its base domain. Callers must * hold the hotplug lock. */ diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 235cfa7ad8fc..9f8ce98f8131 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5025,9 +5025,10 @@ static void move_task(struct task_struct *p, struct lb_env *env) /* * Is this task likely cache-hot: */ -static int -task_hot(struct task_struct *p, u64 now, struct sched_domain *sd) +static int task_hot(struct task_struct *p, struct lb_env *env) { + u64 now = rq_clock_task(env->src_rq); + struct sched_domain *sd = env->sd; s64 delta; if (p->sched_class != &fair_sched_class) @@ -5049,6 +5050,12 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd) if (sysctl_sched_migration_cost == 0) return 0; + /* + * If its LLC got wiped after it ran last, we're as cold as it gets. + */ + if ((s64)(p->se.exec_start - env->src_rq->llc_wiped) < 0) + return 0; + delta = now - p->se.exec_start; return delta < (s64)sysctl_sched_migration_cost; @@ -5187,7 +5194,7 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) * 2) task is cache cold, or * 3) too many balance attempts have failed. */ - tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd); + tsk_cache_hot = task_hot(p, env); if (!tsk_cache_hot) tsk_cache_hot = migrate_degrades_locality(p, env); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 1bf34c257d3b..c98793112614 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -582,6 +582,7 @@ struct rq { struct list_head cfs_tasks; + u64 llc_wiped; u64 rt_avg; u64 age_stamp; u64 idle_stamp;