Messages in this thread Patch in this message | | | Date | Fri, 12 Jun 2020 09:21:27 -0400 | From | Joel Fernandes <> | Subject | Re: [RFC PATCH 11/13] sched: migration changes for core scheduling |
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On Wed, Mar 04, 2020 at 05:00:01PM +0000, vpillai wrote: > From: Aubrey Li <aubrey.li@intel.com> > > - Don't migrate if there is a cookie mismatch > Load balance tries to move task from busiest CPU to the > destination CPU. When core scheduling is enabled, if the > task's cookie does not match with the destination CPU's > core cookie, this task will be skipped by this CPU. This > mitigates the forced idle time on the destination CPU. > > - Select cookie matched idle CPU > In the fast path of task wakeup, select the first cookie matched > idle CPU instead of the first idle CPU. > > - Find cookie matched idlest CPU > In the slow path of task wakeup, find the idlest CPU whose core > cookie matches with task's cookie > > - Don't migrate task if cookie not match > For the NUMA load balance, don't migrate task to the CPU whose > core cookie does not match with task's cookie > > Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com> > Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> > Signed-off-by: Vineeth Remanan Pillai <vpillai@digitalocean.com> > --- > kernel/sched/fair.c | 55 +++++++++++++++++++++++++++++++++++++++++--- > kernel/sched/sched.h | 29 +++++++++++++++++++++++ > 2 files changed, 81 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 1c9a80d8dbb8..f42ceecb749f 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -1789,6 +1789,15 @@ static void task_numa_find_cpu(struct task_numa_env *env, > if (!cpumask_test_cpu(cpu, env->p->cpus_ptr)) > continue; > > +#ifdef CONFIG_SCHED_CORE > + /* > + * Skip this cpu if source task's cookie does not match > + * with CPU's core cookie. > + */ > + if (!sched_core_cookie_match(cpu_rq(cpu), env->p)) > + continue; > +#endif > + > env->dst_cpu = cpu; > task_numa_compare(env, taskimp, groupimp, maymove); > } > @@ -5660,8 +5669,13 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this > > /* Traverse only the allowed CPUs */ > for_each_cpu_and(i, sched_group_span(group), p->cpus_ptr) { > + struct rq *rq = cpu_rq(i); > + > +#ifdef CONFIG_SCHED_CORE > + if (!sched_core_cookie_match(rq, p)) > + continue; > +#endif > if (available_idle_cpu(i)) { > - struct rq *rq = cpu_rq(i); > struct cpuidle_state *idle = idle_get_state(rq); > if (idle && idle->exit_latency < min_exit_latency) { > /* > @@ -5927,8 +5941,14 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > return si_cpu; > if (!cpumask_test_cpu(cpu, p->cpus_ptr)) > continue; > +#ifdef CONFIG_SCHED_CORE > + if (available_idle_cpu(cpu) && > + sched_core_cookie_match(cpu_rq(cpu), p)) > + break; > +#else
select_idle_cpu() is called only if no idle core could be found in the LLC by select_idle_core().
So, would it be better here to just do the cookie equality check directly instead of calling the sched_core_cookie_match() helper? More so, because select_idle_sibling() is a fastpath.
AFAIR, that's what v4 did:
if (available_idle_cpu(cpu)) #ifdef CONFIG_SCHED_CORE if (sched_core_enabled(cpu_rq(cpu)) && (p->core_cookie == cpu_rq(cpu)->core->core_cookie)) break; #else break; #endif
Thoughts? thanks,
- Joel
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