From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Len Brown <len.brown@intel.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Ricardo Neri <ricardo.neri@intel.com>,
Quentin Perret <qperret@google.com>,
"Joel Fernandes (Google)" <joel@joelfernandes.org>,
linux-kernel@vger.kernel.org, Aubrey Li <aubrey.li@intel.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>
Subject: Re: [PATCH v3 5/6] sched/fair: Consider SMT in ASYM_PACKING load balance
Date: Fri, 14 May 2021 19:14:15 -0700 [thread overview]
Message-ID: <20210515021415.GB14212@ranerica-svr.sc.intel.com> (raw)
In-Reply-To: <YJ5HQR943rSFsLxw@hirez.programming.kicks-ass.net>
On Fri, May 14, 2021 at 11:47:45AM +0200, Peter Zijlstra wrote:
> On Thu, May 13, 2021 at 08:49:08AM -0700, Ricardo Neri wrote:
> > include/linux/sched/topology.h | 1 +
> > kernel/sched/fair.c | 101 +++++++++++++++++++++++++++++++++
> > 2 files changed, 102 insertions(+)
> >
> > diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> > index 8f0f778b7c91..43bdb8b1e1df 100644
> > --- a/include/linux/sched/topology.h
> > +++ b/include/linux/sched/topology.h
> > @@ -57,6 +57,7 @@ static inline int cpu_numa_flags(void)
> > #endif
> >
> > extern int arch_asym_cpu_priority(int cpu);
> > +extern bool arch_asym_check_smt_siblings(void);
> >
> > struct sched_domain_attr {
> > int relax_domain_level;
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index c8b66a5d593e..3d6cc027e6e6 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -106,6 +106,15 @@ int __weak arch_asym_cpu_priority(int cpu)
> > return -cpu;
> > }
> >
> > +/*
> > + * For asym packing, first check the state of SMT siblings before deciding to
> > + * pull tasks.
> > + */
> > +bool __weak arch_asym_check_smt_siblings(void)
> > +{
> > + return false;
> > +}
> > +
> > /*
> > * The margin used when comparing utilization with CPU capacity.
> > *
>
> > @@ -8458,6 +8550,9 @@ sched_asym(struct lb_env *env, struct sd_lb_stats *sds, struct sg_lb_stats *sgs
> > if (group == sds->local)
> > return false;
> >
> > + if (arch_asym_check_smt_siblings())
> > + return asym_can_pull_tasks(env->dst_cpu, sds, sgs, group);
> > +
> > return sched_asym_prefer(env->dst_cpu, group->asym_prefer_cpu);
> > }
>
> So I'm thinking that this is a property of having ASYM_PACKING at a core
> level, rather than some arch special. Wouldn't something like this be
> more appropriate?
>
> ---
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -57,7 +57,6 @@ static inline int cpu_numa_flags(void)
> #endif
>
> extern int arch_asym_cpu_priority(int cpu);
> -extern bool arch_asym_check_smt_siblings(void);
>
> struct sched_domain_attr {
> int relax_domain_level;
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -107,15 +107,6 @@ int __weak arch_asym_cpu_priority(int cp
> }
>
> /*
> - * For asym packing, first check the state of SMT siblings before deciding to
> - * pull tasks.
> - */
> -bool __weak arch_asym_check_smt_siblings(void)
> -{
> - return false;
> -}
> -
> -/*
> * The margin used when comparing utilization with CPU capacity.
> *
> * (default: ~20%)
> @@ -8550,7 +8541,8 @@ sched_asym(struct lb_env *env, struct sd
> if (group == sds->local)
> return false;
>
> - if (arch_asym_check_smt_siblings())
> + if ((sds->local->flags & SD_SHARE_CPUCAPACITY) ||
> + (group->flags & SD_SHARE_CPUCAPACITY))
> return asym_can_pull_tasks(env->dst_cpu, sds, sgs, group);
Thanks Peter for the quick review! This makes sense to me. The only
reason we proposed arch_asym_check_smt_siblings() is because we were
about breaking powerpc (I need to study how they set priorities for SMT,
if applicable). If you think this is not an issue I can post a
v4 with this update.
Thanks and BR,
Ricardo
next prev parent reply other threads:[~2021-05-15 2:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 15:49 [PATCH v3 0/6] sched/fair: Fix load balancing of SMT siblings with ASYM_PACKING Ricardo Neri
2021-05-13 15:49 ` [PATCH v3 1/6] sched/topology: Introduce sched_group::flags Ricardo Neri
2021-05-13 15:49 ` [PATCH v3 2/6] sched/fair: Optimize checking for group_asym_packing Ricardo Neri
2021-05-13 15:49 ` [PATCH v3 3/6] sched/fair: Provide update_sg_lb_stats() with sched domain statistics Ricardo Neri
2021-05-13 15:49 ` [PATCH v3 4/6] sched/fair: Carve out logic to mark a group for asymmetric packing Ricardo Neri
2021-05-17 14:21 ` Dietmar Eggemann
2021-05-18 19:18 ` Ricardo Neri
2021-05-13 15:49 ` [PATCH v3 5/6] sched/fair: Consider SMT in ASYM_PACKING load balance Ricardo Neri
2021-05-14 9:47 ` Peter Zijlstra
2021-05-15 2:14 ` Ricardo Neri [this message]
2021-05-18 19:07 ` Ricardo Neri
2021-05-19 9:59 ` Peter Zijlstra
2021-05-19 11:09 ` Nicholas Piggin
2021-05-19 12:05 ` Srikar Dronamraju
2021-05-17 15:18 ` Dietmar Eggemann
2021-05-18 19:10 ` Ricardo Neri
2021-05-17 22:28 ` Joel Fernandes
2021-05-17 22:34 ` Joel Fernandes
2021-05-13 15:49 ` [PATCH v3 6/6] x86/sched: Enable SMT checks for asymmetric packing in load balancing Ricardo Neri
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