From: Joel Fernandes <joel@joelfernandes.org>
To: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
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>,
LKML <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: Mon, 17 May 2021 18:34:07 -0400 [thread overview]
Message-ID: <CAEXW_YQZiV6tQC-UNoRujWDes-zF91BC1GvxBYoEKfPABZEYhA@mail.gmail.com> (raw)
In-Reply-To: <YKLuJHcqea/zU1H1@google.com>
On Mon, May 17, 2021 at 6:28 PM Joel Fernandes <joel@joelfernandes.org> wrote:
>
> On Thu, May 13, 2021 at 08:49:08AM -0700, Ricardo Neri wrote:
> > When deciding to pull tasks in ASYM_PACKING, it is necessary not only to
> > check for the idle state of the destination CPU, dst_cpu, but also of
> > its SMT siblings.
> >
[...]
> > + if (!local_is_smt) {
> > + /*
> > + * If we are here, @dst_cpu is idle and does not have SMT
> > + * siblings. Pull tasks if candidate group has two or more
> > + * busy CPUs.
> > + */
> > + if (sg_is_smt && sg_busy_cpus >= 2)
> > + return true;
> > +
> > + /*
> > + * @dst_cpu does not have SMT siblings. @sg may have SMT
> > + * siblings and only one is busy. In such case, @dst_cpu
> > + * can help if it has higher priority and is idle.
> > + */
> > + return !sds->local_stat.group_util &&
> > + sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu);
> > + }
> > +
> > + /* @dst_cpu has SMT siblings. */
> > +
> > + local_busy_cpus = sds->local->group_weight - sds->local_stat.idle_cpus;
> > +
> > + if (sg_is_smt) {
> > + int busy_cpus_delta = sg_busy_cpus - local_busy_cpus;
> > +
> > + /* Local can always help to even the number busy CPUs. */
> > + if (busy_cpus_delta >= 2)
> > + return true;
> > +
> > + if (busy_cpus_delta == 1)
> > + return sched_asym_prefer(dst_cpu,
> > + sg->asym_prefer_cpu);
> > +
> > + return false;
> > + }
> > +
> > + /*
> > + * @sg does not have SMT siblings. Ensure that @sds::local does not end
> > + * up with more than one busy SMT sibling and only pull tasks if there
> > + * are not busy CPUs. As CPUs move in and out of idle state frequently,
> > + * also check the group utilization to smoother the decision.
>
> nit: s/smoother/smoothen/
>
> > + */
> > + if (!local_busy_cpus && !sds->local_stat.group_util)
> > + return sched_asym_prefer(dst_cpu, sg->asym_prefer_cpu);
>
> Hmm, I am not sure but is it possible that there some local_busy_cpus yet
> group_util is 0? If not just check for !group_util ?
Sorry - I meant here, "yet group_util is not 0..."
next prev parent reply other threads:[~2021-05-17 22:34 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
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 [this message]
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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