From: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
To: Valentin Schneider <vschneid@redhat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Ricardo Neri <ricardo.neri@intel.com>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Ben Segall <bsegall@google.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Len Brown <len.brown@intel.com>, Mel Gorman <mgorman@suse.de>,
"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Steven Rostedt <rostedt@goodmis.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
"Tim C . Chen" <tim.c.chen@intel.com>
Subject: Re: [PATCH v2 1/7] sched/fair: Generalize asym_packing logic for SMT local sched group
Date: Tue, 17 Jan 2023 04:49:28 -0800 [thread overview]
Message-ID: <20230117124928.GA5559@ranerica-svr.sc.intel.com> (raw)
In-Reply-To: <xhsmhtu0qi9h1.mognet@vschneid.remote.csb>
On Mon, Jan 16, 2023 at 07:07:54PM +0000, Valentin Schneider wrote:
> On 15/01/23 20:05, Ricardo Neri wrote:
> >> >
> >> > It should be set on any topology level below the NUMA ones, we do remove it
> >> > on SD_ASYM_CPUCAPACITY levels because this used to interfere with misfit
> >> > balancing (it would override the group_type), things are a bit different
> >> > since Vincent's rewrite of load_balance() but I think we still want it off
> >> > there.
> >
> > Your comment got me thinking. Whose child sched domain wants prefer_sibling?
> > It sounds to me that is busiest's. I could not think of any reason of *having*
> > to use the flags of the local group.
> >
>
> Hm, given that on systems without SD_ASYM_CPUCAPACITY, SD_PREFER_SIBLING is
> set all the way from SMT up to the last !NUMA domain, should we just get
> rid of the child/parent weirdness of SD_PREFER_SIBLING and stick with the
> flags we are given at the level we're balancing at?
>
> i.e.
>
> sds->prefer_sibling = env->sd & SD_PREFER_SIBLING;
Agreed. This would also make the code easier to understand. It should not change
the current behavior either; except (i.e., fix) for the busiest->group_weight = 2
vs local->group_weight = 1 I raised.
>
> Unless I'm reading this wrong, this also eliminates the effect of
> SD_PREFER_SIBLING on the first NUMA level - DIE level has SD_PREFER_SIBLING
> set, but we don't necessarily want to evenly spread things out when accross
> NUMA nodes.
Agreed.
>
>
> > We can use the flags of the sched group (as per 16d364ba6ef2 ("sched/topology:
> > Introduce sched_group::flags"), these are the flags of the child domain).
> >
> > The patch below works for me and I don't have to even the number of busy CPUs.
> > It should not interfere with misfit balancing either:
> >
>
> We remove that flag on systems where misfit balancing happens anyway, so
> that's safe vs. SD_PREFER_SIBLING.
Then all looks good with your suggestion. I'll include a patch in my series.
Thanks and BR,
Ricardo
next prev parent reply other threads:[~2023-01-17 12:40 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-22 20:35 [PATCH v2 0/7] x86/sched: Avoid unnecessary migrations within SMT domains Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 1/7] sched/fair: Generalize asym_packing logic for SMT local sched group Ricardo Neri
2022-12-06 17:22 ` Dietmar Eggemann
2022-12-12 17:53 ` Ricardo Neri
2022-12-21 13:03 ` Dietmar Eggemann
2022-12-22 4:32 ` Ricardo Neri
2022-12-22 11:12 ` Dietmar Eggemann
2022-12-23 13:11 ` Ricardo Neri
2022-12-22 16:55 ` Valentin Schneider
2022-12-29 4:00 ` Ricardo Neri
2023-01-11 16:04 ` Valentin Schneider
2023-01-13 19:02 ` Ricardo Neri
2023-01-16 4:05 ` Ricardo Neri
2023-01-16 19:07 ` Valentin Schneider
2023-01-17 12:49 ` Ricardo Neri [this message]
2022-11-22 20:35 ` [PATCH v2 2/7] sched: Prepare sched_asym_prefer() to handle idle state of SMT siblings Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 3/7] sched: Teach arch_asym_cpu_priority() the " Ricardo Neri
2022-12-06 17:54 ` Dietmar Eggemann
2022-12-12 17:54 ` Ricardo Neri
2022-12-21 17:12 ` Dietmar Eggemann
2022-12-22 4:55 ` Ricardo Neri
2022-12-22 16:56 ` Valentin Schneider
2022-11-22 20:35 ` [PATCH v2 4/7] sched/fair: Introduce sched_smt_siblings_idle() Ricardo Neri
2022-12-06 18:03 ` Dietmar Eggemann
2022-12-12 17:54 ` Ricardo Neri
2022-12-22 11:12 ` Dietmar Eggemann
2022-12-22 16:56 ` Valentin Schneider
2022-12-24 5:28 ` Ricardo Neri
2022-12-28 15:29 ` Chen Yu
2022-12-30 0:17 ` Ricardo Neri
2023-01-10 19:21 ` Valentin Schneider
2022-11-22 20:35 ` [PATCH v2 5/7] x86/sched: Remove SD_ASYM_PACKING from the "SMT" domain Ricardo Neri
2022-12-08 16:03 ` Ionela Voinescu
2022-12-14 16:59 ` Ricardo Neri
2022-12-15 16:48 ` Valentin Schneider
2022-12-20 0:42 ` Ricardo Neri
2022-12-22 16:56 ` Valentin Schneider
2022-12-29 19:02 ` Ricardo Neri
2023-01-10 19:17 ` Valentin Schneider
2023-01-13 1:31 ` Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 6/7] x86/sched/itmt: Give all SMT siblings of a core the same priority Ricardo Neri
2022-11-22 20:35 ` [PATCH v2 7/7] x86/sched/itmt: Consider the idle state of SMT siblings Ricardo Neri
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