From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>,
Will Deacon <will@kernel.org>
Cc: Darren Hart <darren@os.amperecomputing.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Arm <linux-arm-kernel@lists.infradead.org>,
Sudeep Holla <sudeep.holla@arm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J. Wysocki" <rafael@kernel.org>,
Catalin Marinas <Catalin.Marinas@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Barry Song <song.bao.hua@hisilicon.com>,
Valentin Schneider <Valentin.Schneider@arm.com>,
"D . Scott Phillips" <scott@os.amperecomputing.com>,
Ilkka Koskinen <ilkka@os.amperecomputing.com>,
stable@vger.kernel.org
Subject: Re: [PATCH v3] topology: make core_mask include at least cluster_siblings
Date: Tue, 8 Mar 2022 17:03:07 +0100 [thread overview]
Message-ID: <e91bcc83-37c8-dcca-e088-8b3fcd737b2c@arm.com> (raw)
In-Reply-To: <CAKfTPtDe+i0fwV10m2sX2xkJGBrO8B+RQogDDij8ioJAT5+wAw@mail.gmail.com>
On 08/03/2022 12:04, Vincent Guittot wrote:
> On Tue, 8 Mar 2022 at 11:30, Will Deacon <will@kernel.org> wrote:
[...]
>>> ---
>>> v1: Drop MC level if coregroup weight == 1
>>> v2: New sd topo in arch/arm64/kernel/smp.c
>>> v3: No new topo, extend core_mask to cluster_siblings
>>>
>>> drivers/base/arch_topology.c | 8 ++++++++
>>> 1 file changed, 8 insertions(+)
>>>
>>> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
>>> index 976154140f0b..a96f45db928b 100644
>>> --- a/drivers/base/arch_topology.c
>>> +++ b/drivers/base/arch_topology.c
>>> @@ -628,6 +628,14 @@ const struct cpumask *cpu_coregroup_mask(int cpu)
>>> core_mask = &cpu_topology[cpu].llc_sibling;
>>> }
>>>
>>> + /*
>>> + * For systems with no shared cpu-side LLC but with clusters defined,
>>> + * extend core_mask to cluster_siblings. The sched domain builder will
>>> + * then remove MC as redundant with CLS if SCHED_CLUSTER is enabled.
IMHO, if core_mask weight is 1, MC will be removed/degenerated anyway.
This is what I get on my Ampere Altra (I guess I don't have the ACPI
changes which would let to a CLS sched domain):
# cat /sys/kernel/debug/sched/domains/cpu0/domain*/name
DIE
NUMA
root@oss-altra01:~# zcat /proc/config.gz | grep SCHED_CLUSTER
CONFIG_SCHED_CLUSTER=y
>>> + */
>>> + if (cpumask_subset(core_mask, &cpu_topology[cpu].cluster_sibling))
>>> + core_mask = &cpu_topology[cpu].cluster_sibling;
>>> +
>>
>> Sudeep, Vincent, are you happy with this now?
>
> I would not say that I'm happy because this solution skews the core
> cpu mask in order to abuse the scheduler so that it will remove a
> wrong but useless level when it will build its domains.
> But this works so as long as the maintainer are happy, I'm fine
I do not have any better idea than this tweak here either in case the
platform can't provide a cleaner setup.
Maybe the following is easier to read but then we use
'&cpu_topology[cpu].llc_sibling' in cpu_coregroup_mask() already ...
@@ -617,6 +617,7 @@ EXPORT_SYMBOL_GPL(cpu_topology);
const struct cpumask *cpu_coregroup_mask(int cpu)
{
const cpumask_t *core_mask = cpumask_of_node(cpu_to_node(cpu));
+ const cpumask_t *cluster_mask = cpu_clustergroup_mask(cpu);
/* Find the smaller of NUMA, core or LLC siblings */
if (cpumask_subset(&cpu_topology[cpu].core_sibling, core_mask)) {
@@ -628,6 +629,9 @@ const struct cpumask *cpu_coregroup_mask(int cpu)
core_mask = &cpu_topology[cpu].llc_sibling;
}
+ if (cpumask_subset(core_mask, cluster_mask))
+ core_mask = cluster_mask;
+
return core_mask;
}
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
next prev parent reply other threads:[~2022-03-08 16:03 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-04 17:01 [PATCH v3] topology: make core_mask include at least cluster_siblings Darren Hart
2022-03-08 10:30 ` Will Deacon
2022-03-08 10:45 ` Sudeep Holla
2022-03-08 11:04 ` Vincent Guittot
2022-03-08 16:03 ` Dietmar Eggemann [this message]
2022-03-08 17:49 ` Darren Hart
2022-03-09 12:50 ` Dietmar Eggemann
2022-03-09 18:26 ` Darren Hart
2022-03-14 9:37 ` Dietmar Eggemann
2022-03-14 16:56 ` Darren Hart
2022-03-16 14:42 ` Dietmar Eggemann
2022-03-14 16:35 ` Dietmar Eggemann
2022-03-14 16:54 ` Darren Hart
2022-03-16 14:48 ` Dietmar Eggemann
2022-03-16 15:20 ` Darren Hart
2022-03-16 15:55 ` Sudeep Holla
2022-03-21 14:30 ` Will Deacon
2022-03-21 15:56 ` Greg Kroah-Hartman
2022-03-14 21:29 ` [PATCH] arch_topology: Swap MC & CLS SD mask if MC weight==1 & kernel test robot
2022-03-14 23:02 ` kernel test robot
2022-03-17 6:10 ` [PATCH v3] topology: make core_mask include at least cluster_siblings Barry Song
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