From: Brice Goglin <Brice.Goglin@inria.fr>
To: Morten Rasmussen <morten.rasmussen@arm.com>,
Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Cc: Len Brown <len.brown@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
x86@kernel.org, guohanjun@huawei.com,
linux-kernel@vger.kernel.org, linuxarm@huawei.com,
linux-acpi@vger.kernel.org, Jerome Glisse <jglisse@redhat.com>,
Sudeep Holla <sudeep.holla@arm.com>,
Will Deacon <will@kernel.org>,
valentin.schneider@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH] topology: Represent clusters of CPUs within a die.
Date: Mon, 19 Oct 2020 16:42:24 +0200 [thread overview]
Message-ID: <0190e18f-7a55-e1d6-b966-f7844a251609@inria.fr> (raw)
In-Reply-To: <20201019141653.GE8004@e123083-lin>
Le 19/10/2020 à 16:16, Morten Rasmussen a écrit :
>
>>> If there is a provable benefit of having interconnect grouping
>>> information, I think it would be better represented by a distance matrix
>>> like we have for NUMA.
>> There have been some discussions in various forums about how to
>> describe the complexity of interconnects well enough to actually be
>> useful. Those have mostly floundered on the immense complexity of
>> designing such a description in a fashion any normal software would actually
>> use. +cc Jerome who raised some of this in the kernel a while back.
> I agree that representing interconnect details is hard. I had hoped that
> a distance matrix would be better than nothing and more generic than
> inserting extra group masks.
>
The distance matrix is indeed more precise, but would it scale to
tens/hundreds of core? When ACPI HMAT latency/bandwidth was added, there
were concerns that exposing the full matrix would be an issue for the
kernel (that's why only local latency/bandwidth is exposed n sysfs).
This was only for NUMA nodes/targets/initiators, you would have
significantly more cores than that.
Brice
next prev parent reply other threads:[~2020-10-19 14:42 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-16 15:27 [RFC PATCH] topology: Represent clusters of CPUs within a die Jonathan Cameron
2020-10-17 6:44 ` Greg Kroah-Hartman
2020-10-19 8:08 ` Jonathan Cameron
2020-10-19 10:00 ` Brice Goglin
2020-10-19 12:38 ` Jonathan Cameron
2020-10-19 10:01 ` Sudeep Holla
2020-10-19 13:14 ` Jonathan Cameron
2020-10-19 10:35 ` Peter Zijlstra
2020-10-19 12:32 ` Jonathan Cameron
2020-10-19 12:50 ` Peter Zijlstra
2020-10-19 13:12 ` Brice Goglin
2020-10-19 13:13 ` Morten Rasmussen
2020-10-19 13:10 ` Morten Rasmussen
2020-10-19 13:41 ` Jonathan Cameron
2020-10-19 14:16 ` Morten Rasmussen
2020-10-19 14:42 ` Brice Goglin [this message]
2020-10-19 15:30 ` Jonathan Cameron
2020-10-19 13:48 ` Valentin Schneider
2020-10-19 14:27 ` Jonathan Cameron
2020-10-19 15:51 ` Valentin Schneider
2020-10-19 16:00 ` Jonathan Cameron
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