From: Peter Zijlstra <peterz@infradead.org>
To: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Len Brown <len.brown@intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
x86@kernel.org, guohanjun@huawei.com,
linux-kernel@vger.kernel.org, linuxarm@huawei.com,
Brice Goglin <Brice.Goglin@inria.fr>,
linux-acpi@vger.kernel.org, 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 12:35:22 +0200 [thread overview]
Message-ID: <20201019103522.GK2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201016152702.1513592-1-Jonathan.Cameron@huawei.com>
On Fri, Oct 16, 2020 at 11:27:02PM +0800, Jonathan Cameron wrote:
> Both ACPI and DT provide the ability to describe additional layers of
> topology between that of individual cores and higher level constructs
> such as the level at which the last level cache is shared.
> In ACPI this can be represented in PPTT as a Processor Hierarchy
> Node Structure [1] that is the parent of the CPU cores and in turn
> has a parent Processor Hierarchy Nodes Structure representing
> a higher level of topology.
>
> For example Kunpeng 920 has clusters of 4 CPUs. These do not share
> any cache resources, but the interconnect topology is such that
> the cost to transfer ownership of a cacheline between CPUs within
> a cluster is lower than between CPUs in different clusters on the same
> die. Hence, it can make sense to deliberately schedule threads
> sharing data to a single cluster.
>
> This patch simply exposes this information to userspace libraries
> like hwloc by providing cluster_cpus and related sysfs attributes.
> PoC of HWLOC support at [2].
>
> Note this patch only handle the ACPI case.
>
> Special consideration is needed for SMT processors, where it is
> necessary to move 2 levels up the hierarchy from the leaf nodes
> (thus skipping the processor core level).
I'm confused by all of this. The core level is exactly what you seem to
want.
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next prev parent reply other threads:[~2020-10-19 10:36 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 [this message]
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
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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