From: Valentin Schneider <valentin.schneider@arm•com>
To: Morten Rasmussen <morten.rasmussen@arm•com>
Cc: Len Brown <len.brown@intel•com>,
Sudeep Holla <sudeep.holla@arm•com>,
Peter Zijlstra <peterz@infradead•org>,
Greg Kroah-Hartman <gregkh@linuxfoundation•org>,
x86@kernel•org, guohanjun@huawei•com,
linux-kernel@vger•kernel.org,
Jeremy Linton <Jeremy.Linton@arm•com>,
linuxarm@huawei•com, Brice Goglin <Brice.Goglin@inria•fr>,
linux-acpi@vger•kernel.org,
Jonathan Cameron <Jonathan.Cameron@Huawei•com>,
Will Deacon <will@kernel•org>,
linux-arm-kernel@lists•infradead.org
Subject: Re: [RFC PATCH] topology: Represent clusters of CPUs within a die.
Date: Mon, 19 Oct 2020 14:48:02 +0100 [thread overview]
Message-ID: <jhjh7qqqqct.mognet@arm.com> (raw)
In-Reply-To: <20201019131052.GC8004@e123083-lin>
+Cc Jeremy
On 19/10/20 14:10, Morten Rasmussen wrote:
> Hi Jonathan,
> The problem I see is that the benefit of keeping tasks together due to
> the interconnect layout might vary significantly between systems. So if
> we introduce a new cpumask for cluster it has to have represent roughly
> the same system properties otherwise generic software consuming this
> information could be tricked.
>
> 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.
>
> Morten
That's my queue to paste some of that stuff I've been rambling on and off
about!
With regards to cache / interconnect layout, I do believe that if we
want to support in the scheduler itself then we should leverage some
distance table rather than to create X extra scheduler topology levels.
I had a chat with Jeremy on the ACPI side of that sometime ago. IIRC given
that SLIT gives us a distance value between any two PXM, we could directly
express core-to-core distance in that table. With that (and if that still
lets us properly discover NUMA node spans), we could let the scheduler
build dynamic NUMA-like topology levels representing the inner quirks of
the cache / interconnect layout.
It's mostly pipe dreams for now, but there seems to be more and more
hardware where that would make sense; somewhat recently the PowerPC guys
added something to their arch-specific code in that regards.
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next prev parent reply other threads:[~2020-10-19 13:49 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
2020-10-19 15:30 ` Jonathan Cameron
2020-10-19 13:48 ` Valentin Schneider [this message]
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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