From: peterz@infradead.org
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Mel Gorman <mgorman@techsingularity.net>,
Rik van Riel <riel@surriel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Valentin Schneider <valentin.schneider@arm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Michael Neuling <mikey@neuling.org>,
Gautham R Shenoy <ego@linux.vnet.ibm.com>,
Vaidyanathan Srinivasan <svaidy@linux.ibm.com>
Subject: Re: [PATCH 2/2] powerpc/topology: Override cpu_smt_mask
Date: Tue, 4 Aug 2020 12:46:42 +0200 [thread overview]
Message-ID: <20200804104642.GC2657@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200804033307.76111-2-srikar@linux.vnet.ibm.com>
On Tue, Aug 04, 2020 at 09:03:07AM +0530, Srikar Dronamraju wrote:
> On Power9 a pair of cores can be presented by the firmware as a big-core
> for backward compatibility reasons, with 4 threads per (small) core and 8
> threads per big-core. cpu_smt_mask() should generally point to the cpu mask
> of the (small)core.
>
> In order to maintain userspace backward compatibility (with Power8 chips in
> case of Power9) in enterprise Linux systems, the topology_sibling_cpumask
> has to be set to big-core. Hence override the default cpu_smt_mask() to be
> powerpc specific allowing for better scheduling behaviour on Power.
Why does Linux userspace care about this?
next prev parent reply other threads:[~2020-08-04 10:48 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-04 3:33 [PATCH 1/2] sched/topology: Allow archs to override cpu_smt_mask Srikar Dronamraju
2020-08-04 3:33 ` [PATCH 2/2] powerpc/topology: Override cpu_smt_mask Srikar Dronamraju
2020-08-04 10:46 ` peterz [this message]
2020-08-04 11:02 ` Valentin Schneider
2020-08-04 10:45 ` [PATCH 1/2] sched/topology: Allow archs to override cpu_smt_mask peterz
2020-08-04 12:10 ` Srikar Dronamraju
2020-08-04 12:47 ` peterz
2020-08-06 5:32 ` Michael Ellerman
2020-08-06 8:54 ` peterz
2020-08-06 12:25 ` Michael Ellerman
2020-08-06 13:15 ` peterz
2020-08-06 14:09 ` Srikar Dronamraju
2020-08-06 12:53 ` Srikar Dronamraju
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