From: peterz@infradead•org
To: Srikar Dronamraju <srikar@linux•vnet.ibm.com>
Cc: Gautham R Shenoy <ego@linux•vnet.ibm.com>,
Michael Neuling <mikey@neuling•org>,
Vincent Guittot <vincent.guittot@linaro•org>,
Rik van Riel <riel@surriel•com>,
linuxppc-dev <linuxppc-dev@lists•ozlabs.org>,
LKML <linux-kernel@vger•kernel.org>,
Ingo Molnar <mingo@kernel•org>,
Thomas Gleixner <tglx@linutronix•de>,
Mel Gorman <mgorman@techsingularity•net>,
Valentin Schneider <valentin.schneider@arm•com>,
Dietmar Eggemann <dietmar.eggemann@arm•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 10:49 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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