From: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Mark Rutland <mark.rutland@arm.com>,
Valentin Schneider <vschneid@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
"ndesaulniers@google.com" <ndesaulniers@google.com>,
linux-kernel@vger.kernel.org,
Rohan McLure <rmclure@linux.ibm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Josh Poimboeuf <jpoimboe@kernel.org>
Subject: Re: [PATCH v5 1/5] powerpc/smp: Enable Asym packing for cores on shared processor
Date: Fri, 15 Dec 2023 10:31:26 +0530 [thread overview]
Message-ID: <87zfyct5y1.fsf@kernel.org> (raw)
In-Reply-To: <20231214180720.310852-2-srikar@linux.vnet.ibm.com>
Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
> If there are shared processor LPARs, underlying Hypervisor can have more
> virtual cores to handle than actual physical cores.
>
> Starting with Power 9, a big core (aka SMT8 core) has 2 nearly
> independent thread groups. On a shared processors LPARs, it helps to
> pack threads to lesser number of cores so that the overall system
> performance and utilization improves. PowerVM schedules at a big core
> level. Hence packing to fewer cores helps.
>
....
> +/*
> + * On shared processor LPARs scheduled on a big core (which has two or more
> + * independent thread groups per core), prefer lower numbered CPUs, so
> + * that workload consolidates to lesser number of cores.
> + */
> +static __ro_after_init DEFINE_STATIC_KEY_FALSE(splpar_asym_pack);
DEFINE_STATIC_KEY_FALSE_RO ?
> +
> /*
> * P9 has a slightly odd architecture where pairs of cores share an L2 cache.
> * This topology makes it *much* cheaper to migrate tasks between adjacent cores
> @@ -1011,9 +1018,20 @@ static int powerpc_smt_flags(void)
> */
-aneesh
next prev parent reply other threads:[~2023-12-15 5:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-14 18:07 [PATCH v5 0/5] powerpc/smp: Topology and shared processor optimizations Srikar Dronamraju
2023-12-14 18:07 ` [PATCH v5 1/5] powerpc/smp: Enable Asym packing for cores on shared processor Srikar Dronamraju
2023-12-15 5:01 ` Aneesh Kumar K.V [this message]
2023-12-14 18:07 ` [PATCH v5 2/5] powerpc/smp: Disable MC domain for " Srikar Dronamraju
2023-12-14 18:07 ` [PATCH v5 3/5] powerpc/smp: Add __ro_after_init attribute Srikar Dronamraju
2023-12-14 18:07 ` [PATCH v5 4/5] powerpc/smp: Avoid asym packing within thread_group of a core Srikar Dronamraju
2023-12-14 18:07 ` [PATCH v5 5/5] powerpc/smp: Dynamically build Powerpc topology Srikar Dronamraju
2023-12-21 10:38 ` [PATCH v5 0/5] powerpc/smp: Topology and shared processor optimizations Michael Ellerman
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