linux-kernel - Re: [PATCH v7 2/2] powerpc: Use cpu_smallcore_sibling

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Message-Id: <20180820180503.GB23117@linux.vnet.ibm.com>
Date:   Mon, 20 Aug 2018 11:05:03 -0700
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Akshay Adiga <akshay.adiga@...ux.vnet.ibm.com>,
        Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>,
        "Oliver O'Halloran" <oohall@...il.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Murilo Opsfelder Araujo <muriloo@...ux.ibm.com>,
        Anton Blanchard <anton@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/2] powerpc: Use cpu_smallcore_sibling_mask at SMT
 level on bigcores

* Gautham R. Shenoy <ego@...ux.vnet.ibm.com> [2018-08-20 11:11:44]:

> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> Each of the SMT4 cores forming a big-core are more or less independent
> units. Thus when multiple tasks are scheduled to run on the fused
> core, we get the best performance when the tasks are spread across the
> pair of SMT4 cores.
> 
> This patch achieves this by setting the SMT level mask to correspond
> to the smallcore sibling mask on big-core systems. This patch also
> ensures that while checked for shared-caches on big-core system, we
> use the smallcore_sibling_mask to compare with the l2_cache_mask.
> This ensure that the CACHE level sched-domain is created, whose groups
> correspond to the threads of the big-core.
> 
> With this patch, the SMT sched-domain with SMT=8,4,2 on big-core
> systems are as follows:


Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>