linux-kernel - Re: [PATCH v8 0/3] powerpc: Detection and scheduler optimization for POWER9 bigcore

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Message-ID: <133c7bca-5720-81de-7956-b93870a1bab8@intel.com>
Date:   Thu, 20 Sep 2018 11:04:54 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        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>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 0/3] powerpc: Detection and scheduler optimization for
 POWER9 bigcore

On 09/20/2018 10:22 AM, Gautham R. Shenoy wrote:
>  	   -------------------------
> 	   |  	    L1 Cache       |
>        ----------------------------------
>        |L2|     |     |     |      |
>        |  |  0  |  2  |  4  |  6   |Small Core0
>        |C |     |     |     |      |
> Big    |a --------------------------
> Core   |c |     |     |     |      |
>        |h |  1  |  3  |  5  |  7   | Small Core1
>        |e |     |     |     |      |
>        -----------------------------
> 	  |  	    L1 Cache       |
> 	  --------------------------

The scheduler already knows about shared caches.  Could you elaborate on
how this is different from the situation today where we have multiple
cores sharing an L2/L3?

Adding the new sysfs stuff seems like overkill if that's all that you
are trying to do.