linux-kernel - Re: [PATCH 3/3] powerpc/cacheinfo: Print correct cache-sibling map/list for L2 cache

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Date:   Wed, 9 Dec 2020 14:09:21 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Gautham R Shenoy <ego@...ux.vnet.ibm.com>
Cc:     Anton Blanchard <anton@...abs.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michael Neuling <mikey@...ling.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Valentin Schneider <valentin.schneider@....com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] powerpc/cacheinfo: Print correct cache-sibling
 map/list for L2 cache

* Gautham R Shenoy <ego@...ux.vnet.ibm.com> [2020-12-08 23:26:47]:

> > The drawback of this is even if cpus 0,2,4,6 are released L1 cache will not
> > be released. Is this as expected?
> 
> cacheinfo populates the cache->shared_cpu_map on the basis of which
> CPUs share the common device-tree node for a particular cache.  There
> is one l1-cache object in the device-tree for a CPU node corresponding
> to a big-core. That the L1 is further split between the threads of the
> core is shown using ibm,thread-groups.
> 

Yes.

> The ideal thing would be to add a "group_leader" field to "struct
> cache" so that we can create separate cache objects , one per thread
> group. I will take a stab at this in the v2.
> 

I am not saying this needs to be done immediately. We could add a TODO and
get it done later. Your patch is not making it worse. Its just that there is
still something more left to be done.

-- 
Thanks and Regards
Srikar Dronamraju