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From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nathan Lynch <nathanl@linux.ibm.com>,
	Gautham R Shenoy <ego@linux.vnet.ibm.com>,
	Michael Neuling <mikey@neuling.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Jordan Niethe <jniethe5@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Nicholas Piggin <npiggin@gmail.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Oliver O'Halloran <oohall@gmail.com>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH v4 06/10] powerpc/smp: Generalize 2nd sched domain
Date: Fri, 31 Jul 2020 14:59:01 +0530	[thread overview]
Message-ID: <20200731092901.GH14603@linux.vnet.ibm.com> (raw)
In-Reply-To: <875za45dr2.fsf@mpe.ellerman.id.au>

* Michael Ellerman <mpe@ellerman.id.au> [2020-07-31 17:45:37]:

> Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
> > Currently "CACHE" domain happens to be the 2nd sched domain as per
> > powerpc_topology. This domain will collapse if cpumask of l2-cache is
> > same as SMT domain. However we could generalize this domain such that it
> > could mean either be a "CACHE" domain or a "BIGCORE" domain.
> >
> > While setting up the "CACHE" domain, check if shared_cache is already
> > set.
> 
> PeterZ asked for some overview of what you're doing and why, you
> responded to his mail, but I was expecting to see that text incorporated
> here somewhere.
> 

Okay, do you want that as part of the code or documentation dir or the
changelog?

> He also asked for some comments, which I would also like to see.
> 
> 
> I'm also not clear why we want to rename it to "bigcore", that's not a
> commonly understood term, I don't think it's clear to new readers what
> it means.
> 
> Leaving it as the shared cache domain, and having a comment mentioning
> that "bigcores" share a cache, would be clearer I think.
> 

Today, Shared cache is equal to Big Core. However in not too distant future,
Shared cache domain and Big Core may not be the same. For example lets
assume that L2 cache were to Shrink per small core with the firmware
exposing the core as a bigcore. Then with the current design, we have a SMT
== SHARED CACHE, and a DIE. We would not have any domain at the publicised 8
thread level. Keeping the Bigcore as a domain and mapping the shared
cache, (I am resetting the domain name as CACHE if BIGCORE==SHARED_CACHE),
helps us in this scenario.

> cheers
> 

-- 
Thanks and Regards
Srikar Dronamraju

  reply	other threads:[~2020-07-31  9:32 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-27  5:32 [PATCH v4 00/10] Coregroup support on Powerpc Srikar Dronamraju
2020-07-27  5:32 ` [PATCH v4 01/10] powerpc/smp: Fix a warning under !NEED_MULTIPLE_NODES Srikar Dronamraju
2020-07-27  5:32 ` [PATCH v4 02/10] powerpc/smp: Merge Power9 topology with Power topology Srikar Dronamraju
2020-07-27  5:32 ` [PATCH v4 03/10] powerpc/smp: Move powerpc_topology above Srikar Dronamraju
2020-07-27  5:32 ` [PATCH v4 04/10] powerpc/smp: Move topology fixups into a new function Srikar Dronamraju
2020-07-27  5:32 ` [PATCH v4 05/10] powerpc/smp: Dont assume l2-cache to be superset of sibling Srikar Dronamraju
2020-07-27  5:32 ` [PATCH v4 06/10] powerpc/smp: Generalize 2nd sched domain Srikar Dronamraju
2020-07-30  5:55   ` Gautham R Shenoy
2020-07-31  7:45   ` Michael Ellerman
2020-07-31  9:29     ` Srikar Dronamraju [this message]
2020-07-31 12:22       ` Michael Ellerman
2020-07-27  5:32 ` [PATCH v4 07/10] Powerpc/numa: Detect support for coregroup Srikar Dronamraju
2020-07-31  7:49   ` Michael Ellerman
2020-07-31  9:18     ` Srikar Dronamraju
2020-07-31 11:31       ` Michael Ellerman
2020-07-27  5:32 ` [PATCH v4 08/10] powerpc/smp: Allocate cpumask only after searching thread group Srikar Dronamraju
2020-07-31  7:52   ` Michael Ellerman
2020-07-31  9:49     ` Srikar Dronamraju
2020-07-31 12:14       ` Michael Ellerman
2020-07-27  5:32 ` [PATCH v4 09/10] Powerpc/smp: Create coregroup domain Srikar Dronamraju
2020-07-27 18:52   ` Gautham R Shenoy
2020-07-28 15:03   ` Valentin Schneider
2020-07-29  6:13     ` Srikar Dronamraju
2020-07-31  1:05       ` Valentin Schneider
2020-08-03  6:01         ` Srikar Dronamraju
2020-07-31  7:36       ` Gautham R Shenoy
2020-07-27  5:32 ` [PATCH v4 10/10] powerpc/smp: Implement cpu_to_coregroup_id Srikar Dronamraju
2020-07-31  8:02   ` Michael Ellerman
2020-07-31  9:58     ` Srikar Dronamraju
2020-07-31 11:29       ` Michael Ellerman
2020-07-30 17:22 ` [PATCH v4 00/10] Coregroup support on Powerpc Srikar Dronamraju
  -- strict thread matches above, loose matches on Subject: below --
2020-07-27  5:17 Srikar Dronamraju
2020-07-27  5:18 ` [PATCH v4 06/10] powerpc/smp: Generalize 2nd sched domain Srikar Dronamraju

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