From: Michael Ellerman <mpe@ellerman.id.au>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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 07/10] Powerpc/numa: Detect support for coregroup
Date: Fri, 31 Jul 2020 21:31:13 +1000 [thread overview]
Message-ID: <87r1sr53b2.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20200731091859.GG14603@linux.vnet.ibm.com>
Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
> * Michael Ellerman <mpe@ellerman.id.au> [2020-07-31 17:49:55]:
>
>> Srikar Dronamraju <srikar@linux.vnet.ibm.com> writes:
>> > Add support for grouping cores based on the device-tree classification.
>> > - The last domain in the associativity domains always refers to the
>> > core.
>> > - If primary reference domain happens to be the penultimate domain in
>> > the associativity domains device-tree property, then there are no
>> > coregroups. However if its not a penultimate domain, then there are
>> > coregroups. There can be more than one coregroup. For now we would be
>> > interested in the last or the smallest coregroups.
>>
>> This still doesn't tell me what a coregroup actually represents.
>>
>> I get that it's a grouping of cores, and that the device tree specifies
>> it for us, but grouping based on what?
>
> We have just abstracted the fact that we are creating a sub-group of cores
> within a DIE. We are limiting to one sub-group per core. However this would
> allow the firmware the flexibility to vary the grouping. Once the firmware
> starts using this group, we could add more code to detect the type of
> grouping and adjust the sd domain flags accordingly.
OK. That's good info to have in the change log.
>> I think the answer is we aren't being told by firmware, it's just a
>> grouping based on some opaque performance characteristic and we just
>> have to take that as given.
>>
>
> This is partially true. At this time, we dont have firmwares that can
> exploit this code. Once the firmwares start using this grouping, we could
> add more code to align the grouping to the scheduler topology.
>
>> But please explain that clearly in the change log and the code comments.
>>
>
> Okay, I will do the needful.
Thanks.
cheers
next prev parent reply other threads:[~2020-07-31 11:34 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
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 [this message]
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 07/10] Powerpc/numa: Detect support for coregroup Srikar Dronamraju
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