From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Gautham R Shenoy <ego@linux.vnet.ibm.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>,
Oliver OHalloran <oliveroh@au1.ibm.com>,
Michael Neuling <mikey@linux.ibm.com>,
Michael Ellerman <michaele@au1.ibm.com>,
Peter Zijlstra <peterz@infradead.org>,
Jordan Niethe <jniethe5@gmail.com>,
Anton Blanchard <anton@au1.ibm.com>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>, Nick Piggin <npiggin@au1.ibm.com>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
Valentin Schneider <valentin.schneider@arm.com>
Subject: Re: [PATCH v2 06/10] powerpc/smp: Generalize 2nd sched domain
Date: Wed, 22 Jul 2020 13:09:36 +0530 [thread overview]
Message-ID: <20200722073936.GE9290@linux.vnet.ibm.com> (raw)
In-Reply-To: <20200722065640.GE31038@in.ibm.com>
* Gautham R Shenoy <ego@linux.vnet.ibm.com> [2020-07-22 12:26:40]:
> Hello Srikar,
>
> On Tue, Jul 21, 2020 at 05:08:10PM +0530, Srikar Dronamraju wrote:
> > 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.
> > @@ -1339,14 +1345,20 @@ void start_secondary(void *unused)
> > /* Update topology CPU masks */
> > add_cpu_to_masks(cpu);
> >
> > - if (has_big_cores)
> > - sibling_mask = cpu_smallcore_mask;
> > /*
> > * Check for any shared caches. Note that this must be done on a
> > * per-core basis because one core in the pair might be disabled.
> > */
> > - if (!cpumask_equal(cpu_l2_cache_mask(cpu), sibling_mask(cpu)))
> > - shared_caches = true;
> > + if (!shared_caches) {
> > + struct cpumask *(*sibling_mask)(int) = cpu_sibling_mask;
> > + struct cpumask *mask = cpu_l2_cache_mask(cpu);
> > +
> > + if (has_big_cores)
> > + sibling_mask = cpu_smallcore_mask;
> > +
> > + if (cpumask_weight(mask) > cpumask_weight(sibling_mask(cpu)))
> > + shared_caches = true;
>
> At the risk of repeating my comment to the v1 version of the patch, we
> have shared caches only l2_cache_mask(cpu) is a strict superset of
> sibling_mask(cpu).
>
> "cpumask_weight(mask) > cpumask_weight(sibling_mask(cpu))" does not
> capture this.
Why would it not? We are setting shared_caches if and only if l2_cache_mask
is a strict superset of sibling/smallcore mask.
> Could we please use
>
> if (!cpumask_equal(sibling_mask(cpu), mask) &&
> cpumask_subset(sibling_mask(cpu), mask) {
> }
>
Scheduler mandates that two cpumasks for the same CPU would either have to
be equal or one of them has to be a strict superset of the other. If not the
scheduler would mark our domains as broken. That being the case,
cpumask_weight will correctly capture what we are looking for. That said
your condition is also correct but slightly heavier and doesn't provide us
with any more information or correctness.
>
> Otherwise the patch looks good to me.
>
> --
> Thanks and Regards
> gautham.
--
Thanks and Regards
Srikar Dronamraju
next prev parent reply other threads:[~2020-07-22 7:47 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 11:38 [PATCH v2 00/10] Coregroup support on Powerpc Srikar Dronamraju
2020-07-21 11:38 ` [PATCH v2 01/10] powerpc/smp: Cache node for reuse Srikar Dronamraju
2020-07-22 7:41 ` Michael Ellerman
2020-07-22 8:04 ` Srikar Dronamraju
2020-07-21 11:38 ` [PATCH v2 02/10] powerpc/smp: Merge Power9 topology with Power topology Srikar Dronamraju
2020-07-22 5:48 ` Gautham R Shenoy
2020-07-21 11:38 ` [PATCH v2 03/10] powerpc/smp: Move powerpc_topology above Srikar Dronamraju
2020-07-21 11:38 ` [PATCH v2 04/10] powerpc/smp: Enable small core scheduling sooner Srikar Dronamraju
2020-07-22 5:59 ` Gautham R Shenoy
2020-07-22 6:59 ` Srikar Dronamraju
2020-07-21 11:38 ` [PATCH v2 05/10] powerpc/smp: Dont assume l2-cache to be superset of sibling Srikar Dronamraju
2020-07-22 6:21 ` Gautham R Shenoy
2020-07-22 6:57 ` Srikar Dronamraju
2020-07-24 7:10 ` Gautham R Shenoy
2020-07-21 11:38 ` [PATCH v2 06/10] powerpc/smp: Generalize 2nd sched domain Srikar Dronamraju
2020-07-22 6:56 ` Gautham R Shenoy
2020-07-22 7:39 ` Srikar Dronamraju [this message]
2020-07-22 7:46 ` peterz
2020-07-22 8:18 ` Srikar Dronamraju
2020-07-22 8:48 ` Peter Zijlstra
2020-07-22 8:54 ` peterz
2020-07-21 11:38 ` [PATCH v2 07/10] Powerpc/numa: Detect support for coregroup Srikar Dronamraju
2020-07-21 11:38 ` [PATCH v2 08/10] powerpc/smp: Allocate cpumask only after searching thread group Srikar Dronamraju
2020-07-21 11:38 ` [PATCH v2 09/10] Powerpc/smp: Create coregroup domain Srikar Dronamraju
2020-07-22 7:04 ` Gautham R Shenoy
2020-07-22 7:29 ` Srikar Dronamraju
2020-07-21 11:38 ` [PATCH v2 10/10] powerpc/smp: Implement cpu_to_coregroup_id Srikar Dronamraju
2020-07-22 7:06 ` Gautham R Shenoy
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