From: Gautham R Shenoy <ego@linux.vnet.ibm.com>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Nathan Lynch <nathanl@linux.ibm.com>,
Gautham R Shenoy <ego@linux.vnet.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 12:26:40 +0530 [thread overview]
Message-ID: <20200722065640.GE31038@in.ibm.com> (raw)
In-Reply-To: <20200721113814.32284-7-srikar@linux.vnet.ibm.com>
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.
>
> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
> Cc: LKML <linux-kernel@vger.kernel.org>
> Cc: Michael Ellerman <michaele@au1.ibm.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Valentin Schneider <valentin.schneider@arm.com>
> Cc: Nick Piggin <npiggin@au1.ibm.com>
> Cc: Oliver OHalloran <oliveroh@au1.ibm.com>
> Cc: Nathan Lynch <nathanl@linux.ibm.com>
> Cc: Michael Neuling <mikey@linux.ibm.com>
> Cc: Anton Blanchard <anton@au1.ibm.com>
> Cc: Gautham R Shenoy <ego@linux.vnet.ibm.com>
> Cc: Vaidyanathan Srinivasan <svaidy@linux.ibm.com>
> Cc: Jordan Niethe <jniethe5@gmail.com>
> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---
> Changelog v1 -> v2:
> powerpc/smp: Generalize 2nd sched domain
> Moved shared_cache topology fixup to fixup_topology (Gautham)
>
Just one comment below.
> arch/powerpc/kernel/smp.c | 49 ++++++++++++++++++++++++++++-----------
> 1 file changed, 35 insertions(+), 14 deletions(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 57468877499a..933ebdf97432 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -85,6 +85,14 @@ EXPORT_PER_CPU_SYMBOL(cpu_l2_cache_map);
> EXPORT_PER_CPU_SYMBOL(cpu_core_map);
> EXPORT_SYMBOL_GPL(has_big_cores);
>
> +enum {
> +#ifdef CONFIG_SCHED_SMT
> + smt_idx,
> +#endif
> + bigcore_idx,
> + die_idx,
> +};
> +
[..snip..]
> @@ -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.
Could we please use
if (!cpumask_equal(sibling_mask(cpu), mask) &&
cpumask_subset(sibling_mask(cpu), mask) {
}
?
> + }
>
> set_numa_node(numa_cpu_lookup_table[cpu]);
> set_numa_mem(local_memory_node(numa_cpu_lookup_table[cpu]));
> @@ -1374,10 +1386,19 @@ int setup_profiling_timer(unsigned int multiplier)
>
> static void fixup_topology(void)
> {
> + if (shared_caches) {
> + pr_info("Using shared cache scheduler topology\n");
> + powerpc_topology[bigcore_idx].mask = shared_cache_mask;
> +#ifdef CONFIG_SCHED_DEBUG
> + powerpc_topology[bigcore_idx].name = "CACHE";
> +#endif
> + powerpc_topology[bigcore_idx].sd_flags = powerpc_shared_cache_flags;
> + }
> +
> #ifdef CONFIG_SCHED_SMT
> if (has_big_cores) {
> pr_info("Big cores detected but using small core scheduling\n");
> - powerpc_topology[0].mask = smallcore_smt_mask;
> + powerpc_topology[smt_idx].mask = smallcore_smt_mask;
> }
> #endif
Otherwise the patch looks good to me.
--
Thanks and Regards
gautham.
next prev parent reply other threads:[~2020-07-22 6:59 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 [this message]
2020-07-22 7:39 ` Srikar Dronamraju
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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