Messages in this thread Patch in this message | | | Date | Mon, 14 Mar 2022 17:35:05 +0100 | Subject | Re: [PATCH v3] topology: make core_mask include at least cluster_siblings | From | Dietmar Eggemann <> |
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On 09/03/2022 19:26, Darren Hart wrote: > On Wed, Mar 09, 2022 at 01:50:07PM +0100, Dietmar Eggemann wrote: >> On 08/03/2022 18:49, Darren Hart wrote: >>> On Tue, Mar 08, 2022 at 05:03:07PM +0100, Dietmar Eggemann wrote: >>>> On 08/03/2022 12:04, Vincent Guittot wrote: >>>>> On Tue, 8 Mar 2022 at 11:30, Will Deacon <will@kernel.org> wrote:
[...]
>>>> I do not have any better idea than this tweak here either in case the >>>> platform can't provide a cleaner setup. >>> >>> I'd argue The platform is describing itself accurately in ACPI PPTT >>> terms. The topology doesn't fit nicely within the kernel abstractions >>> today. This is an area where I hope to continue to improve things going >>> forward. >> >> I see. And I assume lying about SCU/LLC boundaries in ACPI is not an >> option since it messes up /sys/devices/system/cpu/cpu0/cache/index*/. >> >> [...] > > I'm not aware of a way to accurately describe the SCU topology in the PPTT, and > the risk we run with lying about LLC topology is that lie has to be comprehended > by all OSes and not conflict with other lies people may ask for. In general, I > think it is preferable and more maintainable to describe the topology as > accurately and honestly as we can within the existing platform mechanisms (PPTT, > HMAT, etc) and work on the higher level abstractions to accommodate a broader > set of topologies as they emerge (as well as working to more fully describe the > topology with new platform level mechanisms as needed). > > As I mentioned, I intend to continue looking in to how to improve the current > abstractions. For now, it sounds like we have agreement that this patch can be > merged to address the BUG?
What about swapping the CLS and MC cpumasks for such a machine? This would avoid that the task scheduler has to deal with a system which has CLS but no MC. We essentially promote the CLS cpumask up to MC in this case.
cat /sys/kernel/debug/sched/domains/cpu0/domain*/name MC ^^ DIE NUMA
cat /sys/kernel/debug/sched/domains/cpu0# cat domain*/flags SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SHARE_PKG_RESOURCES SD_PREFER_SIBLING ^^^^^^^^^^^^^^^^^^^^^^ SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_PREFER_SIBLING SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_SERIALIZE SD_OVERLAP SD_NUMA
Only very lightly tested on Altra and Juno-r0 (DT).
--->8---
From 54bef59e7f50fa41b7ae39190fd71af57209c27d Mon Sep 17 00:00:00 2001 From: Dietmar Eggemann <dietmar.eggemann@arm.com> Date: Mon, 14 Mar 2022 15:08:23 +0000 Subject: [PATCH] arch_topology: Swap MC & CLS SD mask if MC weight==1 & subset(MC,CLS)
This avoids the issue of having a system with a CLS SD but no MC SD. CLS should be sub-SD of MC.
The cpumask under /sys/devices/system/cpu/cpu*/cache/index* and /sys/devices/system/cpu/cpu*/topology are not changed by this.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> --- drivers/base/arch_topology.c | 30 ++++++++++++++++++++++++++++-- 1 file changed, 28 insertions(+), 2 deletions(-)
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 976154140f0b..9af90a5625c7 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -614,7 +614,7 @@ static int __init parse_dt_topology(void) struct cpu_topology cpu_topology[NR_CPUS]; EXPORT_SYMBOL_GPL(cpu_topology); -const struct cpumask *cpu_coregroup_mask(int cpu) +const struct cpumask *_cpu_coregroup_mask(int cpu) { const cpumask_t *core_mask = cpumask_of_node(cpu_to_node(cpu)); @@ -631,11 +631,37 @@ const struct cpumask *cpu_coregroup_mask(int cpu) return core_mask; } -const struct cpumask *cpu_clustergroup_mask(int cpu) +const struct cpumask *_cpu_clustergroup_mask(int cpu) { return &cpu_topology[cpu].cluster_sibling; } +static int +swap_masks(const cpumask_t *core_mask, const cpumask_t *cluster_mask) +{ + if (cpumask_weight(core_mask) == 1 && + cpumask_subset(core_mask, cluster_mask)) + return 1; + + return 0; +} + +const struct cpumask *cpu_coregroup_mask(int cpu) +{ + const cpumask_t *cluster_mask = _cpu_clustergroup_mask(cpu); + const cpumask_t *core_mask = _cpu_coregroup_mask(cpu); + + return swap_masks(core_mask, cluster_mask) ? cluster_mask : core_mask; +} + +const struct cpumask *cpu_clustergroup_mask(int cpu) +{ + const cpumask_t *cluster_mask = _cpu_clustergroup_mask(cpu); + const cpumask_t *core_mask = _cpu_coregroup_mask(cpu); + + return swap_masks(core_mask, cluster_mask) ? core_mask : cluster_mask; +} + void update_siblings_masks(unsigned int cpuid) { struct cpu_topology *cpu_topo, *cpuid_topo = &cpu_topology[cpuid]; -- 2.25.1
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