Messages in this thread | | | Date | Tue, 23 Aug 2022 18:53:23 +0100 | From | Ionela Voinescu <> | Subject | Re: [PATCH] arch_topology: Make cluster topology span at least SMT CPUs |
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Hi,
On Tuesday 23 Aug 2022 at 21:05:47 (+0800), Yicong Yang wrote: > On 2022/8/23 16:06, Ionela Voinescu wrote: > > Hi Yicong, > > > > On Tuesday 23 Aug 2022 at 15:30:44 (+0800), Yicong Yang wrote: > >> From: Yicong Yang <yangyicong@hisilicon.com> > >> > >> Currently cpu_clustergroup_mask() will return CPU mask if cluster span > >> more or the same CPUs as cpu_coregroup_mask(). This will result topology > >> borken on non-Cluster SMT machines. > > > > Might be worth adding here:.. "when building with CONFIG_SCHED_CLUSTER=y" > > > > will add this qualifier. thanks. > > >> > > > > I thought I had covered this case, but I think I had considered LLC > > spanning more than one core (tested on TX2 as well). > > > > So you'd only hit this if LLC and cluster level span the same cores (a > > single core in this case, for non-cluster), in the presence of SMT. > > > > Not sure I understand it correctly but in the below case I think the LLC may span > the same core with socket?
Ah, I've jumped to conclusions based on the "non-cluster" mention. Does "non-cluster" just mean that there's no intermediary "cluster" grouping of CPUs between core and LLC? How does the PPTT table look like, by the way?
Thanks, Ionela.
> > > Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com> > > > > Many thanks, > > Ionela. > > > >> Test with: > >> qemu-system-aarch64 -enable-kvm -machine virt \ > >> -net none \ > >> -cpu host \ > >> -bios ./QEMU_EFI.fd \ > >> -m 2G \ > >> -smp 48,sockets=2,cores=12,threads=2 \ > >> -kernel $Image \ > >> -initrd $Rootfs \ > >> -nographic > >> -append "rdinit=init console=ttyAMA0 sched_verbose loglevel=8" > >> > >> We'll get below error: > >> [ 3.084568] BUG: arch topology borken > >> [ 3.084570] the SMT domain not a subset of the CLS domain > >> > >> Since cluster is a level higher than SMT, fix this by making cluster > >> spans at least SMT CPUs. > >> > >> Cc: Sudeep Holla <sudeep.holla@arm.com> > >> Cc: Vincent Guittot <vincent.guittot@linaro.org> > >> Cc: Ionela Voinescu <ionela.voinescu@arm.com> > >> Fixes: bfcc4397435d ("arch_topology: Limit span of cpu_clustergroup_mask()") > >> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> > >> --- > >> drivers/base/arch_topology.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > >> index 0424b59b695e..0056a1273275 100644 > >> --- a/drivers/base/arch_topology.c > >> +++ b/drivers/base/arch_topology.c > >> @@ -724,7 +724,7 @@ const struct cpumask *cpu_clustergroup_mask(int cpu) > >> */ > >> if (cpumask_subset(cpu_coregroup_mask(cpu), > >> &cpu_topology[cpu].cluster_sibling)) > >> - return get_cpu_mask(cpu); > >> + return cpu_smt_mask(cpu); > >> > >> return &cpu_topology[cpu].cluster_sibling; > >> } > >> -- > >> 2.24.0 > >> > > > > . > >
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