Messages in this thread | | | Subject | Re: [PATCH] arch_topology: Make cluster topology span at least SMT CPUs | From | Yicong Yang <> | Date | Wed, 24 Aug 2022 09:31:24 +0800 |
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On 2022/8/24 1:53, Ionela Voinescu wrote: > 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? >
yes non-cluster means machine has no cluster topology. The PPTT is generated by the qemu according to the cmdline so I didn't really check it. See the demo provided in the commit.
'-smp 48,sockets=2,cores=12,threads=2' builds a mahine with 2 sockets, one socket has 12 cores and each core has 2 threads. If we want to have a cluster machine we build it with '-smp 48,sockets=2,clusters=6,cores=2,threads=2', then we'll have 6 clusters in one socket and 2 cores in each cluster, 2 threads for each core.
Thanks.
> 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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