On Fri, Sep 16, 2022 at 03:59:34PM +0800, Yicong Yang wrote: > On 2022/9/16 1:56, Darren Hart wrote: > > On Thu, Sep 15, 2022 at 08:01:18PM +0800, Yicong Yang wrote: > >> Hi Darren, > >> > > > > Hi Yicong, > > > > ... > > > >>> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > >>> index 1d6636ebaac5..5497c5ab7318 100644 > >>> --- a/drivers/base/arch_topology.c > >>> +++ b/drivers/base/arch_topology.c > >>> @@ -667,6 +667,15 @@ const struct cpumask *cpu_coregroup_mask(int cpu) > >>> core_mask = &cpu_topology[cpu].llc_sibling; > >>> } > >>> > >>> + /* > >>> + * For systems with no shared cpu-side LLC but with clusters defined, > >>> + * extend core_mask to cluster_siblings. The sched domain builder will > >>> + * then remove MC as redundant with CLS if SCHED_CLUSTER is enabled. > >>> + */ > >>> + if (IS_ENABLED(CONFIG_SCHED_CLUSTER) && > >>> + cpumask_subset(core_mask, &cpu_topology[cpu].cluster_sibling)) > >>> + core_mask = &cpu_topology[cpu].cluster_sibling; > >>> + > >>> return core_mask; > >>> } > >>> > >> > >> Is this patch still necessary for Ampere after Ionela's patch [1], which > >> will limit the cluster's span within coregroup's span. > > > > Yes, see: > > https://lore.kernel.org/lkml/YshYAyEWhE4z%2FKpB@fedora/ > > > > Both patches work together to accomplish the desired sched domains for the > > Ampere Altra family. > > > > Thanks for the link. From my understanding, on the Altra machine we'll get > the following results: > > with your patch alone: > Scheduler will get a weight of 2 for both CLS and MC level and finally the > MC domain will be squashed. The lowest domain will be CLS. > > with both your patch and Ionela's: > CLS will have a weight of 1 and MC will have a weight of 2. CLS won't be > built and the lowest domain will be MC. > > with Ionela's patch alone: > Both CLS and MC will have a weight of 1, which is incorrect. > > So your patch is still necessary for Amphere Altra. Then we need to limit > MC span to DIE/NODE span, according to the scheduler's definition for > topology level, for the issue below. Maybe something like this: That seems reasonable. What isn't clear to me is why qemu is creating a cluster layer with the description you provide. Why is cluster_siblings being populated? > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 46cbe4471e78..8ebaba576836 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -713,6 +713,9 @@ const struct cpumask *cpu_coregroup_mask(int cpu) > cpumask_subset(core_mask, &cpu_topology[cpu].cluster_sibling)) > core_mask = &cpu_topology[cpu].cluster_sibling; > > + if (cpumask_subset(cpu_cpu_mask(cpu), core_mask)) > + core_mask = cpu_cpu_mask(cpu); > + > return core_mask; > } > > >> > >> I found an issue that the NUMA domains are not built on qemu with: > >> > >> qemu-system-aarch64 \ > >> -kernel ${Image} \ > >> -smp 8 \ > >> -cpu cortex-a72 \ > >> -m 32G \ > >> -object memory-backend-ram,id=node0,size=8G \ > >> -object memory-backend-ram,id=node1,size=8G \ > >> -object memory-backend-ram,id=node2,size=8G \ > >> -object memory-backend-ram,id=node3,size=8G \ > >> -numa node,memdev=node0,cpus=0-1,nodeid=0 \ > >> -numa node,memdev=node1,cpus=2-3,nodeid=1 \ > >> -numa node,memdev=node2,cpus=4-5,nodeid=2 \ > >> -numa node,memdev=node3,cpus=6-7,nodeid=3 \ > >> -numa dist,src=0,dst=1,val=12 \ > >> -numa dist,src=0,dst=2,val=20 \ > >> -numa dist,src=0,dst=3,val=22 \ > >> -numa dist,src=1,dst=2,val=22 \ > >> -numa dist,src=1,dst=3,val=24 \ > >> -numa dist,src=2,dst=3,val=12 \ > >> -machine virt,iommu=smmuv3 \ > >> -net none \ > >> -initrd ${Rootfs} \ > >> -nographic \ > >> -bios QEMU_EFI.fd \ > >> -append "rdinit=/init console=ttyAMA0 earlycon=pl011,0x9000000 sched_verbose loglevel=8" > >> > >> I can see the schedule domain build stops at MC level since we reach all the > >> cpus in the system: > >> > >> [ 2.141316] CPU0 attaching sched-domain(s): > >> [ 2.142558] domain-0: span=0-7 level=MC > >> [ 2.145364] groups: 0:{ span=0 cap=964 }, 1:{ span=1 cap=914 }, 2:{ span=2 cap=921 }, 3:{ span=3 cap=964 }, 4:{ span=4 cap=925 }, 5:{ span=5 cap=964 }, 6:{ span=6 cap=967 }, 7:{ span=7 cap=967 } > >> [ 2.158357] CPU1 attaching sched-domain(s): > >> [ 2.158964] domain-0: span=0-7 level=MC > >> [...] > >> > >> Without this the NUMA domains are built correctly: > >> > > > Without which? My patch, Ionela's patch, or both? > > > > Revert your patch only will have below result, sorry for the ambiguous. Before reverting, > for CPU 0, MC should span 0-1 but with your patch it's extended to 0-7 and the scheduler > domain build will stop at MC level because it has reached all the CPUs. > > >> [ 2.008885] CPU0 attaching sched-domain(s): > >> [ 2.009764] domain-0: span=0-1 level=MC > >> [ 2.012654] groups: 0:{ span=0 cap=962 }, 1:{ span=1 cap=925 } > >> [ 2.016532] domain-1: span=0-3 level=NUMA > >> [ 2.017444] groups: 0:{ span=0-1 cap=1887 }, 2:{ span=2-3 cap=1871 } > >> [ 2.019354] domain-2: span=0-5 level=NUMA > > > > I'm not following this topology - what in the description above should result in > > a domain with span=0-5? > > > > It emulates a 3-hop NUMA machine and the NUMA domains will be built according to the > NUMA distances: > > node 0 1 2 3 > 0: 10 12 20 22 > 1: 12 10 22 24 > 2: 20 22 10 12 > 3: 22 24 12 10 > > So for CPU 0 the NUMA domains will look like: > NUMA domain 0 for local nodes (squashed to MC domain), CPU 0-1 > NUMA domain 1 for nodes within distance 12, CPU 0-3 > NUMA domain 2 for nodes within distance 20, CPU 0-5 > NUMA domain 3 for all the nodes, CPU 0-7 > Right, thanks for the explanation. So the bit that remains unclear to me, is why is cluster_siblings being populated? Which part of your qemu topology description becomes the CLS layer during sched domain cosntruction? -- Darren Hart Ampere Computing / OS and Kernel
