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: 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 Thanks. > >> [ 2.019983] groups: 0:{ span=0-3 cap=3758 }, 4:{ span=4-5 cap=1935 } >> [ 2.021527] domain-3: span=0-7 level=NUMA >> [ 2.022516] groups: 0:{ span=0-5 mask=0-1 cap=5693 }, 6:{ span=4-7 mask=6-7 cap=3978 } >> [...] >> >> Hope to see your comments since I have no Ampere machine and I don't know >> how to emulate its topology on qemu. >> >> [1] bfcc4397435d ("arch_topology: Limit span of cpu_clustergroup_mask()") >> >> Thanks, >> Yicong > > Thanks, >
