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Message-ID: <bcd61ebd-d751-57a3-690b-b76c7bd230c5@huawei.com>
Date: Fri, 16 Sep 2022 15:59:34 +0800
From: Yicong Yang <yangyicong@...wei.com>
To: Darren Hart <darren@...amperecomputing.com>
CC: <yangyicong@...ilicon.com>, Sudeep Holla <sudeep.holla@....com>,
Dietmar Eggemann <dietmar.eggemann@....com>,
"Rafael J. Wysocki" <rafael@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"D . Scott Phillips" <scott@...amperecomputing.com>,
Ilkka Koskinen <ilkka@...amperecomputing.com>,
<stable@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
Linux Arm <linux-arm-kernel@...ts.infradead.org>,
Ionela Voinescu <ionela.voinescu@....com>,
Barry Song <21cnbao@...il.com>,
Jonathan Cameron <jonathan.cameron@...wei.com>
Subject: Re: [PATCH v5] topology: make core_mask include at least
cluster_siblings
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,
>
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