On Fri 25-08-17 18:34:33, Will Deacon wrote:

On Thu, Aug 24, 2017 at 10:32:26AM +0200, Michal Hocko wrote:

quoted

It seems this has slipped through cracks. Let's CC arm64 guys

On Tue 20-06-17 20:43:28, Zhen Lei wrote:

quoted

When I executed numactl -H(which read /sys/devices/system/node/nodeX/cpumap
and display cpumask_of_node for each node), but I got different result on
X86 and arm64. For each numa node, the former only displayed online CPUs,
and the latter displayed all possible CPUs. Unfortunately, both Linux
documentation and numactl manual have not described it clear.

I sent a mail to ask for help, and Michal Hocko [off-list ref] replied
that he preferred to print online cpus because it doesn't really make much
sense to bind anything on offline nodes.

Yes printing offline CPUs is just confusing and more so when the
behavior is not consistent over architectures. I believe that x86
behavior is the more appropriate one because it is more logical to dump
the NUMA topology and use it for affinity setting than adding one
additional step to check the cpu state to achieve the same.

It is true that the online/offline state might change at any time so the
above might be tricky on its own but if we should at least make the
behavior consistent.

quoted

Signed-off-by: Zhen Lei <redacted>

Acked-by: Michal Hocko <mhocko@suse.com>

The concept looks find to me, but shouldn't we use cpumask_var_t and
alloc/free_cpumask_var?

This will be safer but both callers of node_read_cpumap are shallow
stack so I am not sure a stack is a limiting factor here.

Zhen Lei, would you care to update that part please?

-- 
Michal Hocko
SUSE Labs

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