Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx> writes:
>> >>
>> >> if (lr_ratio >= NUMA_PERIOD_THRESHOLD)
>> >> slow down scanning
>> >> else if (sp_ratio >= NUMA_PERIOD_THRESHOLD) {
>> >> if (NUMA_PERIOD_SLOTS - lr_ratio >= NUMA_PERIOD_THRESHOLD)
>> >> speed up scanning
>>
>> Thought about this again. For example, a multi-threads workload runs on
>> a 4-sockets machine, and most memory accesses are shared. The optimal
>> situation will be pseudo-interleaving, that is, spreading memory
>> accesses evenly among 4 NUMA nodes. Where "share" >> "private", and
>> "remote" > "local". And we should slow down scanning to reduce the
>> overhead.
>>
>> What do you think about this?
>
> If all 4 nodes have equal access, then all 4 nodes will be active nodes.
>
> From task_numa_fault()
>
> if (!priv && !local && ng && ng->active_nodes > 1 &&
> numa_is_active_node(cpu_node, ng) &&
> numa_is_active_node(mem_node, ng))
> local = 1;
>
> Hence all accesses will be accounted as local. Hence scanning would slow
> down.
Yes. You are right! Thanks a lot!
There may be another case. For example, a workload with 9 threads runs
on a 2-sockets machine, and most memory accesses are shared. 7 threads
runs on the node 0 and 2 threads runs on the node 1 based on CPU load
balancing. Then the 2 threads on the node 1 will have "share" >>
"private" and "remote" >> "local". But it doesn't help to speed up
scanning.
Best Regards,
Huang, Ying
