On 2019/9/17 17:36, Michal Hocko wrote: > On Tue 17-09-19 14:20:11, Yunsheng Lin wrote: >> On 2019/9/17 13:28, Michael Ellerman wrote: >>> Yunsheng Lin <linyunsheng@xxxxxxxxxx> writes: > [...] >>>> But we cannot really copy the page allocator logic. Simply because the >>>> page allocator doesn't enforce the near node affinity. It just picks it >>>> up as a preferred node but then it is free to fallback to any other numa >>>> node. This is not the case here and node_to_cpumask_map will only restrict >>>> to the particular node's cpus which would have really non deterministic >>>> behavior depending on where the code is executed. So in fact we really >>>> want to return cpu_online_mask for NUMA_NO_NODE. >>>> >>>> Some arches were already NUMA_NO_NODE aware, but they return cpu_all_mask, >>>> which should be identical with cpu_online_mask when those arches do not >>>> support cpu hotplug, this patch also changes them to return cpu_online_mask >>>> in order to be consistent and use NUMA_NO_NODE instead of "-1". >>> >>> Except some of those arches *do* support CPU hotplug, powerpc and sparc >>> at least. So switching from cpu_all_mask to cpu_online_mask is a >>> meaningful change. >> >> Yes, thanks for pointing out. >> >>> >>> That doesn't mean it's wrong, but you need to explain why it's the right >>> change. >> >> How about adding the below to the commit log: >> Even if some of the arches do support CPU hotplug, it does not make sense >> to return the cpu that has been hotplugged. >> >> Any suggestion? > > Again, for the third time, I believe. Make it a separate patch please. > There is absolutely no reason to conflate those two things. Ok, thanks. Will make the cpu_all_mask -> cpu_online_mask change a separate patch. Also, do you think it is better to resend this as individual patches for each arch or have all these changes in a single patch? I am not sure which is the common practice for a multi-arches changes like this. >
