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. -- Michal Hocko SUSE Labs
