On Fri, Jul 14, 2017 at 12:50:04PM +0200, Michal Hocko wrote:
> On Fri 14-07-17 10:48:10, Mel Gorman wrote:
> > On Fri, Jul 14, 2017 at 10:00:00AM +0200, Michal Hocko wrote:
> > > From: Michal Hocko <mho...@suse.com>
> > >
> > > __build_all_zonelists reinitializes each online cpu local node for
> > > CONFIG_HAVE_MEMORYLESS_NODES. This makes sense because previously memory
> > > less nodes could gain some memory during memory hotplug and so the local
> > > node should be changed for CPUs close to such a node. It makes less
> > > sense to do that unconditionally for a newly creaded NUMA node which is
> > > still offline and without any memory.
> > >
> > > Let's also simplify the cpu loop and use for_each_online_cpu instead of
> > > an explicit cpu_online check for all possible cpus.
> > >
> > > Signed-off-by: Michal Hocko <mho...@suse.com>
> > > ---
> > > mm/page_alloc.c | 6 ++----
> > > 1 file changed, 2 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > index 7746824a425d..ebc3311555b1 100644
> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -5096,10 +5096,8 @@ static int __build_all_zonelists(void *data)
> > >
> > > build_zonelists(pgdat);
> > > }
> > > - }
> > >
> > > #ifdef CONFIG_HAVE_MEMORYLESS_NODES
> > > - for_each_possible_cpu(cpu) {
> > > /*
> > > * We now know the "local memory node" for each node--
> > > * i.e., the node of the first zone in the generic zonelist.
> > > @@ -5108,10 +5106,10 @@ static int __build_all_zonelists(void *data)
> > > * secondary cpus' numa_mem as they come on-line. During
> > > * node/memory hotplug, we'll fixup all on-line cpus.
> > > */
> > > - if (cpu_online(cpu))
> > > + for_each_online_cpu(cpu)
> > > set_cpu_numa_mem(cpu,
> > > local_memory_node(cpu_to_node(cpu)));
> > > - }
> > > #endif
> > > + }
> > >
> >
> > This is not as clear a benefit. For each online node, we now go through
> > all online CPUs once per node. There would be some rationale for using
> > for_each_online_cpu.
>
> I am not sure I understand. I am using for_each_online_cpu...
Yes, but within a loop that looks like
for_each_online_node(nid)
...
for_each_online_cpu(cpu)
Or maybe you aren't because we are looking at different baselines. I had
minor fuzz and conflicts applying the series.
--
Mel Gorman
SUSE Labs
