Re: [PATCH v1 2/3] mm/memory_hotplug: don't shuffle complete zone when onlining memory

[Dan Williams]

On Tue, Jun 16, 2020 at 5:51 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
>
> On Tue 16-06-20 13:52:12, David Hildenbrand wrote:
> > Commit e900a918b098 ("mm: shuffle initial free memory to improve
> > memory-side-cache utilization") introduced shuffling of free pages
> > during system boot and whenever we online memory blocks.
> >
> > However, whenever we online memory blocks, all pages that will be
> > exposed to the buddy end up getting freed via __free_one_page(). In the
> > general case, we free these pages in MAX_ORDER - 1 chunks, which
> > corresponds to the shuffle order.
> >
> > Inside __free_one_page(), we will already shuffle the newly onlined pages
> > using "to_tail = shuffle_pick_tail();". Drop explicit zone shuffling on
> > memory hotplug.
> >
> > Note: When hotplugging a DIMM, each memory block (e.g., 128MB .. 2G on
> > x86-64) will get onlined individually, resulting in a shuffle_zone() for
> > every memory block getting onlined.
> >
> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
> > Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Cc: Michal Hocko <mhocko@xxxxxxxx>
> > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>

Nacked-by: Dan Williams <dan.j.williams@xxxxxxxxx>

As explained in another thread this is in active use.