Messages in this thread |  | | Subject | Re: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span() | From | David Hildenbrand <> | Date | Wed, 5 Feb 2020 14:20:52 +0100 |
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On 05.02.20 13:43, Baoquan He wrote: > On 02/04/20 at 03:42pm, David Hildenbrand wrote: >> On 04.02.20 15:25, Baoquan He wrote: >>> On 10/06/19 at 10:56am, David Hildenbrand wrote: >>>> If we have holes, the holes will automatically get detected and removed >>>> once we remove the next bigger/smaller section. The extra checks can >>>> go. >>>> >>>> Cc: Andrew Morton <akpm@linux-foundation.org> >>>> Cc: Oscar Salvador <osalvador@suse.de> >>>> Cc: Michal Hocko <mhocko@suse.com> >>>> Cc: David Hildenbrand <david@redhat.com> >>>> Cc: Pavel Tatashin <pasha.tatashin@soleen.com> >>>> Cc: Dan Williams <dan.j.williams@intel.com> >>>> Cc: Wei Yang <richardw.yang@linux.intel.com> >>>> Signed-off-by: David Hildenbrand <david@redhat.com> >>>> --- >>>> mm/memory_hotplug.c | 34 +++++++--------------------------- >>>> 1 file changed, 7 insertions(+), 27 deletions(-) >>>> >>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>>> index f294918f7211..8dafa1ba8d9f 100644 >>>> --- a/mm/memory_hotplug.c >>>> +++ b/mm/memory_hotplug.c >>>> @@ -393,6 +393,9 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, >>>> if (pfn) { >>>> zone->zone_start_pfn = pfn; >>>> zone->spanned_pages = zone_end_pfn - pfn; >>>> + } else { >>>> + zone->zone_start_pfn = 0; >>>> + zone->spanned_pages = 0; >>>> } >>>> } else if (zone_end_pfn == end_pfn) { >>>> /* >>>> @@ -405,34 +408,11 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, >>>> start_pfn); >>>> if (pfn) >>>> zone->spanned_pages = pfn - zone_start_pfn + 1; >>>> + else { >>>> + zone->zone_start_pfn = 0; >>>> + zone->spanned_pages = 0; >>> >>> Thinking in which case (zone_start_pfn != start_pfn) and it comes here. >> >> Could only happen in case the zone_start_pfn would have been "out of the >> zone already". If you ask me: unlikely :) > > Yeah, I also think it's unlikely to come here. > > The 'if (zone_start_pfn == start_pfn)' checking also covers the case > (zone_start_pfn == start_pfn && zone_end_pfn == end_pfn). So this > zone_start_pfn/spanned_pages resetting can be removed to avoid > confusion.
At least I would find it more confusing without it (or want a comment explaining why this does not have to be handled and why the !pfn case is not possible).
Anyhow, that patch is already upstream and I don't consider this high priority. Thanks :)
-- Thanks,
David / dhildenb
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