Re: [PATCH v6 08/10] mm/memory_hotplug: Don't check for "all holes" in shrink_zone_span()

David Hildenbrand
2020-02-04T14:43:10Z

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 :)

This change at least maintains the same result as before (where the
all-holes check would have caught it).

--
Thanks,

David / dhildenb