... and clarify why this is needed at all right now. It all boils down to false positives. We will try to remove the false positives for !ZONE_DEVICE memory, soon, however, for ZONE_DEVICE memory we won't be able to easily get rid of false positives.
Don't only detect "all holes" but try to shrink using the existing functions we have. Cc: Andrew Morton <[email protected]> Cc: Oscar Salvador <[email protected]> Cc: David Hildenbrand <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Pavel Tatashin <[email protected]> Cc: Dan Williams <[email protected]> Cc: Wei Yang <[email protected]> Signed-off-by: David Hildenbrand <[email protected]> --- mm/memory_hotplug.c | 45 +++++++++++++++++++++++---------------------- 1 file changed, 23 insertions(+), 22 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index d3c34bbeb36d..663853bf97ed 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -411,32 +411,33 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, } } - /* - * The section is not biggest or smallest mem_section in the zone, it - * only creates a hole in the zone. So in this case, we need not - * change the zone. But perhaps, the zone has only hole data. Thus - * it check the zone has only hole or not. - */ - for (pfn = zone->zone_start_pfn; - pfn < zone_end_pfn(zone); pfn += PAGES_PER_SUBSECTION) { - if (unlikely(!pfn_valid(pfn))) - continue; - - if (page_zone(pfn_to_page(pfn)) != zone) - continue; - - /* Skip range to be removed */ - if (pfn >= start_pfn && pfn < end_pfn) - continue; - - /* If we find valid section, we have nothing to do */ + if (!zone->spanned_pages) { zone_span_writeunlock(zone); return; } - /* The zone has no valid section */ - zone->zone_start_pfn = 0; - zone->spanned_pages = 0; + /* + * Due to false positives in previous skrink attempts, it can happen + * that we can shrink the zones further (possibly to zero). Once we + * can reliably detect which PFNs actually belong to a zone + * (especially for ZONE_DEVICE memory where we don't have online + * sections), this can go. + */ + pfn = find_smallest_section_pfn(nid, zone, zone->zone_start_pfn, + zone_end_pfn(zone)); + if (pfn) { + zone->spanned_pages = zone_end_pfn(zone) - pfn; + zone->zone_start_pfn = pfn; + + pfn = find_biggest_section_pfn(nid, zone, zone->zone_start_pfn, + zone_end_pfn(zone)); + if (pfn) + zone->spanned_pages = pfn - zone->zone_start_pfn + 1; + } + if (!pfn) { + zone->zone_start_pfn = 0; + zone->spanned_pages = 0; + } zone_span_writeunlock(zone); } -- 2.21.0
