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Subject[PATCH] mm,cma: remove pfn_range_valid_contig
The function pfn_range_valid_contig checks whether all memory in the
target area is free. This causes unnecessary CMA failures, since
alloc_contig_range will migrate movable memory out of a target range,
and has its own sanity check early on in has_unmovable_pages, which
is called from start_isolate_page_range & set_migrate_type_isolate.

Relying on that has_unmovable_pages call simplifies the CMA code and
results in an increased success rate of CMA allocations.

Signed-off-by: Rik van Riel <riel@surriel.com>
---
mm/page_alloc.c | 47 +++--------------------------------------------
1 file changed, 3 insertions(+), 44 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0fb3c1719625..75e84907d8c6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8539,32 +8539,6 @@ static int __alloc_contig_pages(unsigned long start_pfn,
gfp_mask);
}

-static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn,
- unsigned long nr_pages)
-{
- unsigned long i, end_pfn = start_pfn + nr_pages;
- struct page *page;
-
- for (i = start_pfn; i < end_pfn; i++) {
- page = pfn_to_online_page(i);
- if (!page)
- return false;
-
- if (page_zone(page) != z)
- return false;
-
- if (PageReserved(page))
- return false;
-
- if (page_count(page) > 0)
- return false;
-
- if (PageHuge(page))
- return false;
- }
- return true;
-}
-
static bool zone_spans_last_pfn(const struct zone *zone,
unsigned long start_pfn, unsigned long nr_pages)
{
@@ -8605,28 +8579,13 @@ struct page *alloc_contig_pages(unsigned long nr_pages, gfp_t gfp_mask,
zonelist = node_zonelist(nid, gfp_mask);
for_each_zone_zonelist_nodemask(zone, z, zonelist,
gfp_zone(gfp_mask), nodemask) {
- spin_lock_irqsave(&zone->lock, flags);
-
pfn = ALIGN(zone->zone_start_pfn, nr_pages);
while (zone_spans_last_pfn(zone, pfn, nr_pages)) {
- if (pfn_range_valid_contig(zone, pfn, nr_pages)) {
- /*
- * We release the zone lock here because
- * alloc_contig_range() will also lock the zone
- * at some point. If there's an allocation
- * spinning on this lock, it may win the race
- * and cause alloc_contig_range() to fail...
- */
- spin_unlock_irqrestore(&zone->lock, flags);
- ret = __alloc_contig_pages(pfn, nr_pages,
- gfp_mask);
- if (!ret)
- return pfn_to_page(pfn);
- spin_lock_irqsave(&zone->lock, flags);
- }
+ ret = __alloc_contig_pages(pfn, nr_pages, gfp_mask);
+ if (!ret)
+ return pfn_to_page(pfn);
pfn += nr_pages;
}
- spin_unlock_irqrestore(&zone->lock, flags);
}
return NULL;
}
--
2.24.1
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