From: Arve Hjønnevåg <arve@android.com>
Date: Thu, 19 Mar 2009 00:27:31 +0000 (-0700)
Subject: mm: Check if any page in a pageblock is reserved before marking it MIGRATE_RESERVE
X-Git-Tag: firefly_0821_release~11780
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=675bed294c5136b04e283f647e5c73fb897cfd19;p=firefly-linux-kernel-4.4.55.git

mm: Check if any page in a pageblock is reserved before marking it MIGRATE_RESERVE

This fixes a problem where the first pageblock got marked MIGRATE_RESERVE even
though it only had a few free pages. This in turn caused no contiguous memory
to be reserved and frequent kswapd wakeups that emptied the caches to get more
contiguous memory.
---

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 70d43bf00dc6..cfaa29bbc733 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2858,6 +2858,20 @@ static inline unsigned long wait_table_bits(unsigned long size)
 
 #define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1))
 
+/*
+ * Check if a pageblock contains reserved pages
+ */
+static int pageblock_is_reserved(unsigned long start_pfn)
+{
+	unsigned long end_pfn = start_pfn + pageblock_nr_pages;
+	unsigned long pfn;
+
+	for (pfn = start_pfn; pfn < end_pfn; pfn++)
+		if (PageReserved(pfn_to_page(pfn)))
+			return 1;
+	return 0;
+}
+
 /*
  * Mark a number of pageblocks as MIGRATE_RESERVE. The number
  * of blocks reserved is based on min_wmark_pages(zone). The memory within
@@ -2897,7 +2911,7 @@ static void setup_zone_migrate_reserve(struct zone *zone)
 			continue;
 
 		/* Blocks with reserved pages will never free, skip them. */
-		if (PageReserved(page))
+		if (pageblock_is_reserved(pfn))
 			continue;
 
 		block_migratetype = get_pageblock_migratetype(page);