linux-kernel - [PATCH] mm: call cond_resched() per MAX_ORDER_NR

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Message-ID: <1384800841-314l1f3e-mutt-n-horiguchi@ah.jp.nec.com>
Date:	Mon, 18 Nov 2013 13:54:01 -0500
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Dave Hansen <dave@...1.net>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	dave.jiang@...el.com, akpm@...ux-foundation.org, dhillf@...il.com,
	Mel Gorman <mgorman@...e.de>
Subject: [PATCH] mm: call cond_resched() per MAX_ORDER_NR_PAGES pages copy

In copy_huge_page() we call cond_resched() before every single page copy.
This is an overkill because single page copy is not a heavy operation.
This patch changes this to call cond_resched() per MAX_ORDER_NR_PAGES pages.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
 mm/migrate.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/migrate.c b/mm/migrate.c
index cb5d152b58bc..661ff5f66591 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -454,7 +454,8 @@ static void __copy_gigantic_page(struct page *dst, struct page *src,
 	struct page *src_base = src;
 
 	for (i = 0; i < nr_pages; ) {
-		cond_resched();
+		if (i % MAX_ORDER_NR_PAGES == 0)
+			cond_resched();
 		copy_highpage(dst, src);
 
 		i++;
@@ -483,10 +484,9 @@ static void copy_huge_page(struct page *dst, struct page *src)
 		nr_pages = hpage_nr_pages(src);
 	}
 
-	for (i = 0; i < nr_pages; i++ ) {
-		cond_resched();
+	cond_resched();
+	for (i = 0; i < nr_pages; i++)
 		copy_highpage(dst + i, src + i);
-	}
 }
 
 /*
-- 
1.8.3.1

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