Re: [PATCH] fix page_alloc for larger I/O segments (improved)

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Andrew Morton wrote:
On Thu, 13 Dec 2007 19:57:29 -0500
James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Thu, 2007-12-13 at 19:46 -0500, Mark Lord wrote:
"Improved version", more similar to the 2.6.23 code:

Fix page allocator to give better chance of larger contiguous segments (again).

Signed-off-by: Mark Lord <mlord@xxxxxxxxx
---

--- old/mm/page_alloc.c	2007-12-13 19:25:15.000000000 -0500
+++ linux-2.6/mm/page_alloc.c	2007-12-13 19:43:07.000000000 -0500
@@ -760,7 +760,7 @@
 		struct page *page = __rmqueue(zone, order, migratetype);
 		if (unlikely(page == NULL))
 			break;
-		list_add(&page->lru, list);
+		list_add_tail(&page->lru, list);
Could we put a big comment above this explaining to the would be vm
tweakers why this has to be a list_add_tail, so we don't end up back in
this position after another two years?


Already done ;)
..

I thought of the comment as I rushed off for dinner.
Thanks, Andrew!

--- a/mm/page_alloc.c~fix-page_alloc-for-larger-i-o-segments-fix
+++ a/mm/page_alloc.c
@@ -847,6 +847,10 @@ static int rmqueue_bulk(struct zone *zon
 		struct page *page = __rmqueue(zone, order, migratetype);
 		if (unlikely(page == NULL))
 			break;
+		/*
+		 * Doing a list_add_tail() here helps us to hand out pages in
+		 * ascending physical-address order.
+		 */
 		list_add_tail(&page->lru, list);
 		set_page_private(page, migratetype);
 	}
_

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