Mel Gorman wrote:
On (13/12/07 16:37), Andrew Morton didst pronounce:
On Thu, 13 Dec 2007 19:30:00 -0500
Mark Lord <liml@xxxxxx> wrote:
Here's the commit that causes the regression:
...
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -760,7 +760,8 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
struct page *page = __rmqueue(zone, order, migratetype);
if (unlikely(page == NULL))
break;
- list_add_tail(&page->lru, list);
+ list_add(&page->lru, list);
well that looks fishy.
The reasoning behind the change was the first page encountered on the list
by the caller would have a matching migratetype. I failed to take into
account the physical ordering of pages returned. I'm setting up to run some
performance benchmarks of the candidate fix merged into the -mm tree to see
if the search shows up or not. I'm testing against 2.6.25-rc5 but it'll
take a few hours to complete.
..
Thanks, Mel. This is all with CONFIG_SLAB=y, by the way.
Note that it did appear to behave better with CONFIG_SLUB=y when I accidently
used that .config on my 4GB machine here. Physical segments of 4-10 pages
happended much more common than with CONFIG_SLAB=y on my 3GB machine
Slightly "apples and oranges" there, I know, but at least both were x86-32. :)
So I would expect CONFIG_SLAB to be well off with this patch under most (all?)
conditions, but dunno about CONFIG_SLUB.
Cheers
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