2012-11-08 06:59:36

by Marek Szyprowski

Subject: [PATCH] mm: skip watermarks check for already isolated blocks in split_free_page()

Since commit 2139cbe627b8 ("cma: fix counting of isolated pages") free
pages in isolated pageblocks are not accounted to NR_FREE_PAGES counters,
so watermarks check is not required if one operates on a free page in
isolated pageblock.

Signed-off-by: Marek Szyprowski <[email protected]>
---
mm/page_alloc.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fd154fe..43ab09f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1394,10 +1394,12 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
zone = page_zone(page);
order = page_order(page);

- /* Obey watermarks as if the page was being allocated */
- watermark = low_wmark_pages(zone) + (1 << order);
- if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
- return 0;
+ if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE) {
+ /* Obey watermarks as if the page was being allocated */
+ watermark = low_wmark_pages(zone) + (1 << order);
+ if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
+ return 0;
+ }

/* Remove page from free list */
list_del(&page->lru);
--
1.7.9.5

2012-11-17 18:20:28

by Francesco Lavra

Subject: Re: [Linaro-mm-sig] [PATCH] mm: skip watermarks check for already isolated blocks in split_free_page()

Hi,

On 11/08/2012 07:59 AM, Marek Szyprowski wrote:
> Since commit 2139cbe627b8 ("cma: fix counting of isolated pages") free
> pages in isolated pageblocks are not accounted to NR_FREE_PAGES counters,
> so watermarks check is not required if one operates on a free page in
> isolated pageblock.
>
> Signed-off-by: Marek Szyprowski <[email protected]>
> ---
> mm/page_alloc.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index fd154fe..43ab09f 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1394,10 +1394,12 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
> zone = page_zone(page);
> order = page_order(page);
>
> - /* Obey watermarks as if the page was being allocated */
> - watermark = low_wmark_pages(zone) + (1 << order);
> - if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
> - return 0;
> + if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE) {

get_pageblock_migratetype(page) is also called later on in this function
and assigned to the mt variable: maybe the assignment should be moved
before (or inside) the above line?

--
Francesco

2012-11-19 14:43:12

by Marek Szyprowski

Subject: [PATCH] mm: cma: skip watermarks check for already isolated blocks in split_free_page() fix

Cleanup and simplify the code which uses page migrate type.

Signed-off-by: Marek Szyprowski <[email protected]>
---
mm/page_alloc.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6b990cb..f05365f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1393,12 +1393,15 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)

zone = page_zone(page);
order = page_order(page);
+ mt = get_pageblock_migratetype(page);

- if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE) {
+ if (mt != MIGRATE_ISOLATE) {
/* Obey watermarks as if the page was being allocated */
watermark = low_wmark_pages(zone) + (1 << order);
if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
return 0;
+
+ __mod_zone_freepage_state(zone, -(1UL << order), mt);
}

/* Remove page from free list */
@@ -1406,10 +1409,6 @@ int capture_free_page(struct page *page, int alloc_order, int migratetype)
zone->free_area[order].nr_free--;
rmv_page_order(page);

- mt = get_pageblock_migratetype(page);
- if (unlikely(mt != MIGRATE_ISOLATE))
- __mod_zone_freepage_state(zone, -(1UL << order), mt);
-
if (alloc_order != order)
expand(zone, page, alloc_order, order,
&zone->free_area[order], migratetype);
--
1.7.9.5