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SubjectRe: [PATCH 1/3] mm: page allocator: Update free page counters after pages are placed on the free list
On Fri,  3 Sep 2010 10:08:44 +0100
Mel Gorman <mel@csn.ul.ie> wrote:

> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -588,12 +588,12 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> {
> int migratetype = 0;
> int batch_free = 0;
> + int freed = count;
>
> spin_lock(&zone->lock);
> zone->all_unreclaimable = 0;
> zone->pages_scanned = 0;
>
> - __mod_zone_page_state(zone, NR_FREE_PAGES, count);
> while (count) {
> struct page *page;
> struct list_head *list;
> @@ -621,6 +621,7 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> trace_mm_page_pcpu_drain(page, 0, page_private(page));
> } while (--count && --batch_free && !list_empty(list));
> }
> + __mod_zone_page_state(zone, NR_FREE_PAGES, freed);
> spin_unlock(&zone->lock);
> }
>

nit: this is why it's evil to modify the value of incoming args. It's
nicer to leave them alone and treat them as const across the lifetime
of the callee.

Can I do this?

--- a/mm/page_alloc.c~mm-page-allocator-update-free-page-counters-after-pages-are-placed-on-the-free-list-fix
+++ a/mm/page_alloc.c
@@ -588,13 +588,13 @@ static void free_pcppages_bulk(struct zo
{
int migratetype = 0;
int batch_free = 0;
- int freed = count;
+ int to_free = count;

spin_lock(&zone->lock);
zone->all_unreclaimable = 0;
zone->pages_scanned = 0;

- while (count) {
+ while (to_free) {
struct page *page;
struct list_head *list;

@@ -619,9 +619,9 @@ static void free_pcppages_bulk(struct zo
/* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
__free_one_page(page, zone, 0, page_private(page));
trace_mm_page_pcpu_drain(page, 0, page_private(page));
- } while (--count && --batch_free && !list_empty(list));
+ } while (--to_free && --batch_free && !list_empty(list));
}
- __mod_zone_page_state(zone, NR_FREE_PAGES, freed);
+ __mod_zone_page_state(zone, NR_FREE_PAGES, count);
spin_unlock(&zone->lock);
}

_


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