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Subject[PATCH 07/22] Calculate the preferred zone for allocation only once
Date
get_page_from_freelist() can be called multiple times for an allocation.
Part of this calculates the preferred_zone which is the first usable zone
in the zonelist but the zone depends on the GFP flags specified at the
beginning of the allocation call. This patch calculates preferred_zone
once. It's safe to do this because if preferred_zone is NULL at the start
of the call, no amount of direct reclaim or other actions will change the
fact the allocation will fail.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>
---
mm/page_alloc.c | 53 ++++++++++++++++++++++++++++++++---------------------
1 files changed, 32 insertions(+), 21 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b1ae435..e073fa3 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1392,23 +1392,18 @@ static void zlc_mark_zone_full(struct zonelist *zonelist, struct zoneref *z)
*/
static struct page *
get_page_from_freelist(gfp_t gfp_mask, nodemask_t *nodemask, unsigned int order,
- struct zonelist *zonelist, int high_zoneidx, int alloc_flags)
+ struct zonelist *zonelist, int high_zoneidx, int alloc_flags,
+ struct zone *preferred_zone)
{
struct zoneref *z;
struct page *page = NULL;
int classzone_idx;
- struct zone *zone, *preferred_zone;
+ struct zone *zone;
nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */
int zlc_active = 0; /* set if using zonelist_cache */
int did_zlc_setup = 0; /* just call zlc_setup() one time */

- (void)first_zones_zonelist(zonelist, high_zoneidx, nodemask,
- &preferred_zone);
- if (!preferred_zone)
- return NULL;
-
classzone_idx = zone_idx(preferred_zone);
-
VM_BUG_ON(order >= MAX_ORDER);

zonelist_scan:
@@ -1503,7 +1498,7 @@ should_alloc_retry(gfp_t gfp_mask, unsigned int order,
static inline struct page *
__alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
- nodemask_t *nodemask)
+ nodemask_t *nodemask, struct zone *preferred_zone)
{
struct page *page;

@@ -1520,7 +1515,8 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
*/
page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask,
order, zonelist, high_zoneidx,
- ALLOC_WMARK_HIGH|ALLOC_CPUSET);
+ ALLOC_WMARK_HIGH|ALLOC_CPUSET,
+ preferred_zone);
if (page)
goto out;

@@ -1540,7 +1536,8 @@ out:
static inline struct page *
__alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
- nodemask_t *nodemask, int alloc_flags, unsigned long *did_some_progress)
+ nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
+ unsigned long *did_some_progress)
{
struct page *page = NULL;
struct reclaim_state reclaim_state;
@@ -1572,7 +1569,8 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order,

if (likely(*did_some_progress))
page = get_page_from_freelist(gfp_mask, nodemask, order,
- zonelist, high_zoneidx, alloc_flags);
+ zonelist, high_zoneidx,
+ alloc_flags, preferred_zone);
return page;
}

@@ -1592,13 +1590,14 @@ is_allocation_high_priority(struct task_struct *p, gfp_t gfp_mask)
static inline struct page *
__alloc_pages_high_priority(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
- nodemask_t *nodemask)
+ nodemask_t *nodemask, struct zone *preferred_zone)
{
struct page *page;

do {
page = get_page_from_freelist(gfp_mask, nodemask, order,
- zonelist, high_zoneidx, ALLOC_NO_WATERMARKS);
+ zonelist, high_zoneidx, ALLOC_NO_WATERMARKS,
+ preferred_zone);

if (!page && gfp_mask & __GFP_NOFAIL)
congestion_wait(WRITE, HZ/50);
@@ -1621,7 +1620,7 @@ void wake_all_kswapd(unsigned int order, struct zonelist *zonelist,
static inline struct page *
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, enum zone_type high_zoneidx,
- nodemask_t *nodemask)
+ nodemask_t *nodemask, struct zone *preferred_zone)
{
const gfp_t wait = gfp_mask & __GFP_WAIT;
struct page *page = NULL;
@@ -1671,7 +1670,8 @@ restart:
* See also cpuset_zone_allowed() comment in kernel/cpuset.c.
*/
page = get_page_from_freelist(gfp_mask, nodemask, order, zonelist,
- high_zoneidx, alloc_flags);
+ high_zoneidx, alloc_flags,
+ preferred_zone);
if (page)
goto got_pg;

@@ -1681,7 +1681,7 @@ rebalance:
/* Do not dip into emergency reserves if specified */
if (!(gfp_mask & __GFP_NOMEMALLOC)) {
page = __alloc_pages_high_priority(gfp_mask, order,
- zonelist, high_zoneidx, nodemask);
+ zonelist, high_zoneidx, nodemask, preferred_zone);
if (page)
goto got_pg;
}
@@ -1698,7 +1698,8 @@ rebalance:
page = __alloc_pages_direct_reclaim(gfp_mask, order,
zonelist, high_zoneidx,
nodemask,
- alloc_flags, &did_some_progress);
+ alloc_flags, preferred_zone,
+ &did_some_progress);
if (page)
goto got_pg;

@@ -1710,7 +1711,7 @@ rebalance:
if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
page = __alloc_pages_may_oom(gfp_mask, order,
zonelist, high_zoneidx,
- nodemask);
+ nodemask, preferred_zone);
if (page)
goto got_pg;

@@ -1755,6 +1756,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
struct zonelist *zonelist, nodemask_t *nodemask)
{
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
+ struct zone *preferred_zone;
struct page *page;

lockdep_trace_alloc(gfp_mask);
@@ -1772,11 +1774,20 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
if (unlikely(!zonelist->_zonerefs->zone))
return NULL;

+ /* The preferred zone is used for statistics later */
+ (void)first_zones_zonelist(zonelist, high_zoneidx, nodemask,
+ &preferred_zone);
+ if (!preferred_zone)
+ return NULL;
+
+ /* First allocation attempt */
page = get_page_from_freelist(gfp_mask|__GFP_HARDWALL, nodemask, order,
- zonelist, high_zoneidx, ALLOC_WMARK_LOW|ALLOC_CPUSET);
+ zonelist, high_zoneidx, ALLOC_WMARK_LOW|ALLOC_CPUSET,
+ preferred_zone);
if (unlikely(!page))
page = __alloc_pages_slowpath(gfp_mask, order,
- zonelist, high_zoneidx, nodemask);
+ zonelist, high_zoneidx, nodemask,
+ preferred_zone);

return page;
}
--
1.5.6.5


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