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mm: modify pgdat_balanced() so that it also handles order-0 

Teach pgdat_balanced() about order-0 allocations so that we can simplify
code in a few places in vmstat.c.

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Zlatko Calusic <zlatko.calusic@iskon.hr>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Zlatko Calusic 2012-12-23 15:12:54 +01:00 committed by Linus Torvalds
parent 9c016d6109
commit 4ae0a48b5e
1 changed files with 45 additions and 60 deletions
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105
mm/vmscan.c
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@ -2452,12 +2452,16 @@ static bool zone_balanced(struct zone *zone, int order,
}
/*
* pgdat_balanced is used when checking if a node is balanced for high-order
* allocations. Only zones that meet watermarks and are in a zone allowed
* by the callers classzone_idx are added to balanced_pages. The total of
* balanced pages must be at least 25% of the zones allowed by classzone_idx
* for the node to be considered balanced. Forcing all zones to be balanced
* for high orders can cause excessive reclaim when there are imbalanced zones.
* pgdat_balanced() is used when checking if a node is balanced.
*
* For order-0, all zones must be balanced!
*
* For high-order allocations only zones that meet watermarks and are in a
* zone allowed by the callers classzone_idx are added to balanced_pages. The
* total of balanced pages must be at least 25% of the zones allowed by
* classzone_idx for the node to be considered balanced. Forcing all zones to
* be balanced for high orders can cause excessive reclaim when there are
* imbalanced zones.
* The choice of 25% is due to
* o a 16M DMA zone that is balanced will not balance a zone on any
* reasonable sized machine
@ -2467,17 +2471,43 @@ static bool zone_balanced(struct zone *zone, int order,
* Similarly, on x86-64 the Normal zone would need to be at least 1G
* to balance a node on its own. These seemed like reasonable ratios.
*/
static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
int classzone_idx)
static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx)
{
unsigned long present_pages = 0;
unsigned long balanced_pages = 0;
int i;
for (i = 0; i <= classzone_idx; i++)
present_pages += pgdat->node_zones[i].present_pages;
/* Check the watermark levels */
for (i = 0; i <= classzone_idx; i++) {
struct zone *zone = pgdat->node_zones + i;
/* A special case here: if zone has no page, we think it's balanced */
return balanced_pages >= (present_pages >> 2);
if (!populated_zone(zone))
continue;
present_pages += zone->present_pages;
/*
* A special case here:
*
* balance_pgdat() skips over all_unreclaimable after
* DEF_PRIORITY. Effectively, it considers them balanced so
* they must be considered balanced here as well!
*/
if (zone->all_unreclaimable) {
balanced_pages += zone->present_pages;
continue;
}
if (zone_balanced(zone, order, 0, i))
balanced_pages += zone->present_pages;
else if (!order)
return false;
}
if (order)
return balanced_pages >= (present_pages >> 2);
else
return true;
}
/*
@ -2489,10 +2519,6 @@ static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages,
static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
int classzone_idx)
{
int i;
unsigned long balanced = 0;
bool all_zones_ok = true;
/* If a direct reclaimer woke kswapd within HZ/10, it's premature */
if (remaining)
return false;
@ -2511,39 +2537,7 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
return false;
}
/* Check the watermark levels */
for (i = 0; i <= classzone_idx; i++) {
struct zone *zone = pgdat->node_zones + i;
if (!populated_zone(zone))
continue;
/*
* balance_pgdat() skips over all_unreclaimable after
* DEF_PRIORITY. Effectively, it considers them balanced so
* they must be considered balanced here as well if kswapd
* is to sleep
*/
if (zone->all_unreclaimable) {
balanced += zone->present_pages;
continue;
}
if (!zone_balanced(zone, order, 0, i))
all_zones_ok = false;
else
balanced += zone->present_pages;
}
/*
* For high-order requests, the balanced zones must contain at least
* 25% of the nodes pages for kswapd to sleep. For order-0, all zones
* must be balanced
*/
if (order)
return pgdat_balanced(pgdat, balanced, classzone_idx);
else
return all_zones_ok;
return pgdat_balanced(pgdat, order, classzone_idx);
}
/*
@ -2571,7 +2565,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order,
int *classzone_idx)
{
struct zone *unbalanced_zone;
unsigned long balanced;
int i;
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
unsigned long total_scanned;
@ -2605,7 +2598,6 @@ loop_again:
int has_under_min_watermark_zone = 0;
unbalanced_zone = NULL;
balanced = 0;
/*
* Scan in the highmem->dma direction for the highest
@ -2761,8 +2753,6 @@ loop_again:
* speculatively avoid congestion waits
*/
zone_clear_flag(zone, ZONE_CONGESTED);
if (i <= *classzone_idx)
balanced += zone->present_pages;
}
}
@ -2776,7 +2766,7 @@ loop_again:
pfmemalloc_watermark_ok(pgdat))
wake_up(&pgdat->pfmemalloc_wait);
if (!unbalanced_zone || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))
if (pgdat_balanced(pgdat, order, *classzone_idx))
break; /* kswapd: all done */
/*
* OK, kswapd is getting into trouble. Take a nap, then take
@ -2800,12 +2790,7 @@ loop_again:
} while (--sc.priority >= 0);
out:
/*
* order-0: All zones must meet high watermark for a balanced node
* high-order: Balanced zones must make up at least 25% of the node
* for the node to be balanced
*/
if (unbalanced_zone && (!order || !pgdat_balanced(pgdat, balanced, *classzone_idx))) {
if (!pgdat_balanced(pgdat, order, *classzone_idx)) {
cond_resched();
try_to_freeze();