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Subject[PATCH 01/10] vmscan: kill prev_priority completely
Date
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>

Since 2.6.28 zone->prev_priority is unused. Then it can be removed
safely. It reduce stack usage slightly.

Now I have to say that I'm sorry. 2 years ago, I thghout prev_priority
can be integrate again, it's useful. but four (or more) times trying
haven't got good performance number. thus I give up such approach.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
include/linux/mmzone.h | 15 -------------
mm/page_alloc.c | 2 -
mm/vmscan.c | 54 ++---------------------------------------------
mm/vmstat.c | 2 -
4 files changed, 3 insertions(+), 70 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index cf9e458..ad76962 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -339,21 +339,6 @@ struct zone {
atomic_long_t vm_stat[NR_VM_ZONE_STAT_ITEMS];

/*
- * prev_priority holds the scanning priority for this zone. It is
- * defined as the scanning priority at which we achieved our reclaim
- * target at the previous try_to_free_pages() or balance_pgdat()
- * invocation.
- *
- * We use prev_priority as a measure of how much stress page reclaim is
- * under - it drives the swappiness decision: whether to unmap mapped
- * pages.
- *
- * Access to both this field is quite racy even on uniprocessor. But
- * it is expected to average out OK.
- */
- int prev_priority;
-
- /*
* The target ratio of ACTIVE_ANON to INACTIVE_ANON pages on
* this zone's LRU. Maintained by the pageout code.
*/
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d03c946..88513c0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3862,8 +3862,6 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
zone_seqlock_init(zone);
zone->zone_pgdat = pgdat;

- zone->prev_priority = DEF_PRIORITY;
-
zone_pcp_init(zone);
for_each_lru(l) {
INIT_LIST_HEAD(&zone->lru[l].list);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3ff3311..1db19f8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1277,20 +1277,6 @@ done:
}

/*
- * We are about to scan this zone at a certain priority level. If that priority
- * level is smaller (ie: more urgent) than the previous priority, then note
- * that priority level within the zone. This is done so that when the next
- * process comes in to scan this zone, it will immediately start out at this
- * priority level rather than having to build up its own scanning priority.
- * Here, this priority affects only the reclaim-mapped threshold.
- */
-static inline void note_zone_scanning_priority(struct zone *zone, int priority)
-{
- if (priority < zone->prev_priority)
- zone->prev_priority = priority;
-}
-
-/*
* This moves pages from the active list to the inactive list.
*
* We move them the other way if the page is referenced by one or more
@@ -1726,20 +1712,15 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
if (scanning_global_lru(sc)) {
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;
- note_zone_scanning_priority(zone, priority);
-
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
continue; /* Let kswapd poll it */
sc->all_unreclaimable = 0;
- } else {
+ } else
/*
* Ignore cpuset limitation here. We just want to reduce
* # of used pages by us regardless of memory shortage.
*/
sc->all_unreclaimable = 0;
- mem_cgroup_note_reclaim_priority(sc->mem_cgroup,
- priority);
- }

shrink_zone(priority, zone, sc);
}
@@ -1845,17 +1826,11 @@ out:
if (priority < 0)
priority = 0;

- if (scanning_global_lru(sc)) {
- for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
-
+ if (scanning_global_lru(sc))
+ for_each_zone_zonelist(zone, z, zonelist, high_zoneidx)
if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL))
continue;

- zone->prev_priority = priority;
- }
- } else
- mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority);
-
delayacct_freepages_end();

return ret;
@@ -2008,22 +1983,12 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order)
.mem_cgroup = NULL,
.isolate_pages = isolate_pages_global,
};
- /*
- * temp_priority is used to remember the scanning priority at which
- * this zone was successfully refilled to
- * free_pages == high_wmark_pages(zone).
- */
- int temp_priority[MAX_NR_ZONES];
-
loop_again:
total_scanned = 0;
sc.nr_reclaimed = 0;
sc.may_writepage = !laptop_mode;
count_vm_event(PAGEOUTRUN);

- for (i = 0; i < pgdat->nr_zones; i++)
- temp_priority[i] = DEF_PRIORITY;
-
for (priority = DEF_PRIORITY; priority >= 0; priority--) {
int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */
unsigned long lru_pages = 0;
@@ -2091,9 +2056,7 @@ loop_again:
if (zone->all_unreclaimable && priority != DEF_PRIORITY)
continue;

- temp_priority[i] = priority;
sc.nr_scanned = 0;
- note_zone_scanning_priority(zone, priority);

nid = pgdat->node_id;
zid = zone_idx(zone);
@@ -2166,16 +2129,6 @@ loop_again:
break;
}
out:
- /*
- * Note within each zone the priority level at which this zone was
- * brought into a happy state. So that the next thread which scans this
- * zone will start out at that priority level.
- */
- for (i = 0; i < pgdat->nr_zones; i++) {
- struct zone *zone = pgdat->node_zones + i;
-
- zone->prev_priority = temp_priority[i];
- }
if (!all_zones_ok) {
cond_resched();

@@ -2593,7 +2546,6 @@ static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order)
*/
priority = ZONE_RECLAIM_PRIORITY;
do {
- note_zone_scanning_priority(zone, priority);
shrink_zone(priority, zone, &sc);
priority--;
} while (priority >= 0 && sc.nr_reclaimed < nr_pages);
diff --git a/mm/vmstat.c b/mm/vmstat.c
index fa12ea3..2db0a0f 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -761,11 +761,9 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
}
seq_printf(m,
"\n all_unreclaimable: %u"
- "\n prev_priority: %i"
"\n start_pfn: %lu"
"\n inactive_ratio: %u",
zone->all_unreclaimable,
- zone->prev_priority,
zone->zone_start_pfn,
zone->inactive_ratio);
seq_putc(m, '\n');
--
1.6.5


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