Page allocator: get rid of the list of cold pages

We have repeatedly discussed if the cold pages still have a point. There is
one way to join the two lists: Use a single list and put the cold pages at the
end and the hot pages at the beginning. That way a single list can serve for
both types of allocations.

The discussion of the RFC for this and Mel's measurements indicate that
there may not be too much of a point left to having separate lists for
hot and cold pages (see http://marc.info/?t=119492914200001&r=1&w=2).

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Martin Bligh <mbligh@mbligh.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 4c4522a51a3bfa6667a60d0c593efcf970781e52..8d8d1977736e01c05e48c7c0d3172c30a29bf427 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -113,7 +113,7 @@ struct per_cpu_pages {
 };
 
 struct per_cpu_pageset {
-       struct per_cpu_pages pcp[2];    /* 0: hot.  1: cold */
+       struct per_cpu_pages pcp;
 #ifdef CONFIG_NUMA
        s8 expire;
 #endif

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5c7de8e959fc1485f7253972a922e90d5587ef1f..144c0967e702612df10780fca91b7f587c6be42c 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -901,24 +901,21 @@ static void drain_pages(unsigned int cpu)
 {
        unsigned long flags;
        struct zone *zone;
-       int i;
 
        for_each_zone(zone) {
                struct per_cpu_pageset *pset;
+               struct per_cpu_pages *pcp;
 
                if (!populated_zone(zone))
                        continue;
 
                pset = zone_pcp(zone, cpu);
-               for (i = 0; i < ARRAY_SIZE(pset->pcp); i++) {
-                       struct per_cpu_pages *pcp;
-
-                       pcp = &pset->pcp[i];
-                       local_irq_save(flags);
-                       free_pages_bulk(zone, pcp->count, &pcp->list, 0);
-                       pcp->count = 0;
-                       local_irq_restore(flags);
-               }
+
+               pcp = &pset->pcp;
+               local_irq_save(flags);
+               free_pages_bulk(zone, pcp->count, &pcp->list, 0);
+               pcp->count = 0;
+               local_irq_restore(flags);
        }
 }
 
@@ -993,10 +990,13 @@ static void fastcall free_hot_cold_page(struct page *page, int cold)
        arch_free_page(page, 0);
        kernel_map_pages(page, 1, 0);
 
-       pcp = &zone_pcp(zone, get_cpu())->pcp[cold];
+       pcp = &zone_pcp(zone, get_cpu())->pcp;
        local_irq_save(flags);
        __count_vm_event(PGFREE);
-       list_add(&page->lru, &pcp->list);
+       if (cold)
+               list_add_tail(&page->lru, &pcp->list);
+       else
+               list_add(&page->lru, &pcp->list);
        set_page_private(page, get_pageblock_migratetype(page));
        pcp->count++;
        if (pcp->count >= pcp->high) {
@@ -1054,7 +1054,7 @@ again:
        if (likely(order == 0)) {
                struct per_cpu_pages *pcp;
 
-               pcp = &zone_pcp(zone, cpu)->pcp[cold];
+               pcp = &zone_pcp(zone, cpu)->pcp;
                local_irq_save(flags);
                if (!pcp->count) {
                        pcp->count = rmqueue_bulk(zone, 0,
@@ -1064,9 +1064,15 @@ again:
                }
 
                /* Find a page of the appropriate migrate type */
-               list_for_each_entry(page, &pcp->list, lru)
-                       if (page_private(page) == migratetype)
-                               break;
+               if (cold) {
+                       list_for_each_entry_reverse(page, &pcp->list, lru)
+                               if (page_private(page) == migratetype)
+                                       break;
+               } else {
+                       list_for_each_entry(page, &pcp->list, lru)
+                               if (page_private(page) == migratetype)
+                                       break;
+               }
 
                /* Allocate more to the pcp list if necessary */
                if (unlikely(&page->lru == &pcp->list)) {
@@ -1793,12 +1799,9 @@ void show_free_areas(void)
 
                        pageset = zone_pcp(zone, cpu);
 
-                       printk("CPU %4d: Hot: hi:%5d, btch:%4d usd:%4d   "
-                              "Cold: hi:%5d, btch:%4d usd:%4d\n",
-                              cpu, pageset->pcp[0].high,
-                              pageset->pcp[0].batch, pageset->pcp[0].count,
-                              pageset->pcp[1].high, pageset->pcp[1].batch,
-                              pageset->pcp[1].count);
+                       printk("CPU %4d: hi:%5d, btch:%4d usd:%4d\n",
+                              cpu, pageset->pcp.high,
+                              pageset->pcp.batch, pageset->pcp.count);
                }
        }
 
@@ -2596,17 +2599,11 @@ inline void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
 
        memset(p, 0, sizeof(*p));
 
-       pcp = &p->pcp[0];               /* hot */
+       pcp = &p->pcp;
        pcp->count = 0;
        pcp->high = 6 * batch;
        pcp->batch = max(1UL, 1 * batch);
        INIT_LIST_HEAD(&pcp->list);
-
-       pcp = &p->pcp[1];               /* cold*/
-       pcp->count = 0;
-       pcp->high = 2 * batch;
-       pcp->batch = max(1UL, batch/2);
-       INIT_LIST_HEAD(&pcp->list);
 }
 
 /*
@@ -2619,7 +2616,7 @@ static void setup_pagelist_highmark(struct per_cpu_pageset *p,
 {
        struct per_cpu_pages *pcp;
 
-       pcp = &p->pcp[0]; /* hot list */
+       pcp = &p->pcp;
        pcp->high = high;
        pcp->batch = max(1UL, high/4);
        if ((high/4) > (PAGE_SHIFT * 8))

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 9ffc573ceb6e8539ade001d949d880009aef3208..888668e0b7dbabbdd8b9246845d02edc654d65ad 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -337,7 +337,7 @@ void refresh_cpu_vm_stats(int cpu)
                 * Check if there are pages remaining in this pageset
                 * if not then there is nothing to expire.
                 */
-               if (!p->expire || (!p->pcp[0].count && !p->pcp[1].count))
+               if (!p->expire || !p->pcp.count)
                        continue;
 
                /*
@@ -352,11 +352,8 @@ void refresh_cpu_vm_stats(int cpu)
                if (p->expire)
                        continue;
 
-               if (p->pcp[0].count)
-                       drain_zone_pages(zone, p->pcp + 0);
-
-               if (p->pcp[1].count)
-                       drain_zone_pages(zone, p->pcp + 1);
+               if (p->pcp.count)
+                       drain_zone_pages(zone, &p->pcp);
 #endif
        }
 
@@ -693,20 +690,17 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
                   "\n  pagesets");
        for_each_online_cpu(i) {
                struct per_cpu_pageset *pageset;
-               int j;
 
                pageset = zone_pcp(zone, i);
-               for (j = 0; j < ARRAY_SIZE(pageset->pcp); j++) {
-                       seq_printf(m,
-                                  "\n    cpu: %i pcp: %i"
-                                  "\n              count: %i"
-                                  "\n              high:  %i"
-                                  "\n              batch: %i",
-                                  i, j,
-                                  pageset->pcp[j].count,
-                                  pageset->pcp[j].high,
-                                  pageset->pcp[j].batch);
-                       }
+               seq_printf(m,
+                          "\n    cpu: %i"
+                          "\n              count: %i"
+                          "\n              high:  %i"
+                          "\n              batch: %i",
+                          i,
+                          pageset->pcp.count,
+                          pageset->pcp.high,
+                          pageset->pcp.batch);
 #ifdef CONFIG_SMP
                seq_printf(m, "\n  vm stats threshold: %d",
                                pageset->stat_threshold);