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Subject[patch 9/14] mm: page_state opt
9/14

--
SUSE Labs, Novell Inc.

Optimise page_state manipulations by introducing a direct accessor
to page_state fields without disabling interrupts, in which case
the callers must provide their own locking (either disable interrupts
or not update from interrupt context).

Index: linux-2.6/include/linux/page-flags.h
===================================================================
--- linux-2.6.orig/include/linux/page-flags.h
+++ linux-2.6/include/linux/page-flags.h
@@ -138,6 +138,7 @@ extern void get_page_state_node(struct p
extern void get_full_page_state(struct page_state *ret);
extern unsigned long __read_page_state(unsigned long offset);
extern void __mod_page_state(unsigned long offset, unsigned long delta);
+extern unsigned long *__page_state(unsigned long offset);

#define read_page_state(member) \
__read_page_state(offsetof(struct page_state, member))
@@ -150,16 +151,26 @@ extern void __mod_page_state(unsigned lo
#define add_page_state(member,delta) mod_page_state(member, (delta))
#define sub_page_state(member,delta) mod_page_state(member, 0UL - (delta))

-#define mod_page_state_zone(zone, member, delta) \
- do { \
- unsigned offset; \
- if (is_highmem(zone)) \
- offset = offsetof(struct page_state, member##_high); \
- else if (is_normal(zone)) \
- offset = offsetof(struct page_state, member##_normal); \
- else \
- offset = offsetof(struct page_state, member##_dma); \
- __mod_page_state(offset, (delta)); \
+#define page_state(member) (*__page_state(offsetof(struct page_state, member)))
+
+#define state_zone_offset(zone, member) \
+({ \
+ unsigned offset; \
+ if (is_highmem(zone)) \
+ offset = offsetof(struct page_state, member##_high); \
+ else if (is_normal(zone)) \
+ offset = offsetof(struct page_state, member##_normal); \
+ else \
+ offset = offsetof(struct page_state, member##_dma); \
+ offset; \
+})
+
+#define page_state_zone(zone, member) \
+ (*__page_state(state_zone_offset(zone, member)))
+
+#define mod_page_state_zone(zone, member, delta) \
+ do { \
+ __mod_page_state(state_zone_offset(zone, member), (delta)); \
} while (0)

/*
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -400,8 +400,6 @@ void __free_pages_ok(struct page *page,

arch_free_page(page, order);

- mod_page_state(pgfree, 1 << order);
-
#ifndef CONFIG_MMU
if (order > 0)
for (i = 1 ; i < (1 << order) ; ++i)
@@ -413,6 +411,7 @@ void __free_pages_ok(struct page *page,
list_add(&page->lru, &list);
kernel_map_pages(page, 1<<order, 0);
local_irq_save(flags);
+ page_state(pgfree) += 1 << order;
free_pages_bulk(page_zone(page), 1, &list, order);
local_irq_restore(flags);
}
@@ -662,12 +661,12 @@ static void fastcall free_hot_cold_page(
arch_free_page(page, 0);

kernel_map_pages(page, 1, 0);
- inc_page_state(pgfree);
if (PageAnon(page))
page->mapping = NULL;
free_pages_check(page);
pcp = &zone_pcp(zone, get_cpu())->pcp[cold];
local_irq_save(flags);
+ page_state(pgfree)++;
list_add(&page->lru, &pcp->list);
pcp->count++;
if (pcp->count >= pcp->high)
@@ -704,42 +703,50 @@ static struct page *
buffered_rmqueue(struct zone *zone, int order, gfp_t gfp_flags)
{
unsigned long flags;
- struct page *page = NULL;
+ struct page *page;
int cold = !!(gfp_flags & __GFP_COLD);
+ int cpu = get_cpu();

if (order == 0) {
struct per_cpu_pages *pcp;

- pcp = &zone_pcp(zone, get_cpu())->pcp[cold];
+ pcp = &zone_pcp(zone, cpu)->pcp[cold];
local_irq_save(flags);
- if (!pcp->count)
+ if (!pcp->count) {
pcp->count += rmqueue_bulk(zone, 0,
pcp->batch, &pcp->list);
- if (likely(pcp->count)) {
- page = list_entry(pcp->list.next, struct page, lru);
- list_del(&page->lru);
- pcp->count--;
+ if (unlikely(!pcp->count))
+ goto failed;
}
- local_irq_restore(flags);
- put_cpu();
+ page = list_entry(pcp->list.next, struct page, lru);
+ list_del(&page->lru);
+ pcp->count--;
} else {
spin_lock_irqsave(&zone->lock, flags);
page = __rmqueue(zone, order);
- spin_unlock_irqrestore(&zone->lock, flags);
+ spin_unlock(&zone->lock);
+ if (!page)
+ goto failed;
}

- if (page != NULL) {
- BUG_ON(bad_range(zone, page));
- mod_page_state_zone(zone, pgalloc, 1 << order);
- prep_new_page(page, order);
+ page_state_zone(zone, pgalloc) += 1 << order;
+ local_irq_restore(flags);
+ put_cpu();

- if (gfp_flags & __GFP_ZERO)
- prep_zero_page(page, order, gfp_flags);
+ BUG_ON(bad_range(zone, page));
+ prep_new_page(page, order);

- if (order && (gfp_flags & __GFP_COMP))
- prep_compound_page(page, order);
- }
+ if (gfp_flags & __GFP_ZERO)
+ prep_zero_page(page, order, gfp_flags);
+
+ if (order && (gfp_flags & __GFP_COMP))
+ prep_compound_page(page, order);
return page;
+
+failed:
+ local_irq_restore(flags);
+ put_cpu();
+ return NULL;
}

/*
@@ -1215,6 +1222,15 @@ unsigned long __read_page_state(unsigned
return ret;
}

+unsigned long *__page_state(unsigned long offset)
+{
+ void* ptr;
+ ptr = &__get_cpu_var(page_states);
+ return (unsigned long*)(ptr + offset);
+}
+
+EXPORT_SYMBOL(__page_state);
+
void __mod_page_state(unsigned long offset, unsigned long delta)
{
unsigned long flags;
Index: linux-2.6/mm/vmscan.c
===================================================================
--- linux-2.6.orig/mm/vmscan.c
+++ linux-2.6/mm/vmscan.c
@@ -641,17 +641,18 @@ static void shrink_cache(struct zone *zo
goto done;

max_scan -= nr_scan;
- if (current_is_kswapd())
- mod_page_state_zone(zone, pgscan_kswapd, nr_scan);
- else
- mod_page_state_zone(zone, pgscan_direct, nr_scan);
nr_freed = shrink_list(&page_list, sc);
- if (current_is_kswapd())
- mod_page_state(kswapd_steal, nr_freed);
- mod_page_state_zone(zone, pgsteal, nr_freed);
sc->nr_to_reclaim -= nr_freed;

- spin_lock_irq(&zone->lru_lock);
+ local_irq_disable();
+ if (current_is_kswapd()) {
+ page_state_zone(zone, pgscan_kswapd) += nr_scan;
+ page_state(kswapd_steal) += nr_freed;
+ } else
+ page_state_zone(zone, pgscan_direct) += nr_scan;
+ page_state_zone(zone, pgsteal) += nr_freed;
+
+ spin_lock(&zone->lru_lock);
/*
* Put back any unfreeable pages.
*/
@@ -813,11 +814,13 @@ refill_inactive_zone(struct zone *zone,
}
}
zone->nr_active += pgmoved;
- spin_unlock_irq(&zone->lru_lock);
- pagevec_release(&pvec);
+ spin_unlock(&zone->lru_lock);
+
+ page_state_zone(zone, pgrefill) += pgscanned;
+ page_state(pgdeactivate) += pgdeactivate;
+ local_irq_enable();

- mod_page_state_zone(zone, pgrefill, pgscanned);
- mod_page_state(pgdeactivate, pgdeactivate);
+ pagevec_release(&pvec);
}

/*
Index: linux-2.6/mm/rmap.c
===================================================================
--- linux-2.6.orig/mm/rmap.c
+++ linux-2.6/mm/rmap.c
@@ -456,7 +456,11 @@ static void __page_set_anon_rmap(struct

page->index = linear_page_index(vma, address);

- inc_page_state(nr_mapped);
+ /*
+ * nr_mapped state can be updated without turning off
+ * interrupts because it is not modified via interrupt.
+ */
+ page_state(nr_mapped)++;
}

/**
@@ -503,7 +507,7 @@ void page_add_file_rmap(struct page *pag
BUG_ON(!pfn_valid(page_to_pfn(page)));

if (atomic_inc_and_test(&page->_mapcount))
- inc_page_state(nr_mapped);
+ page_state(nr_mapped)++;
}

/**
@@ -535,7 +539,7 @@ void page_remove_rmap(struct page *page)
* Leaving it set also helps swapoff to reinstate ptes
* faster for those pages still in swapcache.
*/
- dec_page_state(nr_mapped);
+ page_state(nr_mapped)--;
}

/*
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