Hi,
This is yet another implementation of the PG_useonce cleanup spoken of
during the VM summit.
The idea is to mark a page PG_useonce on pagecache entry and modify the
page_referenced() check to retry on the inactive list instead of
promotion to the active list when PG_useonce is set. PG_useonce is
cleared on first use.
Signed-off-by: Peter Zijlstra <[email protected]>
---
include/linux/mm_inline.h | 2 ++
include/linux/page-flags.h | 5 +++++
mm/filemap.c | 22 +++++++++++++---------
mm/page_alloc.c | 9 ++++++---
mm/shmem.c | 7 ++-----
mm/swap.c | 11 ++---------
mm/vmscan.c | 36 +++++++++++-------------------------
7 files changed, 41 insertions(+), 51 deletions(-)
Index: linux-2.6/include/linux/mm_inline.h
===================================================================
--- linux-2.6.orig/include/linux/mm_inline.h 2006-07-17 22:31:06.000000000 +0200
+++ linux-2.6/include/linux/mm_inline.h 2006-07-17 22:35:32.000000000 +0200
@@ -37,5 +37,7 @@ del_page_from_lru(struct zone *zone, str
} else {
zone->nr_inactive--;
}
+ if (PageUseOnce(page))
+ ClearPageUseOnce(page);
}
Index: linux-2.6/include/linux/page-flags.h
===================================================================
--- linux-2.6.orig/include/linux/page-flags.h 2006-07-17 22:31:09.000000000 +0200
+++ linux-2.6/include/linux/page-flags.h 2006-07-17 22:39:14.000000000 +0200
@@ -86,6 +86,7 @@
#define PG_nosave_free 18 /* Free, should not be written */
#define PG_buddy 19 /* Page is free, on buddy lists */
+#define PG_useonce 20 /* Page is new to the pagecache */
#if (BITS_PER_LONG > 32)
/*
@@ -247,6 +248,10 @@
#define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags)
#define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)
+#define PageUseOnce(page) test_bit(PG_useonce, &(page)->flags)
+#define SetPageUseOnce(page) set_bit(PG_useonce, &(page)->flags)
+#define ClearPageUseOnce(page) clear_bit(PG_useonce, &(page)->flags)
+
struct page; /* forward declaration */
int test_clear_page_dirty(struct page *page);
Index: linux-2.6/mm/filemap.c
===================================================================
--- linux-2.6.orig/mm/filemap.c 2006-07-17 22:31:17.000000000 +0200
+++ linux-2.6/mm/filemap.c 2006-07-17 22:35:32.000000000 +0200
@@ -444,6 +444,18 @@ int add_to_page_cache(struct page *page,
error = radix_tree_insert(&mapping->page_tree, offset, page);
if (!error) {
page_cache_get(page);
+ /*
+ * shmem_getpage()
+ * lookup_swap_cache()
+ * TestSetPageLocked()
+ * move_from_swap_cache()
+ * add_to_page_cache()
+ *
+ * That path calls us with a LRU page instead of a new
+ * page. Don't set the hint for LRU pages.
+ */
+ if (!PageLocked(page))
+ SetPageUseOnce(page);
SetPageLocked(page);
page->mapping = mapping;
page->index = offset;
@@ -884,7 +896,6 @@ void do_generic_mapping_read(struct addr
unsigned long offset;
unsigned long last_index;
unsigned long next_index;
- unsigned long prev_index;
loff_t isize;
struct page *cached_page;
int error;
@@ -893,7 +904,6 @@ void do_generic_mapping_read(struct addr
cached_page = NULL;
index = *ppos >> PAGE_CACHE_SHIFT;
next_index = index;
- prev_index = ra.prev_page;
last_index = (*ppos + desc->count + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
offset = *ppos & ~PAGE_CACHE_MASK;
@@ -940,13 +950,7 @@ page_ok:
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
- /*
- * When (part of) the same page is read multiple times
- * in succession, only mark it as accessed the first time.
- */
- if (prev_index != index)
- mark_page_accessed(page);
- prev_index = index;
+ mark_page_accessed(page);
/*
* Ok, we have the page, and it's up-to-date, so
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c 2006-07-17 22:31:17.000000000 +0200
+++ linux-2.6/mm/page_alloc.c 2006-07-17 22:38:25.000000000 +0200
@@ -154,7 +154,8 @@ static void bad_page(struct page *page)
1 << PG_slab |
1 << PG_swapcache |
1 << PG_writeback |
- 1 << PG_buddy );
+ 1 << PG_buddy |
+ 1 << PG_useonce);
set_page_count(page, 0);
reset_page_mapcount(page);
page->mapping = NULL;
@@ -389,7 +390,8 @@ static inline int free_pages_check(struc
1 << PG_swapcache |
1 << PG_writeback |
1 << PG_reserved |
- 1 << PG_buddy ))))
+ 1 << PG_buddy |
+ 1 << PF_useonce ))))
bad_page(page);
if (PageDirty(page))
__ClearPageDirty(page);
@@ -538,7 +540,8 @@ static int prep_new_page(struct page *pa
1 << PG_swapcache |
1 << PG_writeback |
1 << PG_reserved |
- 1 << PG_buddy ))))
+ 1 << PG_buddy |
+ 1 << PG_useonce ))))
bad_page(page);
/*
Index: linux-2.6/mm/shmem.c
===================================================================
--- linux-2.6.orig/mm/shmem.c 2006-07-17 22:31:17.000000000 +0200
+++ linux-2.6/mm/shmem.c 2006-07-17 22:35:32.000000000 +0200
@@ -1567,11 +1567,8 @@ static void do_shmem_file_read(struct fi
*/
if (mapping_writably_mapped(mapping))
flush_dcache_page(page);
- /*
- * Mark the page accessed if we read the beginning.
- */
- if (!offset)
- mark_page_accessed(page);
+
+ mark_page_accessed(page);
} else {
page = ZERO_PAGE(0);
page_cache_get(page);
Index: linux-2.6/mm/swap.c
===================================================================
--- linux-2.6.orig/mm/swap.c 2006-07-17 22:31:18.000000000 +0200
+++ linux-2.6/mm/swap.c 2006-07-17 22:35:32.000000000 +0200
@@ -114,19 +114,11 @@ void fastcall activate_page(struct page
/*
* Mark a page as having seen activity.
- *
- * inactive,unreferenced -> inactive,referenced
- * inactive,referenced -> active,unreferenced
- * active,unreferenced -> active,referenced
*/
void fastcall mark_page_accessed(struct page *page)
{
- if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
- activate_page(page);
- ClearPageReferenced(page);
- } else if (!PageReferenced(page)) {
+ if (!PageReferenced(page))
SetPageReferenced(page);
- }
}
EXPORT_SYMBOL(mark_page_accessed);
@@ -153,6 +145,7 @@ void fastcall lru_cache_add_active(struc
struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
page_cache_get(page);
+ ClearPageUseOnce(page);
if (!pagevec_add(pvec, page))
__pagevec_lru_add_active(pvec);
put_cpu_var(lru_add_active_pvecs);
Index: linux-2.6/mm/vmscan.c
===================================================================
--- linux-2.6.orig/mm/vmscan.c 2006-07-17 22:31:18.000000000 +0200
+++ linux-2.6/mm/vmscan.c 2006-07-17 22:35:32.000000000 +0200
@@ -227,27 +227,6 @@ unsigned long shrink_slab(unsigned long
return ret;
}
-/* Called without lock on whether page is mapped, so answer is unstable */
-static inline int page_mapping_inuse(struct page *page)
-{
- struct address_space *mapping;
-
- /* Page is in somebody's page tables. */
- if (page_mapped(page))
- return 1;
-
- /* Be more reluctant to reclaim swapcache than pagecache */
- if (PageSwapCache(page))
- return 1;
-
- mapping = page_mapping(page);
- if (!mapping)
- return 0;
-
- /* File is mmap'd by somebody? */
- return mapping_mapped(mapping);
-}
-
static inline int is_page_cache_freeable(struct page *page)
{
return page_count(page) - !!PagePrivate(page) == 2;
@@ -456,8 +435,13 @@ static unsigned long shrink_page_list(st
referenced = page_referenced(page, 1);
/* In active use or really unfreeable? Activate it. */
- if (referenced && page_mapping_inuse(page))
+ if (referenced) {
+ if (PageUseOnce(page)) {
+ ClearPageUseOnce(page);
+ goto keep_locked;
+ }
goto activate_locked;
+ }
#ifdef CONFIG_SWAP
/*
@@ -551,6 +535,7 @@ static unsigned long shrink_page_list(st
goto keep_locked;
free_it:
+ ClearPageUseOnce(page);
unlock_page(page);
nr_reclaimed++;
if (!pagevec_add(&freed_pvec, page))
@@ -724,6 +709,7 @@ static void shrink_active_list(unsigned
struct page *page;
struct pagevec pvec;
int reclaim_mapped = 0;
+ int referenced;
if (sc->may_swap) {
long mapped_ratio;
@@ -780,10 +766,10 @@ static void shrink_active_list(unsigned
cond_resched();
page = lru_to_page(&l_hold);
list_del(&page->lru);
+ referenced = page_referenced(page, 0);
if (page_mapped(page)) {
- if (!reclaim_mapped ||
- (total_swap_pages == 0 && PageAnon(page)) ||
- page_referenced(page, 0)) {
+ if (referenced || !reclaim_mapped ||
+ (total_swap_pages == 0 && PageAnon(page))) {
list_add(&page->lru, &l_active);
continue;
}
-
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