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SubjectRe: [PATCH 5/5] linear reclaim core
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On Fri, 2006-09-08 at 11:41 -0700, Andrew Morton wrote:

> - Pick tail page off LRU.
>
> - For all "neighbour" pages (alignment == 1<<order, count == 1<<order)
>
> - If they're all PageLRU and !PageActive, add them all to page_list for
> possible reclaim
>
> And, in shrink_active_list:
>
> - Pick tail page off LRU
>
> - For all "neighbour" pages (alignment == 1<<order, count == 1<<order)
>
> If they're all PageLRU, put all the active pages in this block onto
> l_hold for possible deactivation.
>
>
> Maybe all that can be done in isolate_lru_pages().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
fs/buffer.c | 2 -
include/linux/swap.h | 2 -
mm/page_alloc.c | 2 -
mm/vmscan.c | 70 ++++++++++++++++++++++++++++++++++++---------------
4 files changed, 53 insertions(+), 23 deletions(-)

Index: linux-2.6/mm/vmscan.c
===================================================================
--- linux-2.6.orig/mm/vmscan.c 2006-07-22 00:11:00.000000000 +0200
+++ linux-2.6/mm/vmscan.c 2006-09-10 11:47:05.000000000 +0200
@@ -62,6 +62,8 @@ struct scan_control {
int swap_cluster_max;

int swappiness;
+
+ int order;
};

/*
@@ -590,35 +592,62 @@ keep:
*
* returns how many pages were moved onto *@dst.
*/
+int __isolate_lru_page(struct page *page, int active)
+{
+ int ret = -EINVAL;
+
+ if (PageLRU(page) && (PageActive(page) == active)) {
+ ret = -EBUSY;
+ if (likely(get_page_unless_zero(page))) {
+ /*
+ * Be careful not to clear PageLRU until after we're
+ * sure the page is not being freed elsewhere -- the
+ * page release code relies on it.
+ */
+ ClearPageLRU(page);
+ ret = 0;
+ }
+ }
+
+ return ret;
+}
+
static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
struct list_head *src, struct list_head *dst,
- unsigned long *scanned)
+ unsigned long *scanned, int order)
{
unsigned long nr_taken = 0;
struct page *page;
- unsigned long scan;
+ unsigned long scan, pfn, base_pfn;
+ int active;

- for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
- struct list_head *target;
+ for (scan = 0; scan < nr_to_scan && !list_empty(src);) {
page = lru_to_page(src);
prefetchw_prev_lru_page(page, src, flags);

BUG_ON(!PageLRU(page));

- list_del(&page->lru);
- target = src;
- if (likely(get_page_unless_zero(page))) {
- /*
- * Be careful not to clear PageLRU until after we're
- * sure the page is not being freed elsewhere -- the
- * page release code relies on it.
- */
- ClearPageLRU(page);
- target = dst;
+ active = PageActive(page);
+ pfn = page_to_pfn(page);
+ base_pfn = pfn &= ~((1 << order) - 1);
+ for (; pfn < (base_pfn + (1 << order)) && pfn_valid(pfn); pfn++) {
+ struct page *tmp = pfn_to_page(pfn);
+ int ret;
+
+ BUG_ON(!tmp);
+
+ ret = __isolate_lru_page(tmp, active);
+ scan++;
+ if (ret) {
+ if (ret == -EBUSY) {
+ /* else it is being freed elsewhere */
+ list_move(&tmp->lru, src);
+ }
+ break;
+ } else
+ list_move(&tmp->lru, dst);
nr_taken++;
- } /* else it is being freed elsewhere */
-
- list_add(&page->lru, target);
+ }
}

*scanned = scan;
@@ -649,7 +678,7 @@ static unsigned long shrink_inactive_lis

nr_taken = isolate_lru_pages(sc->swap_cluster_max,
&zone->inactive_list,
- &page_list, &nr_scan);
+ &page_list, &nr_scan, sc->order);
zone->nr_inactive -= nr_taken;
zone->pages_scanned += nr_scan;
spin_unlock_irq(&zone->lru_lock);
@@ -771,7 +800,7 @@ static void shrink_active_list(unsigned
lru_add_drain();
spin_lock_irq(&zone->lru_lock);
pgmoved = isolate_lru_pages(nr_pages, &zone->active_list,
- &l_hold, &pgscanned);
+ &l_hold, &pgscanned, sc->order);
zone->pages_scanned += pgscanned;
zone->nr_active -= pgmoved;
spin_unlock_irq(&zone->lru_lock);
@@ -959,7 +988,7 @@ static unsigned long shrink_zones(int pr
* holds filesystem locks which prevent writeout this might not work, and the
* allocation attempt will fail.
*/
-unsigned long try_to_free_pages(struct zone **zones, gfp_t gfp_mask)
+unsigned long try_to_free_pages(struct zone **zones, int order, gfp_t gfp_mask)
{
int priority;
int ret = 0;
@@ -974,6 +1003,7 @@ unsigned long try_to_free_pages(struct z
.swap_cluster_max = SWAP_CLUSTER_MAX,
.may_swap = 1,
.swappiness = vm_swappiness,
+ .order = order,
};

count_vm_event(ALLOCSTALL);
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c 2006-09-08 18:13:56.000000000 +0200
+++ linux-2.6/fs/buffer.c 2006-09-09 23:55:21.000000000 +0200
@@ -498,7 +498,7 @@ static void free_more_memory(void)
for_each_online_pgdat(pgdat) {
zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
if (*zones)
- try_to_free_pages(zones, GFP_NOFS);
+ try_to_free_pages(zones, 0, GFP_NOFS);
}
}

Index: linux-2.6/include/linux/swap.h
===================================================================
--- linux-2.6.orig/include/linux/swap.h 2006-09-08 18:13:56.000000000 +0200
+++ linux-2.6/include/linux/swap.h 2006-09-09 23:53:56.000000000 +0200
@@ -181,7 +181,7 @@ extern int rotate_reclaimable_page(struc
extern void swap_setup(void);

/* linux/mm/vmscan.c */
-extern unsigned long try_to_free_pages(struct zone **, gfp_t);
+extern unsigned long try_to_free_pages(struct zone **, int, gfp_t);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
extern int vm_swappiness;
extern int remove_mapping(struct address_space *mapping, struct page *page);
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c 2006-09-08 18:13:57.000000000 +0200
+++ linux-2.6/mm/page_alloc.c 2006-09-09 23:55:04.000000000 +0200
@@ -1000,7 +1000,7 @@ rebalance:
reclaim_state.reclaimed_slab = 0;
p->reclaim_state = &reclaim_state;

- did_some_progress = try_to_free_pages(zonelist->zones, gfp_mask);
+ did_some_progress = try_to_free_pages(zonelist->zones, order, gfp_mask);

p->reclaim_state = NULL;
p->flags &= ~PF_MEMALLOC;

-
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