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Subject[patch 04/20] free swap space on swap-in/activation
Free swap cache entries when swapping in pages if vm_swap_full()
[swap space > 1/2 used]. Uses new pagevec to reduce pressure
on locks.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>

Index: linux-2.6.25-rc3-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.25-rc3-mm1.orig/mm/vmscan.c 2008-03-04 15:25:52.000000000 -0500
+++ linux-2.6.25-rc3-mm1/mm/vmscan.c 2008-03-04 15:29:50.000000000 -0500
@@ -632,6 +632,9 @@ free_it:
continue;

activate_locked:
+ /* Not a candidate for swapping, so reclaim swap space. */
+ if (PageSwapCache(page) && vm_swap_full())
+ remove_exclusive_swap_page(page);
SetPageActive(page);
pgactivate++;
keep_locked:
@@ -1216,6 +1219,8 @@ static void shrink_active_list(unsigned
__mod_zone_page_state(zone, NR_ACTIVE, pgmoved);
pgmoved = 0;
spin_unlock_irq(&zone->lru_lock);
+ if (vm_swap_full())
+ pagevec_swap_free(&pvec);
__pagevec_release(&pvec);
spin_lock_irq(&zone->lru_lock);
}
@@ -1225,6 +1230,8 @@ static void shrink_active_list(unsigned
__count_zone_vm_events(PGREFILL, zone, pgscanned);
__count_vm_events(PGDEACTIVATE, pgdeactivate);
spin_unlock_irq(&zone->lru_lock);
+ if (vm_swap_full())
+ pagevec_swap_free(&pvec);

pagevec_release(&pvec);
}
Index: linux-2.6.25-rc3-mm1/mm/swap.c
===================================================================
--- linux-2.6.25-rc3-mm1.orig/mm/swap.c 2008-03-04 15:28:39.000000000 -0500
+++ linux-2.6.25-rc3-mm1/mm/swap.c 2008-03-04 15:29:50.000000000 -0500
@@ -457,6 +457,24 @@ void pagevec_strip(struct pagevec *pvec)
}
}

+/*
+ * Try to free swap space from the pages in a pagevec
+ */
+void pagevec_swap_free(struct pagevec *pvec)
+{
+ int i;
+
+ for (i = 0; i < pagevec_count(pvec); i++) {
+ struct page *page = pvec->pages[i];
+
+ if (PageSwapCache(page) && !TestSetPageLocked(page)) {
+ if (PageSwapCache(page))
+ remove_exclusive_swap_page(page);
+ unlock_page(page);
+ }
+ }
+}
+
/**
* pagevec_lookup - gang pagecache lookup
* @pvec: Where the resulting pages are placed
Index: linux-2.6.25-rc3-mm1/include/linux/pagevec.h
===================================================================
--- linux-2.6.25-rc3-mm1.orig/include/linux/pagevec.h 2008-03-04 15:26:18.000000000 -0500
+++ linux-2.6.25-rc3-mm1/include/linux/pagevec.h 2008-03-04 15:29:50.000000000 -0500
@@ -25,6 +25,7 @@ void __pagevec_release_nonlru(struct pag
void __pagevec_free(struct pagevec *pvec);
void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru);
void pagevec_strip(struct pagevec *pvec);
+void pagevec_swap_free(struct pagevec *pvec);
unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
pgoff_t start, unsigned nr_pages);
unsigned pagevec_lookup_tag(struct pagevec *pvec,
--
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