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SubjectRe: [PATCH] free swap space when (re)activating page
Rik van Riel wrote:

> ... because I think this is what my patch does :)

Never mind, I see it now.

The attached patch should be correct.

Btw, why do we not call pagevec_strip on the pages on l_active?
I assume we want to reclaim their buffer heads, too...

--
All Rights Reversed
--- linux-2.6.20.noarch/mm/vmscan.c.swapfree 2007-02-20 06:44:13.000000000 -0500
+++ linux-2.6.20.noarch/mm/vmscan.c 2007-02-20 06:54:10.000000000 -0500
@@ -587,6 +587,9 @@ 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:
@@ -889,6 +892,8 @@ force_reclaim_mapped:
__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);
}
@@ -899,6 +904,8 @@ force_reclaim_mapped:
__count_vm_events(PGDEACTIVATE, pgdeactivate);
spin_unlock_irq(&zone->lru_lock);

+ if (vm_swap_full())
+ pagevec_swap_free(&pvec);
pagevec_release(&pvec);
}

--- linux-2.6.20.noarch/mm/swap.c.swapfree 2007-02-04 13:44:54.000000000 -0500
+++ linux-2.6.20.noarch/mm/swap.c 2007-02-20 06:44:17.000000000 -0500
@@ -420,6 +420,26 @@ 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);
+ if (printk_ratelimit())
+ printk("kswapd freed a swap space\n");
+ }
+ }
+}
+
/**
* pagevec_lookup - gang pagecache lookup
* @pvec: Where the resulting pages are placed
--- linux-2.6.20.noarch/include/linux/pagevec.h.swapfree 2007-02-04 13:44:54.000000000 -0500
+++ linux-2.6.20.noarch/include/linux/pagevec.h 2007-02-20 06:44:17.000000000 -0500
@@ -26,6 +26,7 @@ void __pagevec_free(struct pagevec *pvec
void __pagevec_lru_add(struct pagevec *pvec);
void __pagevec_lru_add_active(struct pagevec *pvec);
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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