[RFC PATCH 2/10] free swap space entries if vm_swap_full()

Rik van Riel
2007-11-03T22:54:47Z

Rik van Riel's patch to free swap space on swap-in/activiation,
forward ported by Lee Schermerhorn.

Against: 2.6.23-rc2-mm2 atop:
+ lts' convert anon_vma list lock to reader/write lock patch
+ Nick Piggin's move and rework isolate_lru_page() patch

Patch Description: quick attempt by lts

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>

include/linux/pagevec.h | 1 +
mm/swap.c | 18 ++++++++++++++++++
mm/vmscan.c | 16 +++++++++++-----
3 files changed, 30 insertions(+), 5 deletions(-)

Index: linux-2.6.23-rc6-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.23-rc6-mm1.orig/mm/vmscan.c 2007-09-25 15:20:05.000000000 -0400
+++ linux-2.6.23-rc6-mm1/mm/vmscan.c 2007-09-25 15:25:04.000000000 -0400
@@ -613,6 +613,9 @@ 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:
@@ -1142,14 +1145,13 @@ force_reclaim_mapped:
}
}
__mod_zone_page_state(zone, NR_INACTIVE, pgmoved);
+ spin_unlock_irq(&zone->lru_lock);
pgdeactivate += pgmoved;
- if (buffer_heads_over_limit) {
- spin_unlock_irq(&zone->lru_lock);
- pagevec_strip(&pvec);
- spin_lock_irq(&zone->lru_lock);
- }

+ if (buffer_heads_over_limit)
+ pagevec_strip(&pvec);
pgmoved = 0;
+ spin_lock_irq(&zone->lru_lock);
while (!list_empty(&l_active)) {
page = lru_to_page(&l_active);
prefetchw_prev_lru_page(page, &l_active, flags);
@@ -1163,6 +1165,8 @@ 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);
}
@@ -1172,6 +1176,8 @@ force_reclaim_mapped:
__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-2.6.23-rc6-mm1/mm/swap.c
===================================================================
--- linux-2.6.23-rc6-mm1.orig/mm/swap.c 2007-09-25 15:20:05.000000000 -0400
+++ linux-2.6.23-rc6-mm1/mm/swap.c 2007-09-25 15:22:51.000000000 -0400
@@ -421,6 +421,24 @@ 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-2.6.23-rc6-mm1/include/linux/pagevec.h
===================================================================
--- linux-2.6.23-rc6-mm1.orig/include/linux/pagevec.h 2007-09-25 15:20:02.000000000 -0400
+++ linux-2.6.23-rc6-mm1/include/linux/pagevec.h 2007-09-25 15:22:51.000000000 -0400
@@ -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,