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Subject[PATCH 02/03] Unmapped: Modify LRU behaviour
Date
Move reclaim_mapped logic, sc->nr_mapped, keep active unmapped pages.

This patch moves the reclaim_mapped logic from refill_inactive_zone() to
shrink_zone(), where it is used to determine if the mapped LRU should be
scanned or not. The sc->nr_mapped member is removed and replaced with code
that checks the number of pages placed on the per-zone mapped LRU.
refill_inactive_zone is changed to allow rotate of active unmapped pages.

Signed-off-by: Magnus Damm <magnus@valinux.co.jp>
---
vmscan.c | 106 +++++++++++++++++++++++++++++---------------------------------
1 files changed, 51 insertions(+), 55 deletions(-)
--- from-0003/mm/vmscan.c
+++ to-work/mm/vmscan.c 2006-03-06 16:58:27.000000000 +0900
@@ -61,8 +61,6 @@ struct scan_control {
/* Incremented by the number of pages reclaimed */
unsigned long nr_reclaimed;

- unsigned long nr_mapped; /* From page_state */
-
/* Ask shrink_caches, or shrink_zone to scan at this priority */
unsigned int priority;

@@ -1202,48 +1200,6 @@ refill_inactive_zone(struct zone *zone,
LIST_HEAD(l_active); /* Pages to go onto the active_list */
struct page *page;
struct pagevec pvec;
- int reclaim_mapped = 0;
-
- if (unlikely(sc->may_swap)) {
- long mapped_ratio;
- long distress;
- long swap_tendency;
-
- /*
- * `distress' is a measure of how much trouble we're having
- * reclaiming pages. 0 -> no problems. 100 -> great trouble.
- */
- distress = 100 >> zone->prev_priority;
-
- /*
- * The point of this algorithm is to decide when to start
- * reclaiming mapped memory instead of just pagecache. Work out
- * how much memory
- * is mapped.
- */
- mapped_ratio = (sc->nr_mapped * 100) / total_memory;
-
- /*
- * Now decide how much we really want to unmap some pages. The
- * mapped ratio is downgraded - just because there's a lot of
- * mapped memory doesn't necessarily mean that page reclaim
- * isn't succeeding.
- *
- * The distress ratio is important - we don't want to start
- * going oom.
- *
- * A 100% value of vm_swappiness overrides this algorithm
- * altogether.
- */
- swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
-
- /*
- * Now use this metric to decide whether to start moving mapped
- * memory onto the inactive list.
- */
- if (swap_tendency >= 100)
- reclaim_mapped = 1;
- }

lru_add_drain();
spin_lock_irq(&zone->lru_lock);
@@ -1257,13 +1213,10 @@ refill_inactive_zone(struct zone *zone,
cond_resched();
page = lru_to_page(&l_hold);
list_del(&page->lru);
- if (page_mapped(page)) {
- if (!reclaim_mapped ||
- (total_swap_pages == 0 && PageAnon(page)) ||
- page_referenced(page, 0)) {
- list_add(&page->lru, &l_active);
- continue;
- }
+ if ((total_swap_pages == 0 && PageAnon(page)) ||
+ page_referenced(page, 0)) {
+ list_add(&page->lru, &l_active);
+ continue;
}
list_add(&page->lru, &l_inactive);
}
@@ -1378,8 +1331,54 @@ shrink_lru(struct zone *zone, int lru_nr
static void
shrink_zone(struct zone *zone, struct scan_control *sc)
{
+ int reclaim_mapped = 0;
+
+ if (unlikely(sc->may_swap)) {
+ struct lru *lru = &zone->lru[LRU_MAPPED];
+ long mapped_ratio;
+ long distress;
+ long swap_tendency;
+
+ /*
+ * `distress' is a measure of how much trouble we're having
+ * reclaiming pages. 0 -> no problems. 100 -> great trouble.
+ */
+ distress = 100 >> zone->prev_priority;
+
+ /*
+ * The point of this algorithm is to decide when to start
+ * reclaiming mapped memory instead of just pagecache.
+ * Work out how much memory is mapped.
+ */
+ mapped_ratio = (lru->nr_active + lru->nr_inactive) * 100;
+ mapped_ratio /= zone->present_pages;
+
+ /*
+ * Now decide how much we really want to unmap some pages. The
+ * mapped ratio is downgraded - just because there's a lot of
+ * mapped memory doesn't necessarily mean that page reclaim
+ * isn't succeeding.
+ *
+ * The distress ratio is important - we don't want to start
+ * going oom.
+ *
+ * A 100% value of vm_swappiness overrides this algorithm
+ * altogether.
+ */
+ swap_tendency = mapped_ratio / 2 + distress + vm_swappiness;
+
+ /*
+ * Now use this metric to decide whether to start moving mapped
+ * memory onto the inactive list.
+ */
+ if (swap_tendency >= 100)
+ reclaim_mapped = 1;
+ }
+
shrink_lru(zone, LRU_UNMAPPED, sc);
- shrink_lru(zone, LRU_MAPPED, sc);
+
+ if (reclaim_mapped)
+ shrink_lru(zone, LRU_MAPPED, sc);
}

/*
@@ -1463,7 +1462,6 @@ int try_to_free_pages(struct zone **zone
}

for (priority = DEF_PRIORITY; priority >= 0; priority--) {
- sc.nr_mapped = read_page_state(nr_mapped);
sc.nr_scanned = 0;
sc.nr_reclaimed = 0;
sc.priority = priority;
@@ -1552,7 +1550,6 @@ loop_again:
sc.gfp_mask = GFP_KERNEL;
sc.may_writepage = !laptop_mode;
sc.may_swap = 1;
- sc.nr_mapped = read_page_state(nr_mapped);

inc_page_state(pageoutrun);

@@ -1910,7 +1907,6 @@ int zone_reclaim(struct zone *zone, gfp_
sc.nr_scanned = 0;
sc.nr_reclaimed = 0;
sc.priority = ZONE_RECLAIM_PRIORITY + 1;
- sc.nr_mapped = read_page_state(nr_mapped);
sc.gfp_mask = gfp_mask;

disable_swap_token();
-
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