[RFC PATCH 7/10] clean up the LRU array arithmetic

Rik van Riel
2007-11-03T23:02:33Z

Make the LRU arithmetic more explicit. Hopefully this will make
the code a little easier to read and less prone to future errors.

Signed-off-by: Rik van Riel <riel@redhat.com>

Index: linux-2.6.23-mm1/include/linux/mm_inline.h
===================================================================
--- linux-2.6.23-mm1.orig/include/linux/mm_inline.h
+++ linux-2.6.23-mm1/include/linux/mm_inline.h
@@ -28,7 +28,7 @@ static inline int page_file_cache(struct
return 0;

/* The page is page cache backed by a normal filesystem. */
- return (LRU_INACTIVE_FILE - LRU_INACTIVE_ANON);
+ return LRU_FILE;
}

static inline void
Index: linux-2.6.23-mm1/mm/swap.c
===================================================================
--- linux-2.6.23-mm1.orig/mm/swap.c
+++ linux-2.6.23-mm1/mm/swap.c
@@ -180,12 +180,12 @@ void fastcall activate_page(struct page

spin_lock_irq(&zone->lru_lock);
if (PageLRU(page) && !PageActive(page)) {
- int l = LRU_INACTIVE_ANON;
+ int l = LRU_BASE;
l += page_file_cache(page);
del_page_from_lru_list(zone, page, l);

SetPageActive(page);
- l += LRU_ACTIVE_ANON - LRU_INACTIVE_ANON;
+ l += LRU_ACTIVE;
add_page_to_lru_list(zone, page, l);
__count_vm_event(PGACTIVATE);
mem_cgroup_move_lists(page_get_page_cgroup(page), true);
Index: linux-2.6.23-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.23-mm1.orig/mm/vmscan.c
+++ linux-2.6.23-mm1/mm/vmscan.c
@@ -786,11 +786,11 @@ static unsigned long isolate_pages_globa
struct mem_cgroup *mem_cont,
int active, int file)
{
- int l = LRU_INACTIVE_ANON;
+ int l = LRU_BASE;
if (active)
- l += LRU_ACTIVE_ANON - LRU_INACTIVE_ANON;
+ l += LRU_ACTIVE;
if (file)
- l += LRU_INACTIVE_FILE - LRU_INACTIVE_ANON;
+ l += LRU_FILE;
return isolate_lru_pages(nr, &z->list[l], dst, scanned, order,
mode, !!file);
}
@@ -842,7 +842,7 @@ int isolate_lru_page(struct page *page)

spin_lock_irq(&zone->lru_lock);
if (PageLRU(page) && get_page_unless_zero(page)) {
- int l = LRU_INACTIVE_ANON;
+ int l = LRU_BASE;
ret = 0;
ClearPageLRU(page);

@@ -938,19 +938,19 @@ static unsigned long shrink_inactive_lis
* Put back any unfreeable pages.
*/
while (!list_empty(&page_list)) {
- int l = LRU_INACTIVE_ANON;
+ int l = LRU_BASE;
page = lru_to_page(&page_list);
VM_BUG_ON(PageLRU(page));
SetPageLRU(page);
list_del(&page->lru);
if (file) {
- l += LRU_INACTIVE_FILE - LRU_INACTIVE_ANON;
+ l += LRU_FILE;
zone->recent_rotated_file += sc->activated;
} else {
zone->recent_rotated_anon += sc->activated;
}
if (PageActive(page))
- l += LRU_ACTIVE_ANON - LRU_INACTIVE_ANON;
+ l += LRU_ACTIVE;
add_page_to_lru_list(zone, page, l);
if (!pagevec_add(&pvec, page)) {
spin_unlock_irq(&zone->lru_lock);
@@ -1051,7 +1051,7 @@ static void shrink_active_list(unsigned
*/
pagevec_init(&pvec, 1);
pgmoved = 0;
- l = LRU_INACTIVE_ANON + file * (LRU_INACTIVE_FILE - LRU_INACTIVE_ANON);
+ l = LRU_BASE + file * LRU_FILE;
spin_lock_irq(&zone->lru_lock);
while (!list_empty(&list[LRU_INACTIVE_ANON])) {
page = lru_to_page(&list[LRU_INACTIVE_ANON]);
@@ -1083,7 +1083,7 @@ static void shrink_active_list(unsigned
if (buffer_heads_over_limit)
pagevec_strip(&pvec);
pgmoved = 0;
- l = LRU_ACTIVE_ANON + file * (LRU_ACTIVE_FILE - LRU_ACTIVE_ANON);
+ l = LRU_ACTIVE + file * LRU_FILE;
spin_lock_irq(&zone->lru_lock);
while (!list_empty(&list[LRU_ACTIVE_ANON])) {
page = lru_to_page(&list[LRU_ACTIVE_ANON]);
Index: linux-2.6.23-mm1/include/linux/mmzone.h
===================================================================
--- linux-2.6.23-mm1.orig/include/linux/mmzone.h
+++ linux-2.6.23-mm1/include/linux/mmzone.h
@@ -107,11 +107,22 @@ enum zone_stat_item {
#endif
NR_VM_ZONE_STAT_ITEMS };

+/*
+ * We do arithmetic on the LRU lists in various places in the code,
+ * so it is important to keep the active lists LRU_ACTIVE higher in
+ * the array than the corresponding inactive lists, and to keep
+ * the *_FILE lists LRU_FILE higher than the corresponding _ANON lists.
+ */
+#define LRU_BASE 0
+#define LRU_ANON LRU_BASE
+#define LRU_ACTIVE 1
+#define LRU_FILE 2
+
enum lru_list {
- LRU_INACTIVE_ANON, /* must be first enum */
- LRU_ACTIVE_ANON, /* must match order of NR_[IN]ACTIVE_* */
- LRU_INACTIVE_FILE, /* " " " " " */
- LRU_ACTIVE_FILE, /* " " " " " */
+ LRU_INACTIVE_ANON = LRU_BASE,
+ LRU_ACTIVE_ANON = LRU_BASE + LRU_ACTIVE,
+ LRU_INACTIVE_FILE = LRU_BASE + LRU_FILE,
+ LRU_ACTIVE_FILE = LRU_BASE + LRU_FILE + LRU_ACTIVE,
NR_LRU_LISTS };

#define for_each_lru(l) for (l = 0; l < NR_LRU_LISTS; l++)