vmscan: split LRU lists into anon & file sets

Split the LRU lists in two, one set for pages that are backed by real file
systems ("file") and one for pages that are backed by memory and swap
("anon").  The latter includes tmpfs.

The advantage of doing this is that the VM will not have to scan over lots
of anonymous pages (which we generally do not want to swap out), just to
find the page cache pages that it should evict.

This patch has the infrastructure and a basic policy to balance how much
we scan the anon lists and how much we scan the file lists.  The big
policy changes are in separate patches.

[lee.schermerhorn@hp.com: collect lru meminfo statistics from correct offset]
[kosaki.motohiro@jp.fujitsu.com: prevent incorrect oom under split_lru]
[kosaki.motohiro@jp.fujitsu.com: fix pagevec_move_tail() doesn't treat unevictable page]
[hugh@veritas.com: memcg swapbacked pages active]
[hugh@veritas.com: splitlru: BDI_CAP_SWAP_BACKED]
[akpm@linux-foundation.org: fix /proc/vmstat units]
[nishimura@mxp.nes.nec.co.jp: memcg: fix handling of shmem migration]
[kosaki.motohiro@jp.fujitsu.com: adjust Quicklists field of /proc/meminfo]
[kosaki.motohiro@jp.fujitsu.com: fix style issue of get_scan_ratio()]
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 40 insertions, 7 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 156e18f3919b..59a4c8fd6ebd 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -82,21 +82,23 @@ enum zone_stat_item {
         /* First 128 byte cacheline (assuming 64 bit words) */
         NR_FREE_PAGES,
         NR_LRU_BASE,
-        NR_INACTIVE = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
-        NR_ACTIVE,      /*  "     "     "   "       "         */
+        NR_INACTIVE_ANON = NR_LRU_BASE, /* must match order of LRU_[IN]ACTIVE */
+        NR_ACTIVE_ANON,         /*  "     "     "   "       "         */
+        NR_INACTIVE_FILE,       /*  "     "     "   "       "         */
+        NR_ACTIVE_FILE,         /*  "     "     "   "       "         */
         NR_ANON_PAGES,  /* Mapped anonymous pages */
         NR_FILE_MAPPED, /* pagecache pages mapped into pagetables.
                            only modified from process context */
         NR_FILE_PAGES,
         NR_FILE_DIRTY,
         NR_WRITEBACK,
-        /* Second 128 byte cacheline */
         NR_SLAB_RECLAIMABLE,
         NR_SLAB_UNRECLAIMABLE,
         NR_PAGETABLE,           /* used for pagetables */
         NR_UNSTABLE_NFS,        /* NFS unstable pages */
         NR_BOUNCE,
         NR_VMSCAN_WRITE,
+        /* Second 128 byte cacheline */
         NR_WRITEBACK_TEMP,      /* Writeback using temporary buffers */
 #ifdef CONFIG_NUMA
         NUMA_HIT,               /* allocated in intended node */
@@ -108,17 +110,36 @@ 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.
+ *
+ * This has to be kept in sync with the statistics in zone_stat_item
+ * above and the descriptions in vmstat_text in mm/vmstat.c
+ */
+#define LRU_BASE 0
+#define LRU_ACTIVE 1
+#define LRU_FILE 2
+
 enum lru_list {
-        LRU_BASE,
-        LRU_INACTIVE=LRU_BASE,  /* must match order of NR_[IN]ACTIVE */
-        LRU_ACTIVE,             /*  "     "     "   "       "        */
+        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++)
 
+static inline int is_file_lru(enum lru_list l)
+{
+        return (l == LRU_INACTIVE_FILE || l == LRU_ACTIVE_FILE);
+}
+
 static inline int is_active_lru(enum lru_list l)
 {
-        return (l == LRU_ACTIVE);
+        return (l == LRU_ACTIVE_ANON || l == LRU_ACTIVE_FILE);
 }
 
 struct per_cpu_pages {
@@ -269,6 +290,18 @@ struct zone {
                 struct list_head list;
                 unsigned long nr_scan;
         } lru[NR_LRU_LISTS];
+
+        /*
+         * The pageout code in vmscan.c keeps track of how many of the
+         * mem/swap backed and file backed pages are refeferenced.
+         * The higher the rotated/scanned ratio, the more valuable
+         * that cache is.
+         *
+         * The anon LRU stats live in [0], file LRU stats in [1]
+         */
+        unsigned long           recent_rotated[2];
+        unsigned long           recent_scanned[2];
+
         unsigned long           pages_scanned;     /* since last reclaim */
         unsigned long           flags;             /* zone flags, see below */