mm: Add NR_WRITEBACK_TEMP counter

Fuse will use temporary buffers to write back dirty data from memory mappings
(normal writes are done synchronously).  This is needed, because there cannot
be any guarantee about the time in which a write will complete.

By using temporary buffers, from the MM's point if view the page is written
back immediately.  If the writeout was due to memory pressure, this
effectively migrates data from a full zone to a less full zone.

This patch adds a new counter (NR_WRITEBACK_TEMP) for the number of pages used
as temporary buffers.

[Lee.Schermerhorn@hp.com: add vmstat_text for NR_WRITEBACK_TEMP]
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/base/node.c b/drivers/base/node.c
index 12fde2d03d695a112f02debd25c4fb897a4b937c..39f3d1b3a21354aa112f5fb222b862d99daafb04 100644 (file)
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -77,6 +77,7 @@ static ssize_t node_read_meminfo(struct sys_device * dev, char * buf)
                       "Node %d PageTables:   %8lu kB\n"
                       "Node %d NFS_Unstable: %8lu kB\n"
                       "Node %d Bounce:       %8lu kB\n"
+                      "Node %d WritebackTmp: %8lu kB\n"
                       "Node %d Slab:         %8lu kB\n"
                       "Node %d SReclaimable: %8lu kB\n"
                       "Node %d SUnreclaim:   %8lu kB\n",
@@ -99,6 +100,7 @@ static ssize_t node_read_meminfo(struct sys_device * dev, char * buf)
                       nid, K(node_page_state(nid, NR_PAGETABLE)),
                       nid, K(node_page_state(nid, NR_UNSTABLE_NFS)),
                       nid, K(node_page_state(nid, NR_BOUNCE)),
+                      nid, K(node_page_state(nid, NR_WRITEBACK_TEMP)),
                       nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE) +
                                node_page_state(nid, NR_SLAB_UNRECLAIMABLE)),
                       nid, K(node_page_state(nid, NR_SLAB_RECLAIMABLE)),

diff --git a/fs/proc/proc_misc.c b/fs/proc/proc_misc.c
index 48bcf20cec2f815c6f6c8763cdb2937a8576d796..74a323d2b850884f06c2206fc4d288e957c8bef6 100644 (file)
--- a/fs/proc/proc_misc.c
+++ b/fs/proc/proc_misc.c
@@ -179,6 +179,7 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
                "PageTables:   %8lu kB\n"
                "NFS_Unstable: %8lu kB\n"
                "Bounce:       %8lu kB\n"
+               "WritebackTmp: %8lu kB\n"
                "CommitLimit:  %8lu kB\n"
                "Committed_AS: %8lu kB\n"
                "VmallocTotal: %8lu kB\n"
@@ -210,6 +211,7 @@ static int meminfo_read_proc(char *page, char **start, off_t off,
                K(global_page_state(NR_PAGETABLE)),
                K(global_page_state(NR_UNSTABLE_NFS)),
                K(global_page_state(NR_BOUNCE)),
+               K(global_page_state(NR_WRITEBACK_TEMP)),
                K(allowed),
                K(committed),
                (unsigned long)VMALLOC_TOTAL >> 10,

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index aad98003176f895ab9c361765109f981fe25be20..ceb675d83a565c5642e35fbe9bc27db41452c0a7 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -97,6 +97,7 @@ enum zone_stat_item {
        NR_UNSTABLE_NFS,        /* NFS unstable pages */
        NR_BOUNCE,
        NR_VMSCAN_WRITE,
+       NR_WRITEBACK_TEMP,      /* Writeback using temporary buffers */
 #ifdef CONFIG_NUMA
        NUMA_HIT,               /* allocated in intended node */
        NUMA_MISS,              /* allocated in non intended node */

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index c90a1e8e479f1ce0bb1633f0f13c1535f213b98e..789b6adbef37f1f38c3887f10ba130595903408a 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -211,7 +211,8 @@ clip_bdi_dirty_limit(struct backing_dev_info *bdi, long dirty, long *pbdi_dirty)
        avail_dirty = dirty -
                (global_page_state(NR_FILE_DIRTY) +
                 global_page_state(NR_WRITEBACK) +
-                global_page_state(NR_UNSTABLE_NFS));
+                global_page_state(NR_UNSTABLE_NFS) +
+                global_page_state(NR_WRITEBACK_TEMP));
 
        if (avail_dirty < 0)
                avail_dirty = 0;

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 280a7ed549f2efc6cf436cc1c2af1b83eb33f439..1a32130b958c418ec8a018aa676c73bb3d7cde32 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -612,6 +612,7 @@ static const char * const vmstat_text[] = {
        "nr_unstable",
        "nr_bounce",
        "nr_vmscan_write",
+       "nr_writeback_temp",
 
 #ifdef CONFIG_NUMA
        "numa_hit",