[PATCH] Make high and batch sizes of per_cpu_pagelists configurable

As recently there has been lot of traffic on the right values for batch and
high water marks for per_cpu_pagelists.  This patch makes these two
variables configurable through /proc interface.

A new tunable /proc/sys/vm/percpu_pagelist_fraction is added.  This entry
controls the fraction of pages at most in each zone that are allocated for
each per cpu page list.  The min value for this is 8.  It means that we
don't allow more than 1/8th of pages in each zone to be allocated in any
single per_cpu_pagelist.

The batch value of each per cpu pagelist is also updated as a result.  It
is set to pcp->high/4.  The upper limit of batch is (PAGE_SHIFT * 8)

Signed-off-by: Rohit Seth <rohit.seth@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index c34f4a2c62f8..2a89c132ba9c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -437,6 +437,8 @@ int min_free_kbytes_sysctl_handler(struct ctl_table *, int, struct file *,
 extern int sysctl_lowmem_reserve_ratio[MAX_NR_ZONES-1];
 int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int, struct file *,
                                         void __user *, size_t *, loff_t *);
+int percpu_pagelist_fraction_sysctl_handler(struct ctl_table *, int, struct file *,
+                                        void __user *, size_t *, loff_t *);
 
 #include <linux/topology.h>
 /* Returns the number of the current Node. */
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 4cd267fe87ec..7f472127b7b5 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -181,6 +181,7 @@ enum
         VM_LEGACY_VA_LAYOUT=27, /* legacy/compatibility virtual address space layout */
         VM_SWAP_TOKEN_TIMEOUT=28, /* default time for token time out */
         VM_DROP_PAGECACHE=29,   /* int: nuke lots of pagecache */
+        VM_PERCPU_PAGELIST_FRACTION=30,/* int: fraction of pages in each percpu_pagelist */
 };