[PATCH 02/11] readahead: bump up the default readahead size

[Wu Fengguang <fengguang.wu@intel.com>]

[-- Attachment #1: readahead-enlarge-default-size.patch --]
[-- Type: text/plain, Size: 1120 bytes --]

Use 512kb max readahead size, and 32kb min readahead size.

The former helps io performance for common workloads.
The latter will be used in the thrashing safe context readahead.

CC: Jens Axboe <jens.axboe@oracle.com>
CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
CC: Martin Schwidefsky <schwidefsky@de.ibm.com>
CC: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 include/linux/mm.h |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- linux.orig/include/linux/mm.h	2010-01-30 17:38:49.000000000 +0800
+++ linux/include/linux/mm.h	2010-01-30 18:09:58.000000000 +0800
@@ -1184,8 +1184,8 @@ int write_one_page(struct page *page, in
 void task_dirty_inc(struct task_struct *tsk);
 
 /* readahead.c */
-#define VM_MAX_READAHEAD	128	/* kbytes */
-#define VM_MIN_READAHEAD	16	/* kbytes (includes current page) */
+#define VM_MAX_READAHEAD	512	/* kbytes */
+#define VM_MIN_READAHEAD	32	/* kbytes (includes current page) */
 
 int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
 			pgoff_t offset, unsigned long nr_to_read);