From: Nikanth Karthikesan <knikanth@xxxxxxx>
Add new kernel parameter "readahead=", which allows user to override
the static VM_MAX_READAHEAD=512kb.
CC: Ankit Jain <radical@xxxxxxxxx>
CC: Dave Chinner <david@xxxxxxxxxxxxx>
CC: Christian Ehrhardt <ehrhardt@xxxxxxxxxxxxxxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
Documentation/kernel-parameters.txt | 4 ++++
block/blk-core.c | 3 +--
fs/fuse/inode.c | 2 +-
mm/readahead.c | 22 ++++++++++++++++++++++
4 files changed, 28 insertions(+), 3 deletions(-)
--- linux.orig/Documentation/kernel-parameters.txt 2010-02-24 10:44:26.000000000 +0800
+++ linux/Documentation/kernel-parameters.txt 2010-02-24 10:44:42.000000000 +0800
@@ -2200,6 +2200,10 @@ and is between 256 and 4096 characters.
Run specified binary instead of /init from the ramdisk,
used for early userspace startup. See initrd.
+ readahead=nn[KM]
+ Default max readahead size for block devices.
+ Range: 0; 4k - 128m
+
reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Format: <reboot_mode>[,<reboot_mode2>[,...]]
See arch/*/kernel/reboot.c or arch/*/kernel/process.c
--- linux.orig/block/blk-core.c 2010-02-24 10:44:26.000000000 +0800
+++ linux/block/blk-core.c 2010-02-24 10:44:42.000000000 +0800
@@ -498,8 +498,7 @@ struct request_queue *blk_alloc_queue_no
q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
q->backing_dev_info.unplug_io_data = q;
- q->backing_dev_info.ra_pages =
- (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
+ q->backing_dev_info.ra_pages = default_backing_dev_info.ra_pages;
q->backing_dev_info.state = 0;
q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
q->backing_dev_info.name = "block";
--- linux.orig/fs/fuse/inode.c 2010-02-24 10:44:26.000000000 +0800
+++ linux/fs/fuse/inode.c 2010-02-24 10:44:42.000000000 +0800
@@ -870,7 +870,7 @@ static int fuse_bdi_init(struct fuse_con
int err;
fc->bdi.name = "fuse";
- fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
+ fc->bdi.ra_pages = default_backing_dev_info.ra_pages;
fc->bdi.unplug_io_fn = default_unplug_io_fn;
/* fuse does it's own writeback accounting */
fc->bdi.capabilities = BDI_CAP_NO_ACCT_WB;
--- linux.orig/mm/readahead.c 2010-02-24 10:44:40.000000000 +0800
+++ linux/mm/readahead.c 2010-02-24 10:44:42.000000000 +0800
@@ -19,6 +19,28 @@
#include <linux/pagevec.h>
#include <linux/pagemap.h>
+static int __init config_readahead_size(char *str)
+{
+ unsigned long bytes;
+
+ if (!str)
+ return -EINVAL;
+ bytes = memparse(str, &str);
+ if (*str != '\0')
+ return -EINVAL;
+
+ if (bytes) {
+ if (bytes < PAGE_CACHE_SIZE) /* missed 'k'/'m' suffixes? */
+ return -EINVAL;
+ if (bytes > 128 << 20) /* limit to 128MB */
+ bytes = 128 << 20;
+ }
+
+ default_backing_dev_info.ra_pages = bytes / PAGE_CACHE_SIZE;
+ return 0;
+}
+early_param("readahead", config_readahead_size);
+
/*
* Initialise a struct file's readahead state. Assumes that the caller has
* memset *ra to zero.
--
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