From: Nikanth Karthikesan Add new kernel parameter "readahead", which allows user to override the static VM_MAX_READAHEAD=512kb. CC: Ankit Jain CC: Dave Chinner CC: Christian Ehrhardt Signed-off-by: Nikanth Karthikesan Signed-off-by: Wu Fengguang --- 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: [,[,...]] 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 #include +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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/