On Thursday 11 February 2010 16:45:24 Ankit Jain wrote: > > +static int __init readahead(char *str) > > +{ > > + if (!str) > > + return -EINVAL; > > + vm_max_readahead_kb = memparse(str, &str) / 1024ULL; > > Just wondering, shouldn't you check whether the str had a valid value > [memparse (str, &next); next > str ..] and if it didn't, then use the > DEFAULT_VM_MAX_READAHEAD ? Otherwise, incase of a invalid > value, the readahead value will become zero. > Thanks for the review. Here is the fixed patch that checks whether all of the parameters value is consumed. Thanks Nikanth From: Nikanth Karthikesan <knikanth@xxxxxxx> Add new kernel parameter "readahead", which would be used instead of the value of VM_MAX_READAHEAD. If the parameter is not specified, the default of 128kb would be used. Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx> --- diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 736d456..354e6f1 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2148,6 +2148,8 @@ and is between 256 and 4096 characters. It is defined in the file Format: <reboot_mode>[,<reboot_mode2>[,...]] See arch/*/kernel/reboot.c or arch/*/kernel/process.c + readahead= Default readahead value for block devices. + relax_domain_level= [KNL, SMP] Set scheduler's default relax_domain_level. See Documentation/cgroups/cpusets.txt. diff --git a/block/blk-core.c b/block/blk-core.c index 718897e..02ed748 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -499,7 +499,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) 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; + (vm_max_readahead_kb * 1024) / PAGE_CACHE_SIZE; q->backing_dev_info.state = 0; q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY; q->backing_dev_info.name = "block"; diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 1a822ce..a593578 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -870,7 +870,7 @@ static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb) int err; fc->bdi.name = "fuse"; - fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; + fc->bdi.ra_pages = (vm_max_readahead_kb * 1024) / PAGE_CACHE_SIZE; fc->bdi.unplug_io_fn = default_unplug_io_fn; /* fuse does it's own writeback accounting */ fc->bdi.capabilities = BDI_CAP_NO_ACCT_WB; diff --git a/include/linux/mm.h b/include/linux/mm.h index 60c467b..17825d7 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1188,9 +1188,11 @@ int write_one_page(struct page *page, int wait); void task_dirty_inc(struct task_struct *tsk); /* readahead.c */ -#define VM_MAX_READAHEAD 128 /* kbytes */ +#define DEFAULT_VM_MAX_READAHEAD 128 /* kbytes */ #define VM_MIN_READAHEAD 16 /* kbytes (includes current page) */ +extern unsigned long vm_max_readahead_kb; + int force_page_cache_readahead(struct address_space *mapping, struct file *filp, pgoff_t offset, unsigned long nr_to_read); diff --git a/init/main.c b/init/main.c index 4cb47a1..6c451d2 100644 --- a/init/main.c +++ b/init/main.c @@ -70,6 +70,7 @@ #include <linux/sfi.h> #include <linux/shmem_fs.h> #include <trace/boot.h> +#include <linux/backing-dev.h> #include <asm/io.h> #include <asm/bugs.h> @@ -249,6 +250,24 @@ static int __init loglevel(char *str) early_param("loglevel", loglevel); +static int __init readahead(char *str) +{ + unsigned long readahead_kb; + + if (!str) + return -EINVAL; + readahead_kb = memparse(str, &str) / 1024ULL; + if (*str != '\0') + return -EINVAL; + + vm_max_readahead_kb = readahead_kb; + default_backing_dev_info.ra_pages = vm_max_readahead_kb + * 1024 / PAGE_CACHE_SIZE; + return 0; +} + +early_param("readahead", readahead); + /* * Unknown boot options get handed to init, unless they look like * unused parameters (modprobe will find them in /proc/cmdline). diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 0e8ca03..e33ff34 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -18,7 +18,7 @@ EXPORT_SYMBOL(default_unplug_io_fn); struct backing_dev_info default_backing_dev_info = { .name = "default", - .ra_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE, + .ra_pages = DEFAULT_VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE, .state = 0, .capabilities = BDI_CAP_MAP_COPY, .unplug_io_fn = default_unplug_io_fn, diff --git a/mm/readahead.c b/mm/readahead.c index 033bc13..516f8da 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -17,6 +17,8 @@ #include <linux/pagevec.h> #include <linux/pagemap.h> +unsigned long vm_max_readahead_kb = DEFAULT_VM_MAX_READAHEAD; + /* * Initialise a struct file's readahead state. Assumes that the caller has * memset *ra to zero. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>