Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754368Ab0BIL3M (ORCPT ); Tue, 9 Feb 2010 06:29:12 -0500 Received: from cantor.suse.de ([195.135.220.2]:43409 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754159Ab0BIL3J (ORCPT ); Tue, 9 Feb 2010 06:29:09 -0500 From: Nikanth Karthikesan Organization: suse.de To: Andrew Morton Subject: [PATCH] Make vm_max_readahead configurable at run-time Date: Tue, 9 Feb 2010 16:59:26 +0530 User-Agent: KMail/1.12.2 (Linux/2.6.31.8-0.1-desktop; KDE/4.3.1; x86_64; ; ) Cc: Jens Axboe , linux-kernel@vger.kernel.org, linux-mm@kvack.org MIME-Version: 1.0 Content-Type: Text/Plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Message-Id: <201002091659.27037.knikanth@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4764 Lines: 137 Make vm_max_readahead configurable at run-time. Expose a sysctl knob in procfs to change it. This would ensure that new disks added would use this value as their default read_ahead_kb. Signed-off-by: Nikanth Karthikesan --- Index: linux-2.6/block/blk-core.c =================================================================== --- linux-2.6.orig/block/blk-core.c +++ linux-2.6/block/blk-core.c @@ -499,7 +499,7 @@ 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; + (vm_max_readahead * 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"; Index: linux-2.6/fs/fuse/inode.c =================================================================== --- linux-2.6.orig/fs/fuse/inode.c +++ linux-2.6/fs/fuse/inode.c @@ -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 = (vm_max_readahead * 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; Index: linux-2.6/include/linux/mm.h =================================================================== --- linux-2.6.orig/include/linux/mm.h +++ linux-2.6/include/linux/mm.h @@ -1188,7 +1188,11 @@ 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 INITIAL_VM_MAX_READAHEAD 128 /* kbytes */ +extern unsigned long vm_max_readahead; + +int sysctl_vm_max_readahead_handler(struct ctl_table *, int, + void __user *, size_t *, loff_t *); int force_page_cache_readahead(struct address_space *mapping, struct file *filp, pgoff_t offset, unsigned long nr_to_read); Index: linux-2.6/mm/backing-dev.c =================================================================== --- linux-2.6.orig/mm/backing-dev.c +++ linux-2.6/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 = INITIAL_VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE, .state = 0, .capabilities = BDI_CAP_MAP_COPY, .unplug_io_fn = default_unplug_io_fn, Index: linux-2.6/mm/readahead.c =================================================================== --- linux-2.6.orig/mm/readahead.c +++ linux-2.6/mm/readahead.c @@ -17,6 +17,19 @@ #include #include +unsigned long vm_max_readahead = INITIAL_VM_MAX_READAHEAD; + +int sysctl_vm_max_readahead_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *length, loff_t *ppos) +{ + proc_doulongvec_minmax(table, write, buffer, length, ppos); + + default_backing_dev_info.ra_pages = + vm_max_readahead >> (PAGE_CACHE_SHIFT - 10); + + return 0; +} + /* * Initialise a struct file's readahead state. Assumes that the caller has * memset *ra to zero. Index: linux-2.6/kernel/sysctl.c =================================================================== --- linux-2.6.orig/kernel/sysctl.c +++ linux-2.6/kernel/sysctl.c @@ -1273,7 +1273,13 @@ static struct ctl_table vm_table[] = { .extra2 = &one, }, #endif - + { + .procname = "max_readahead_kb", + .data = &vm_max_readahead, + .maxlen = sizeof(vm_max_readahead), + .mode = 0644, + .proc_handler = sysctl_vm_max_readahead_handler, + }, { } }; Index: linux-2.6/Documentation/sysctl/vm.txt =================================================================== --- linux-2.6.orig/Documentation/sysctl/vm.txt +++ linux-2.6/Documentation/sysctl/vm.txt @@ -31,6 +31,7 @@ Currently, these files are in /proc/sys/ - laptop_mode - legacy_va_layout - lowmem_reserve_ratio +- max_readahead_kb - max_map_count - memory_failure_early_kill - memory_failure_recovery @@ -263,6 +264,12 @@ The minimum value is 1 (1/1 -> 100%). ============================================================== +max_readahead_kb: + +This file contains the default maximum readahead that would be used. + +============================================================== + max_map_count: This file contains the maximum number of memory map areas a process -- 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/