Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754277Ab0BVB3v (ORCPT ); Sun, 21 Feb 2010 20:29:51 -0500 Received: from mga03.intel.com ([143.182.124.21]:4165 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754167Ab0BVB3i (ORCPT ); Sun, 21 Feb 2010 20:29:38 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.49,514,1262592000"; d="scan'208";a="246451060" Date: Sun, 21 Feb 2010 23:52:08 +0800 From: Wu Fengguang To: Nikanth Karthikesan Cc: Dave Chinner , Ankit Jain , Andrew Morton , "balbir@linux.vnet.ibm.com" , Jens Axboe , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Christian Ehrhardt Subject: Re: [PATCH v2] Make VM_MAX_READAHEAD a kernel parameter Message-ID: <20100221155208.GA22319@localhost> References: <201002091659.27037.knikanth@suse.de> <201002111715.04411.knikanth@suse.de> <20100214213724.GA28392@discord.disaster> <201002151006.37294.knikanth@suse.de> <20100221142600.GA10036@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100221142600.GA10036@localhost> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4109 Lines: 120 > +unsigned long max_readahead_pages = VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE; > + > +static int __init readahead(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; > + } > + > + max_readahead_pages = bytes / PAGE_CACHE_SIZE; > + default_backing_dev_info.ra_pages = max_readahead_pages; > + return 0; > +} > + > +early_param("readahead", readahead); This further optimizes away max_readahead_pages :) --- make default readahead size a kernel parameter 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 2010-02-21 22:41:29.000000000 +0800 +++ linux/Documentation/kernel-parameters.txt 2010-02-21 22:41:30.000000000 +0800 @@ -2174,6 +2174,10 @@ 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 2010-02-21 22:41:29.000000000 +0800 +++ linux/block/blk-core.c 2010-02-21 22:41:30.000000000 +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 2010-02-21 22:41:29.000000000 +0800 +++ linux/fs/fuse/inode.c 2010-02-21 22:41:30.000000000 +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 2010-02-21 22:41:29.000000000 +0800 +++ linux/mm/readahead.c 2010-02-21 22:42:15.000000000 +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/