From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761684AbXGVIYz (ORCPT ); Sun, 22 Jul 2007 04:24:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755957AbXGVIYd (ORCPT ); Sun, 22 Jul 2007 04:24:33 -0400 Received: from brick.kernel.dk ([80.160.20.94]:27067 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753971AbXGVIYa (ORCPT ); Sun, 22 Jul 2007 04:24:30 -0400 Date: Sun, 22 Jul 2007 10:24:34 +0200 From: Jens Axboe To: Peter Zijlstra Cc: linux-kernel , Fengguang Wu , riel , Andrew Morton , Rusty Russell , Tim Pepper , Chris Snook Subject: Re: [PATCH 3/3] readahead: scale max readahead size depending on memory size Message-ID: <20070722082434.GR11657@kernel.dk> References: <20070721210005.000228000@chello.nl> <20070721210052.497469000@chello.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070721210052.497469000@chello.nl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 21 2007, Peter Zijlstra wrote: > Scale the default max readahead size with the system memory size. > > Signed-off-by: Peter Zijlstra > --- > block/ll_rw_blk.c | 2 +- > include/linux/fs.h | 1 + > mm/readahead.c | 32 ++++++++++++++++++++++++++++++++ > 3 files changed, 34 insertions(+), 1 deletion(-) > > Index: linux-2.6/block/ll_rw_blk.c > =================================================================== > --- linux-2.6.orig/block/ll_rw_blk.c > +++ linux-2.6/block/ll_rw_blk.c > @@ -208,7 +208,7 @@ void blk_queue_make_request(request_queu > blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS); > blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS); > q->make_request_fn = mfn; > - q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; > + bdi_ra_init(&q->backing_dev_info); > q->backing_dev_info.state = 0; > q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY; > blk_queue_max_sectors(q, SAFE_MAX_SECTORS); > Index: linux-2.6/include/linux/fs.h > =================================================================== > --- linux-2.6.orig/include/linux/fs.h > +++ linux-2.6/include/linux/fs.h > @@ -1696,6 +1696,7 @@ extern long do_splice_direct(struct file > > extern void > file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping); > +extern void bdi_ra_init(struct backing_dev_info *bdi); > extern loff_t no_llseek(struct file *file, loff_t offset, int origin); > extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin); > extern loff_t remote_llseek(struct file *file, loff_t offset, int origin); > Index: linux-2.6/mm/readahead.c > =================================================================== > --- linux-2.6.orig/mm/readahead.c > +++ linux-2.6/mm/readahead.c > @@ -42,6 +42,38 @@ file_ra_state_init(struct file_ra_state > } > EXPORT_SYMBOL_GPL(file_ra_state_init); > > +static unsigned long ra_pages; > + > +static __init int readahead_init(void) > +{ > + /* > + * Scale the max readahead window with system memory > + * > + * 64M: 128K > + * 128M: 180K > + * 256M: 256K > + * 512M: 360K > + * 1G: 512K > + * 2G: 724K > + * 4G: 1024K > + * 8G: 1448K > + * 16G: 2048K > + */ > + ra_pages = int_sqrt(totalram_pages/16); > + if (ra_pages > (2 << (20 - PAGE_SHIFT))) > + ra_pages = 2 << (20 - PAGE_SHIFT); > + > + return 0; > +} How did you come up with these numbers? -- Jens Axboe