Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755473AbWKOH4X (ORCPT ); Wed, 15 Nov 2006 02:56:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S966599AbWKOH4J (ORCPT ); Wed, 15 Nov 2006 02:56:09 -0500 Received: from smtp.ustc.edu.cn ([202.38.64.16]:60622 "HELO ustc.edu.cn") by vger.kernel.org with SMTP id S1755478AbWKOHuc (ORCPT ); Wed, 15 Nov 2006 02:50:32 -0500 Message-ID: <363577028.93218@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Message-Id: <20061115075031.909090639@localhost.localdomain> References: <20061115075007.832957580@localhost.localdomain> Date: Wed, 15 Nov 2006 15:50:30 +0800 From: Wu Fengguang To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Wu Fengguang Subject: [PATCH 23/28] readahead: laptop mode Content-Disposition: inline; filename=readahead-laptop-mode.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3434 Lines: 112 When the laptop drive is spinned down, defer look-ahead to spin up time. The implementation employs a poll based method, for performance is not a concern in this code path. The poll interval is 64KB, which should be small enough for movies/musics. The user space application is responsible for proper caching to hide the spin-up-and-read delay. For crazy laptop users who prefer aggressive read-ahead, here is the way: # echo 1000 > /proc/sys/vm/readahead_ratio # blockdev --setra 524280 /dev/hda # this is the max possible value Notes: - It is still an untested feature. - It is safer to use blockdev+fadvise to increase ra-max for a single file, which needs patching your movie player. - Be sure to restore them to sane values in normal operations! Signed-off-by: Wu Fengguang Signed-off-by: Andrew Morton --- linux-2.6.19-rc5-mm2.orig/include/linux/writeback.h +++ linux-2.6.19-rc5-mm2/include/linux/writeback.h @@ -86,6 +86,12 @@ void laptop_io_completion(void); void laptop_sync_completion(void); void throttle_vm_writeout(void); +extern struct timer_list laptop_mode_wb_timer; +static inline int laptop_spinned_down(void) +{ + return !timer_pending(&laptop_mode_wb_timer); +} + /* These are exported to sysctl. */ extern int dirty_background_ratio; extern int vm_dirty_ratio; --- linux-2.6.19-rc5-mm2.orig/mm/page-writeback.c +++ linux-2.6.19-rc5-mm2/mm/page-writeback.c @@ -375,7 +375,7 @@ static void wb_timer_fn(unsigned long un static void laptop_timer_fn(unsigned long unused); static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0); -static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0); +DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0); /* * Periodic writeback of "old" data. --- linux-2.6.19-rc5-mm2.orig/mm/readahead.c +++ linux-2.6.19-rc5-mm2/mm/readahead.c @@ -17,6 +17,7 @@ #include #include #include +#include #include @@ -822,6 +823,32 @@ out: } /* + * Set a new look-ahead mark at @next. + * Return 0 if the new mark is successfully set. + */ +static int renew_lookahead(struct address_space *mapping, + struct file_ra_state *ra, + pgoff_t offset, pgoff_t next) +{ + struct page *page; + + if (offset == ra->lookahead_index && + next >= ra->readahead_index) + return 1; + + if (!(page = find_get_page(mapping, next))) + return 1; + + SetPageReadahead(page); + page_cache_release(page); + + if (ra->lookahead_index == offset) + ra->lookahead_index = next; + + return 0; +} + +/* * Update `backing_dev_info.ra_thrash_bytes' to be a _biased_ average of * read-ahead sizes. Which makes it an a-bit-risky(*) estimation of the * _minimal_ read-ahead thrashing threshold on the device. @@ -1629,6 +1656,15 @@ page_cache_readahead_adaptive(struct add ra_account(ra, RA_EVENT_IO_CONGESTION, req_size); return 0; } + + /* + * Defer read-ahead to save energy. + */ + if (unlikely(laptop_mode && laptop_spinned_down())) { + if (!renew_lookahead(mapping, ra, offset, + offset + LAPTOP_POLL_INTERVAL)) + return 0; + } } if (page) -- - 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/