Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932701AbWEXLUG (ORCPT ); Wed, 24 May 2006 07:20:06 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932687AbWEXLT4 (ORCPT ); Wed, 24 May 2006 07:19:56 -0400 Received: from smtp.ustc.edu.cn ([202.38.64.16]:45441 "HELO ustc.edu.cn") by vger.kernel.org with SMTP id S932701AbWEXLTJ (ORCPT ); Wed, 24 May 2006 07:19:09 -0400 Message-ID: <348469546.16482@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Message-Id: <20060524111907.134685550@localhost.localdomain> References: <20060524111246.420010595@localhost.localdomain> Date: Wed, 24 May 2006 19:13:06 +0800 From: Wu Fengguang To: Andrew Morton Cc: linux-kernel@vger.kernel.org, Wu Fengguang Subject: [PATCH 20/33] readahead: initial method - expected read size Content-Disposition: inline; filename=readahead-method-initial-size-expect.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3629 Lines: 117 backing_dev_info.ra_expect_bytes is dynamicly updated to be the expected read pages on start-of-file. It allows the initial readahead to be more aggressive and hence efficient. Signed-off-by: Wu Fengguang --- fs/file_table.c | 7 ++++++ include/linux/mm.h | 1 mm/readahead.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 63 insertions(+) --- linux-2.6.17-rc4-mm3.orig/include/linux/mm.h +++ linux-2.6.17-rc4-mm3/include/linux/mm.h @@ -1032,6 +1032,7 @@ unsigned long page_cache_readahead(struc void handle_ra_miss(struct address_space *mapping, struct file_ra_state *ra, pgoff_t offset); unsigned long max_sane_readahead(unsigned long nr); +void fastcall readahead_close(struct file *file); #ifdef CONFIG_ADAPTIVE_READAHEAD extern int readahead_ratio; --- linux-2.6.17-rc4-mm3.orig/fs/file_table.c +++ linux-2.6.17-rc4-mm3/fs/file_table.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -160,6 +161,12 @@ void fastcall __fput(struct file *file) might_sleep(); fsnotify_close(file); + +#ifdef CONFIG_ADAPTIVE_READAHEAD + if (file->f_ra.flags & RA_FLAG_EOF) + readahead_close(file); +#endif + /* * The function eventpoll_release() should be the first called * in the file cleanup chain. --- linux-2.6.17-rc4-mm3.orig/mm/readahead.c +++ linux-2.6.17-rc4-mm3/mm/readahead.c @@ -1555,6 +1555,61 @@ static inline void get_readahead_bounds( PAGES_KB(128)), *ra_max / 2); } +/* + * When closing a normal readonly file, + * - on cache hit: increase `backing_dev_info.ra_expect_bytes' slowly; + * - on cache miss: decrease it rapidly. + * + * The resulted `ra_expect_bytes' answers the question of: + * How many pages are expected to be read on start-of-file? + */ +void fastcall readahead_close(struct file *file) +{ + struct inode *inode = file->f_dentry->d_inode; + struct address_space *mapping = inode->i_mapping; + struct backing_dev_info *bdi = mapping->backing_dev_info; + unsigned long pos = file->f_pos; + unsigned long pgrahit = file->f_ra.cache_hits; + unsigned long pgaccess = 1 + pos / PAGE_CACHE_SIZE; + unsigned long pgcached = mapping->nrpages; + + if (!pos) /* pread */ + return; + + if (pgcached > bdi->ra_pages0) /* excessive reads */ + return; + + if (pgaccess >= pgcached) { + if (bdi->ra_expect_bytes < bdi->ra_pages0 * PAGE_CACHE_SIZE) + bdi->ra_expect_bytes += pgcached * PAGE_CACHE_SIZE / 8; + + debug_inc(initial_ra_hit); + dprintk("initial_ra_hit on file %s size %lluK " + "pos %lu by %s(%d)\n", + file->f_dentry->d_name.name, + i_size_read(inode) / 1024, + pos, + current->comm, current->pid); + } else { + unsigned long missed; + + missed = (pgcached - pgaccess) * PAGE_CACHE_SIZE; + if (bdi->ra_expect_bytes >= missed / 2) + bdi->ra_expect_bytes -= missed / 2; + + debug_inc(initial_ra_miss); + dprintk("initial_ra_miss on file %s " + "size %lluK cached %luK hit %luK " + "pos %lu by %s(%d)\n", + file->f_dentry->d_name.name, + i_size_read(inode) / 1024, + pgcached << (PAGE_CACHE_SHIFT - 10), + pgrahit << (PAGE_CACHE_SHIFT - 10), + pos, + current->comm, current->pid); + } +} + #endif /* CONFIG_ADAPTIVE_READAHEAD */ /* -- - 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/