From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sat, 1 Jun 2002 04:39:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sat, 1 Jun 2002 04:39:03 -0400 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:44810 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id ; Sat, 1 Jun 2002 04:38:25 -0400 Message-ID: <3CF888CB.FF93908E@zip.com.au> Date: Sat, 01 Jun 2002 01:41:47 -0700 From: Andrew Morton X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.19-pre9 i686) X-Accept-Language: en MIME-Version: 1.0 To: Linus Torvalds CC: lkml Subject: [patch 5/16] speed up writes Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Speeds up generic_file_write() by not calling mark_inode_dirty() when the mtime and ctime didn't change. There may be concerns over the fact that this restricts mtime and ctime updates to one-second resolution. But the interface doesn't support that anyway - all the filesystem knows is that its dirty_inode() superop was called. It doesn't know why. So filesystems which support high-resolution timestamps already need to make their own arrangements. We need an update_mtime i_op to support those properly. time to write a one megabyte file one-byte-at-a-time: Before: ext3: 24.8 seconds ext2: 4.9 seconds reiserfs: 17.0 seconds After: ext3: 22.5 seconds ext2: 4.8 seconds reiserfs: 11.6 seconds Not much improvement because we're also calling expensive mark_inode_dirty() functions when i_size is expanded. So compare the overwrite case: time dd if=/dev/zero of=foo bs=1 count=1M conv=notrunc ext3 before: 20.0 seconds ext3 after: 9.7 seconds ===================================== --- 2.5.19/mm/filemap.c~mtime-speedup Sat Jun 1 01:18:08 2002 +++ 2.5.19-akpm/mm/filemap.c Sat Jun 1 01:18:08 2002 @@ -2098,6 +2098,7 @@ generic_file_write(struct file *file, co ssize_t written; int err; unsigned bytes; + time_t time_now; if (unlikely((ssize_t) count < 0)) return -EINVAL; @@ -2195,9 +2196,12 @@ generic_file_write(struct file *file, co goto out; remove_suid(file->f_dentry); - inode->i_ctime = CURRENT_TIME; - inode->i_mtime = CURRENT_TIME; - mark_inode_dirty_sync(inode); + time_now = CURRENT_TIME; + if (inode->i_ctime != time_now || inode->i_mtime != time_now) { + inode->i_ctime = time_now; + inode->i_mtime = time_now; + mark_inode_dirty_sync(inode); + } if (unlikely(file->f_flags & O_DIRECT)) { written = generic_file_direct_IO(WRITE, file, -