From: alex chen Subject: A doubt on journal_async_commit option Date: Fri, 12 Dec 2014 14:03:32 +0800 Message-ID: <548A8534.1050606@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Joseph Qi To: , Jan Kara , Return-path: Received: from szxga01-in.huawei.com ([119.145.14.64]:5268 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751126AbaLLGDy (ORCPT ); Fri, 12 Dec 2014 01:03:54 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: This commit 0e3d2a6313(ext4: Fix async commit mode to be safe by using a barrier) show that using journal_async_commit feature has a 50% performance improvement. But I tested in SUSE Linux Enterprise Server 11 SP3(linux kernel 3.0.93) and Red Hat Enterprise linux 6.4(linux kernel 2.6.32), the result show this feature has no performance improvement. My test command: mount /dev/sdb /mnt/sdb ./fs_mark -d /mnt/sdb/ -s 10240 -n 1000 umount mount /dev/sdb /mnt/sdb -o journal_async_commit ./fs_mark -d /mnt/sdb/ -s 10240 -n 1000 umount My test result: FSUse% Count Size Files/sec App Overhead 6 1000 10240 42.1 10671 vs. -o journal_async_commit FSUse% Count Size Files/sec App Overhead 6 1000 10240 63.9 10625 Superblock info(-o journal_async_commit): Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Block size: 4096 Journal backup: inode blocks Journal features: journal_checksum journal_async_commit Journal size: 128M Journal length: 32768 Journal sequence: 0x000017a6 Journal start: 1 Am I missing something? ---Alex