From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932332AbdJWP3G (ORCPT ); Mon, 23 Oct 2017 11:29:06 -0400 Received: from mga02.intel.com ([134.134.136.20]:5712 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751260AbdJWP3F (ORCPT ); Mon, 23 Oct 2017 11:29:05 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.43,423,1503385200"; d="scan'208";a="1028304188" From: Kemi Wang To: Jan Kara , Jens Axboe , Darrick J Wong , Kemi Wang , Eric Biggers , Andreas Gruenbacher , Jeff Layton Cc: Dave , Andi Kleen , Tim Chen , Ying Huang , Aaron Lu , Linux Kernel Subject: [PATCH] buffer: Avoid setting buffer bits that are already set Date: Mon, 23 Oct 2017 23:27:24 +0800 Message-Id: <1508772444-27879-1-git-send-email-kemi.wang@intel.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It's expensive to set buffer flags that are already set, because that causes a costly cache line transition. A common case is setting the "verified" flag during ext4 writes. This patch checks for the flag being set first. With the AIM7/creat-clo benchmark testing on a 48G ramdisk based-on ext4 file system, we see 3.3%(15431->15936) improvement of aim7.jobs-per-min on a 2-sockets broadwell platform. What the benchmark does is: it forks 3000 processes, and each process do the following: a) open a new file b) close the file c) delete the file until loop=100*1000 times. The original patch is contributed by Andi Kleen. Signed-off-by: Andi Kleen Signed-off-by: Kemi Wang Tested-by: Kemi Wang --- include/linux/buffer_head.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index c8dae55..e1799f7 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -84,7 +84,8 @@ struct buffer_head { #define BUFFER_FNS(bit, name) \ static __always_inline void set_buffer_##name(struct buffer_head *bh) \ { \ - set_bit(BH_##bit, &(bh)->b_state); \ + if (!test_bit(BH_##bit, &(bh)->b_state)) \ + set_bit(BH_##bit, &(bh)->b_state); \ } \ static __always_inline void clear_buffer_##name(struct buffer_head *bh) \ { \ -- 2.7.4