From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751675AbeBBIJr (ORCPT ); Fri, 2 Feb 2018 03:09:47 -0500 Received: from mga05.intel.com ([192.55.52.43]:19240 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750795AbeBBIJj (ORCPT ); Fri, 2 Feb 2018 03:09:39 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.46,447,1511856000"; d="scan'208";a="27483279" Subject: Re: [PATCH v2] buffer: Avoid setting buffer bits that are already set From: kemi To: Jan Kara , Jens Axboe , Darrick J Wong , Eric Biggers , Andreas Gruenbacher , Jeff Layton Cc: Dave , Andi Kleen , Tim Chen , Ying Huang , linux-block , Linux Kernel References: <1508807802-9691-1-git-send-email-kemi.wang@intel.com> Message-ID: <6e946728-23f5-d5df-c8d0-c9ec4251557c@intel.com> Date: Fri, 2 Feb 2018 16:07:28 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Jens Could you help to merge this patch to your tree? Thanks On 2017年11月03日 10:29, kemi wrote: > > > On 2017年10月24日 09:16, Kemi Wang wrote: >> 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 >> Reviewed-by: Jens Axboe >> --- > > Seems that this patch is still not merged. Anything wrong with that? thanks > >> include/linux/buffer_head.h | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h >> index c8dae55..211d8f5 100644 >> --- a/include/linux/buffer_head.h >> +++ b/include/linux/buffer_head.h >> @@ -80,11 +80,14 @@ struct buffer_head { >> /* >> * macro tricks to expand the set_buffer_foo(), clear_buffer_foo() >> * and buffer_foo() functions. >> + * To avoid reset buffer flags that are already set, because that causes >> + * a costly cache line transition, check the flag first. >> */ >> #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) \ >> { \ >>