From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABE03C2BA83 for ; Wed, 12 Feb 2020 12:57:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A43720714 for ; Wed, 12 Feb 2020 12:57:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IyduzuDP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727933AbgBLM5L (ORCPT ); Wed, 12 Feb 2020 07:57:11 -0500 Received: from mail-lj1-f195.google.com ([209.85.208.195]:38902 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727665AbgBLM5L (ORCPT ); Wed, 12 Feb 2020 07:57:11 -0500 Received: by mail-lj1-f195.google.com with SMTP id w1so2194365ljh.5; Wed, 12 Feb 2020 04:57:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:from:to:references:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=FuSs9kS8ae3w5JjTuFnQ+TphT7r0wrypfGkdXwpwO3k=; b=IyduzuDPBYv3bttdle4/H2G/Mobjrt2pHYyuCTdRgF3Nxm7H6tBfoondtSVigiw6Tl f3V36pAg8zbGds845Zknr0bzJ2lh1g3Bf/Qg66A906mOxWKAxK3Z0E0rK7/djP/Av5Lr c+tmAjcG5IwBgwN4T+eZ6sxwv/AMsxjgUH0XD7aYonE156L/xGbtPujYtu+ZTMEhRYZn H7f8aq6sAewK9W/QZbKyBGBf4aJLa39q5XAcSbqLPxeH1b8xhQdjdn4S1MikK3d4xKEd Ot+5p8Hkm5DAOiqjVaRwohUuSuPhLXOi2riiZl1CYkJlOfhie2k2D4kIw3lPbr37QKmP Vulw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:from:to:references:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=FuSs9kS8ae3w5JjTuFnQ+TphT7r0wrypfGkdXwpwO3k=; b=Ttyqeu29dGR7H/wz+C/TBV1tJXOC3wzExSJlzOouY+B7ZkB1b4EIkRX/eEAz8DheWb uUTeAnzgnfzGG/qeSgqwSgCT8N1ieSUm7l0jEdFNFWYcpbRKdsvDqw5qcDNs61GX3UKK Ti5mT8PF1WfGUrkU4WRDWriD71pyQBa3/Cr8f7uQMmtrUxPK2AbJlMijtmQT4X6iHust tsjGugfG89BDrr5+cA6EfJsM5p+dXoEACx8XXNNKqm3F0ObhR4QkYHXlKYRFa4WbTAv6 D7Djqrp4sAXvjH78H79Nf4To2jiGiuOKb1EpyPaC500MQyUv3P5Yb9i71PjJIAl7WK8O paLw== X-Gm-Message-State: APjAAAV3BqQbRTilWQ4hL0u+UWef22LfKDcnLmSxQ5d2IECS516quNqB k3F+UIufCGaUvp5hzJM1BmqidKgNbds= X-Google-Smtp-Source: APXvYqxcw6Qgtiyx0LP+B0IJNtbp/9B9kOUrcgrqm5D7yiJFSUFGSOQXha2tKnmxxWuj4+YkHDI5Kw== X-Received: by 2002:a2e:96c4:: with SMTP id d4mr7873560ljj.225.1581512228434; Wed, 12 Feb 2020 04:57:08 -0800 (PST) Received: from [172.31.190.83] ([86.57.146.226]) by smtp.gmail.com with ESMTPSA id t1sm226977lji.98.2020.02.12.04.57.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Feb 2020 04:57:04 -0800 (PST) Subject: Re: [PATCH v2] fs: optimise kiocb_set_rw_flags() From: Pavel Begunkov To: Alexander Viro , willy@infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <8cecd243-38aa-292d-15cd-49b485f9253f@gmail.com> <5328b35d948ea2a3aa5df2b1d740c7cb1f38c846.1579224594.git.asml.silence@gmail.com> <14929e52-9437-e856-7eff-4e5b45968f89@gmail.com> Message-ID: <3fd1844b-d059-7729-8d09-ad51d11514fa@gmail.com> Date: Wed, 12 Feb 2020 15:57:03 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <14929e52-9437-e856-7eff-4e5b45968f89@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/31/2020 4:01 PM, Pavel Begunkov wrote: > On 1/17/2020 4:32 AM, Pavel Begunkov wrote: >> kiocb_set_rw_flags() generates a poor code with several memory writes >> and a lot of jumps. Help compilers to optimise it. >> >> Tested with gcc 9.2 on x64-86, and as a result, it its output now is a >> plain code without jumps accumulating in a register before a memory >> write. > > Humble ping Anyone? > >> >> Signed-off-by: Pavel Begunkov >> --- >> >> v2: check for 0 flags in advance (Matthew Wilcox) >> >> include/linux/fs.h | 16 +++++++++++----- >> 1 file changed, 11 insertions(+), 5 deletions(-) >> >> diff --git a/include/linux/fs.h b/include/linux/fs.h >> index 98e0349adb52..22b46fc8fdfa 100644 >> --- a/include/linux/fs.h >> +++ b/include/linux/fs.h >> @@ -3402,22 +3402,28 @@ static inline int iocb_flags(struct file *file) >> >> static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags) >> { >> + int kiocb_flags = 0; >> + >> + if (!flags) >> + return 0; >> if (unlikely(flags & ~RWF_SUPPORTED)) >> return -EOPNOTSUPP; >> >> if (flags & RWF_NOWAIT) { >> if (!(ki->ki_filp->f_mode & FMODE_NOWAIT)) >> return -EOPNOTSUPP; >> - ki->ki_flags |= IOCB_NOWAIT; >> + kiocb_flags |= IOCB_NOWAIT; >> } >> if (flags & RWF_HIPRI) >> - ki->ki_flags |= IOCB_HIPRI; >> + kiocb_flags |= IOCB_HIPRI; >> if (flags & RWF_DSYNC) >> - ki->ki_flags |= IOCB_DSYNC; >> + kiocb_flags |= IOCB_DSYNC; >> if (flags & RWF_SYNC) >> - ki->ki_flags |= (IOCB_DSYNC | IOCB_SYNC); >> + kiocb_flags |= (IOCB_DSYNC | IOCB_SYNC); >> if (flags & RWF_APPEND) >> - ki->ki_flags |= IOCB_APPEND; >> + kiocb_flags |= IOCB_APPEND; >> + >> + ki->ki_flags |= kiocb_flags; >> return 0; >> } >> >> > -- Pavel Begunkov