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=unavailable 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 13209C33CB2 for ; Fri, 31 Jan 2020 13:01:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DDD22214D8 for ; Fri, 31 Jan 2020 13:01:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="nRpXut7V" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728556AbgAaNBp (ORCPT ); Fri, 31 Jan 2020 08:01:45 -0500 Received: from mail-lj1-f193.google.com ([209.85.208.193]:33770 "EHLO mail-lj1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728514AbgAaNBo (ORCPT ); Fri, 31 Jan 2020 08:01:44 -0500 Received: by mail-lj1-f193.google.com with SMTP id y6so7032995lji.0; Fri, 31 Jan 2020 05:01:43 -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=91NDgBxMOUQX+FZ1BTJVVc6qCU+Cj8++hqqh0GnmSfM=; b=nRpXut7VNzzYjKTPl/iBVkARA1nKKVM2JLhHDU6YEEmxvCw+80Dwl5xODlKBFKjHAB CUsx1vVxYWyG2VTJdeKVLBCPn2qEv8o2mOlJMAiTPMpOUjxTTYJGf4g7DlsoIDZb1dKh e9ybWVTkHB2JKVFao2EeOL/eKD1voyl6aCIVgdgQepoBkXqVrhlzZIZM6zcN8LBWqa/L fRV9PdIdhm+jfSSWv2niorSh3N0IxpcUt0Zu/lham/DwECpLPVGT5fjTgnW3lxp9AhuS bCz7c1d0EyDiPLUu5iEoymetjYYbhwNFRsbq1T6ntHgBt1bLeH0roMA97LCS7QhJmTH3 F4cw== 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=91NDgBxMOUQX+FZ1BTJVVc6qCU+Cj8++hqqh0GnmSfM=; b=H8PVV6C4cNc+LmFxrLtdcZ74VVbBpvQMxe+Nt3d/I/Zcvc1VHBwZuXEEvCKPtf3BFr /1M4XA56LSO70MGIOMBaS1z5fDboNg4pQToZ6YW8r3wOQNo+sIQHtjluXahaPd2BJge9 0KNb8xVQjf42QCj8ygmiM95yBjjRAFRLlw/EXm2HttKANH8PYo9LnaVUmX/es5l7RIOF PheL/59aaUhQF4KalSguAEGcxKLzLBx+OpMujXcApVZjkkEX1YTFWbZBMJGUk20j6k62 fDo4yNNcrZy1R7cWNnEZXcgB4Gu0jnSu/xSrLQroP4gd/U15F2b3YqIGbZcsAi9+U/DW lWsg== X-Gm-Message-State: APjAAAV6NKmWU1PGhXfXG/2UpQa0Oc10QC49Xi/+ol+4oIDqiihW15L4 DFT9gLjU80XaUu8PcxyoRcmWl9G55fs= X-Google-Smtp-Source: APXvYqxa6ny9Hj92Ow3m4QBwi5HVWBuTJM/cFloRyJixABbPoSnn/IRUdm7Q0Xpdu2uwPGjHzHXNgg== X-Received: by 2002:a2e:9e03:: with SMTP id e3mr5870631ljk.186.1580475702053; Fri, 31 Jan 2020 05:01:42 -0800 (PST) Received: from [172.31.190.83] ([86.57.146.226]) by smtp.gmail.com with ESMTPSA id w71sm5430896lff.0.2020.01.31.05.01.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 31 Jan 2020 05:01:41 -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> Message-ID: <14929e52-9437-e856-7eff-4e5b45968f89@gmail.com> Date: Fri, 31 Jan 2020 16:01:40 +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: <5328b35d948ea2a3aa5df2b1d740c7cb1f38c846.1579224594.git.asml.silence@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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 > > 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