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=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 43DC3C433E6 for ; Wed, 24 Feb 2021 05:28:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F256D64DDC for ; Wed, 24 Feb 2021 05:28:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233942AbhBXF23 (ORCPT ); Wed, 24 Feb 2021 00:28:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52514 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233806AbhBXF21 (ORCPT ); Wed, 24 Feb 2021 00:28:27 -0500 Received: from mail-qk1-x736.google.com (mail-qk1-x736.google.com [IPv6:2607:f8b0:4864:20::736]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09C71C061574; Tue, 23 Feb 2021 21:27:47 -0800 (PST) Received: by mail-qk1-x736.google.com with SMTP id q85so1118520qke.8; Tue, 23 Feb 2021 21:27:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=aw/UR5s2IwQPzSQ407eWj98h5EXFMZRfL8iJNo841y4=; b=Zo/TLZUriQC1JcSj0ZK1KudC5T/rV0z51TalrrECdksS/wvnLachxYf/kEUxQ1jIZv veZQlyebujp5Rz3SR8SGVZAAxW3kps1Mmk8qG8C/Xyxg8G56/U/PkZqGesNyr219j2Uk e/DiuwDcAGKcgvKNXcsc+EewxzAMpmelOD5PQeIaIxPWW2IOmhd3fqvF4JYS/IkXrKME 02ZrR5GCJWsQ4/7Bn0mF3Bh8q5N/mIb693SpgDTNzE/KZnpcZgF++y9CPCPUCqx2ShF8 +ipDvNuim7jAGitwzsslxHE0pwhiVdeOuNRHTjkcYaA5gm2oEbgB5f5hZO2xMOhHyBmt T50g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=aw/UR5s2IwQPzSQ407eWj98h5EXFMZRfL8iJNo841y4=; b=Glps2qBM3yuM2KoFSTG/u/FmvVdOiJLajZorJ90ZLKRdvTlKt8cFW/C/Mcg3+CCsUJ tpfSjK8CzopOcl4eDKoDG/CQD5UDJoG+sOd5ccz4xqfN120q0ccz5ZvMqHEyNTjqxBKu l93QbSgQ7l8CwKTOPhm6lGiUikcpjuVGERTTz/MJ91gstgKp6g6/Vu0oVAel369pANuj 5bRCUH7ZyZkQ9Kno0JrKu7hBbtWu7sYeIH49XBTqKYsa+9r9js/beKwTTTXHaiyub3Xe vqFlY+FWpjwSIgSvb5uX4eyTZjBsIBA56szDPAynzXUpgbQwcymqAMWZLans00E3wajs fUOA== X-Gm-Message-State: AOAM5320ntTvgYqlFAM0QjXMccNI8XXPLHX80EKCXjSyXebd+l/v6vd0 GWCC2yVvrii97lZfYZ8HnvI= X-Google-Smtp-Source: ABdhPJx39bkgG69E4mrnlUr3nUMK+9eV9c6HxdyY8sMqYv6jTsxP9WRvHfhPzPoeMF1fdlClPjsefA== X-Received: by 2002:a37:a654:: with SMTP id p81mr29167625qke.354.1614144466099; Tue, 23 Feb 2021 21:27:46 -0800 (PST) Received: from localhost (d27-96-190-162.evv.wideopenwest.com. [96.27.162.190]) by smtp.gmail.com with ESMTPSA id r17sm620719qta.78.2021.02.23.21.27.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Feb 2021 21:27:45 -0800 (PST) Date: Tue, 23 Feb 2021 21:27:44 -0800 From: Yury Norov To: Will Deacon Cc: Catalin Marinas , linux-arm-kernel@lists.infradead.org, Linux Kernel Mailing List , linux-arch@vger.kernel.org, Alexey Klimov Subject: Re: [PATCH] arm64: enable GENERIC_FIND_FIRST_BIT Message-ID: <20210224052744.GA1168363@yury-ThinkPad> References: <20201205165406.108990-1-yury.norov@gmail.com> <20201207112530.GB4379@willie-the-truck> <20201208103549.GA5887@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201208103549.GA5887@willie-the-truck> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 08, 2020 at 10:35:50AM +0000, Will Deacon wrote: > On Mon, Dec 07, 2020 at 05:59:16PM -0800, Yury Norov wrote: > > (CC: Alexey Klimov) > > > > On Mon, Dec 7, 2020 at 3:25 AM Will Deacon wrote: > > > > > > On Sat, Dec 05, 2020 at 08:54:06AM -0800, Yury Norov wrote: > > > > ARM64 doesn't implement find_first_{zero}_bit in arch code and doesn't > > > > enable it in config. It leads to using find_next_bit() which is less > > > > efficient: > > > > > > [...] > > > > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > > index 1515f6f153a0..2b90ef1f548e 100644 > > > > --- a/arch/arm64/Kconfig > > > > +++ b/arch/arm64/Kconfig > > > > @@ -106,6 +106,7 @@ config ARM64 > > > > select GENERIC_CPU_AUTOPROBE > > > > select GENERIC_CPU_VULNERABILITIES > > > > select GENERIC_EARLY_IOREMAP > > > > + select GENERIC_FIND_FIRST_BIT > > > > > > Does this actually make any measurable difference? The disassembly with > > > or without this is _very_ similar for me (clang 11). > > > > > > Will > > > > On A-53 find_first_bit() is almost twice faster than find_next_bit(), > > according to > > lib/find_bit_benchmark. (Thanks to Alexey for testing.) > > I guess it's more compiler dependent than anything else, and it's a pity > that find_next_bit() isn't implemented in terms of the generic > find_first_bit() tbh, but if the numbers are as you suggest then I don't > have a problem selecting this on arm64. Ping? 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[96.27.162.190]) by smtp.gmail.com with ESMTPSA id r17sm620719qta.78.2021.02.23.21.27.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Feb 2021 21:27:45 -0800 (PST) Date: Tue, 23 Feb 2021 21:27:44 -0800 From: Yury Norov To: Will Deacon Subject: Re: [PATCH] arm64: enable GENERIC_FIND_FIRST_BIT Message-ID: <20210224052744.GA1168363@yury-ThinkPad> References: <20201205165406.108990-1-yury.norov@gmail.com> <20201207112530.GB4379@willie-the-truck> <20201208103549.GA5887@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201208103549.GA5887@willie-the-truck> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210224_002750_428781_CA091C42 X-CRM114-Status: GOOD ( 23.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Catalin Marinas , Alexey Klimov , Linux Kernel Mailing List , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Dec 08, 2020 at 10:35:50AM +0000, Will Deacon wrote: > On Mon, Dec 07, 2020 at 05:59:16PM -0800, Yury Norov wrote: > > (CC: Alexey Klimov) > > > > On Mon, Dec 7, 2020 at 3:25 AM Will Deacon wrote: > > > > > > On Sat, Dec 05, 2020 at 08:54:06AM -0800, Yury Norov wrote: > > > > ARM64 doesn't implement find_first_{zero}_bit in arch code and doesn't > > > > enable it in config. It leads to using find_next_bit() which is less > > > > efficient: > > > > > > [...] > > > > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > > > index 1515f6f153a0..2b90ef1f548e 100644 > > > > --- a/arch/arm64/Kconfig > > > > +++ b/arch/arm64/Kconfig > > > > @@ -106,6 +106,7 @@ config ARM64 > > > > select GENERIC_CPU_AUTOPROBE > > > > select GENERIC_CPU_VULNERABILITIES > > > > select GENERIC_EARLY_IOREMAP > > > > + select GENERIC_FIND_FIRST_BIT > > > > > > Does this actually make any measurable difference? The disassembly with > > > or without this is _very_ similar for me (clang 11). > > > > > > Will > > > > On A-53 find_first_bit() is almost twice faster than find_next_bit(), > > according to > > lib/find_bit_benchmark. (Thanks to Alexey for testing.) > > I guess it's more compiler dependent than anything else, and it's a pity > that find_next_bit() isn't implemented in terms of the generic > find_first_bit() tbh, but if the numbers are as you suggest then I don't > have a problem selecting this on arm64. Ping? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel