From owner-svn-src-head@freebsd.org Sat May 5 16:14:40 2018 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 1A6B1FB2465; Sat, 5 May 2018 16:14:40 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: from mail-qk0-x242.google.com (mail-qk0-x242.google.com [IPv6:2607:f8b0:400d:c09::242]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id A183168FBC; Sat, 5 May 2018 16:14:39 +0000 (UTC) (envelope-from mjguzik@gmail.com) Received: by mail-qk0-x242.google.com with SMTP id a202so18955555qkg.3; Sat, 05 May 2018 09:14:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=ZHpw9VLX3+uMNAuqU4Bzl5HZUBhwx2C2Ij4CZV2Fsak=; b=bKKxpwEBVIIpyrw8L00yEsUZx/6qCiwYNP1P4T7ufKOurFCnVe97qeiAAyVsoRvn9T Gy+53iX6vQrSVd8LBX+xEVd38bRgninRbnmduvwIeZYhcJ34sQ/AxTE2UDMxcd14BIXJ mPZO+v8JdF3HgY9jFSHxgjNoQkMjQUwuDQkcB0iybNwzQD/lWZ+DLsLKY9Jg+RZd4Qtj vb0uKJdNtSWb6WLe5BwpbiBH6Qfx5oRdSzeyzw6WuJSmxRR2AMq5wJvekMpWWBuzYY7J 2aAc/Ly3HXLLu0O3RzH9x4Tfuz60xAjMg7bZ/okglXEEalNUDN6QZYG+SpiMa0w8EL6g +mUA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=ZHpw9VLX3+uMNAuqU4Bzl5HZUBhwx2C2Ij4CZV2Fsak=; b=baug3NpH60/MKNBasH/jWJDD1k16jtZgXxFV/FkOutGL+iYcakTqP9hijxQA5aDruI WqEpuLIu88YWcEt1wxjnxZfUMvyhjRmLj8dnjdw73untODybRj0d4ywon2LF+pNTmE59 EWgbCNmUVWOxocDxS2MIv3EQX14YMUsc/E/0PgClTVkwbnLO8U9SjZrtQcbPoCLllAjj UZKdK9GDsCUMXpbsHaowqlDMyKrcr1RqjhXlUJDEIMwsJDmUXDST3euO9Dz1BKzxhNlR +JsZx5UrFNZAtNxX9FMygS1PqSdZwT9DLJqlDBXmE6Ikd3e7ikeVpNZgXHfHU9ucTc+E xxTA== X-Gm-Message-State: ALQs6tC2Bj7Cbr+RXfHRhnGaMEFZOFSYn0qZilPKIQdW3xHd1hGnNCbR DTrHWhYZSxuvxG5fG5/wVJlDwQ/6RV/HWweExU0= X-Google-Smtp-Source: AB8JxZqAvAe2XnaDnKsA/6WQLtJKl+qL7jGbBny/RIqBm03w+W8eOJAyQ012k/v0Tk0wMPFLw7lF7e5VEkmt90jsgqQ= X-Received: by 10.55.147.66 with SMTP id v63mr27033272qkd.40.1525536878900; Sat, 05 May 2018 09:14:38 -0700 (PDT) MIME-Version: 1.0 Received: by 10.200.28.74 with HTTP; Sat, 5 May 2018 09:14:38 -0700 (PDT) In-Reply-To: <20180505120055.GA81833@FreeBSD.org> References: <201805040400.w4440moH025057@repo.freebsd.org> <20180504155301.GA56280@spindle.one-eyed-alien.net> <20180505090954.X1307@besplex.bde.org> <20180505120055.GA81833@FreeBSD.org> From: Mateusz Guzik Date: Sat, 5 May 2018 18:14:38 +0200 Message-ID: Subject: Re: svn commit: r333240 - in head/sys: powerpc/powerpc sys To: Alexey Dokuchaev Cc: Bruce Evans , Conrad Meyer , svn-src-head@freebsd.org, svn-src-all@freebsd.org, Brooks Davis , src-committers Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.25 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 05 May 2018 16:14:40 -0000 On Sat, May 5, 2018 at 2:00 PM, Alexey Dokuchaev wrote: > On Sat, May 05, 2018 at 10:38:29AM +1000, Bruce Evans wrote: > > ... > > Summary: this change wouldn't have passed my review. I have used similar > > changes for 15-20 years but never made them production quality since > there > > are too many variations to consider and testing showed insignificant > > improvements except for micro-benchmarks. > > Perhaps Foundation could sponsor your work to make them production quality > Bruce. :-) > > Seriously though, I'm a bit worried to see these commits happening at the > same time correctness of the implementation is still under discussion and > disputes. Shall I expect that after my next -CURRENT update things would > suddenly stop working? [1] > > ./danfe > > [1] https://bugzilla.redhat.com/show_bug.cgi?id=638477 > > Nothing of the sort was done here. They had a memcpy function which internally behaved like memmove. They changed to behave like mere memcpy (i.e. assume non-overlapping buffers). This caused buggy code to run into trouble. bcopy has memmove semantics and this change keeps that. The only difference is that instead of always generating a call, the compiler is allowed to perform the copy in place in certain cases. This is precisely what happens almost everywhere and it was not happening in the kernel because of a giant hammer -fno-builtin flag (added to reduce changes the compiler will do stuff the kernel does not want to deal with). -- Mateusz Guzik