From owner-svn-src-head@freebsd.org Fri May 4 23:44:50 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 92DD9FBBCE6 for ; Fri, 4 May 2018 23:44:50 +0000 (UTC) (envelope-from juli@northcloak.com) Received: from mail-qt0-x22d.google.com (mail-qt0-x22d.google.com [IPv6:2607:f8b0:400d:c0d::22d]) (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 2E9006E5D5 for ; Fri, 4 May 2018 23:44:49 +0000 (UTC) (envelope-from juli@northcloak.com) Received: by mail-qt0-x22d.google.com with SMTP id m9-v6so8824116qtb.5 for ; Fri, 04 May 2018 16:44:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=northcloak-com.20150623.gappssmtp.com; s=20150623; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=aaP2NRbHR2gjVqG9rFDivwEQtTQ+WTm9lT/VmdPuCQA=; b=nSaP31APHUmjzt1juCQP36cqM4UX05aUGzFST7wgnmkySfzxNOhgIW+9dr/3psEaDX XZN2veWrP3BGdAdTO3HdFAq9+MuO5USfLvMCkt5rKNOojOhBhCMCGgFE+eKoIMVTZA9u o6zdYCujKsNLhM3ync1XLBonRFGGAaU9CkEyWnCDo8sxUmpTLW6HWS8oIpq5ZD7gsFlZ 2YinMLMH2fJRFFSjbZyV6VCuw0xDiK1hA2QNt8PA1N4V+lINwrXrL2Jx9J3ppGjG+R0y r79ZGYO7p6da4EkDHlWsC/j1Pn317KjlkshG8u1mGlnXMJXDliXFjutI9P3blhXc5Qpt h7Og== 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=aaP2NRbHR2gjVqG9rFDivwEQtTQ+WTm9lT/VmdPuCQA=; b=B6t1ehqORU4dV13beOjhCvKDBdnLkVs81a20+38T8JERITmzmeUYO6z1FZ22E7NU3J acOraY+woS+dIxrJt544h3qt9UJWVMfdqLznuoQE7yYyDy8KgFHsRNZ0EliYqG8kTTPa zS50QgcCpyF68BupYUqivuU+paV7dMuuwzpsUWOUt28UDTWq7D/R28cRTgkt8I+hwIIP 550O6Bg3skz2Ei1wATJsvr/Zo7eCjEhfv2s0ZvZT4uti6rTzSzcNtpToQDpJjDiAz2r8 NitjMDAcDIwdZills9YgyimM5qQnf5fkXwSBsmiPQtZ19EyI02wj2mcpCiEXsMgWVCW7 FiXQ== X-Gm-Message-State: ALQs6tAPLNwjFl3CG8r/3g7Aj+XNKroRr1NVE0TLMY88ZjMm8B7DvhEQ //UahSz1FkGig0Ypati/7/bZoiAaXmcEDyyjNQ2DXQ== X-Google-Smtp-Source: AB8JxZovzZcmaIXKowLZMca2mLmEpzAf22pkP70bQnyQev5lT1B3mDbCl+j64GCXU76b5V1sF0GZj9rZfQ9JbzamyXA= X-Received: by 2002:aed:23a1:: with SMTP id j30-v6mr15510498qtc.361.1525477489609; Fri, 04 May 2018 16:44:49 -0700 (PDT) MIME-Version: 1.0 Received: by 10.200.69.23 with HTTP; Fri, 4 May 2018 16:44:09 -0700 (PDT) In-Reply-To: References: <201805042241.w44MfC9E090893@repo.freebsd.org> From: Juli Mallett Date: Fri, 4 May 2018 16:44:09 -0700 Message-ID: Subject: Re: svn commit: r333266 - head/sys/amd64/amd64 To: Mateusz Guzik Cc: Steven Hartland , Mateusz Guzik , src-committers , svn-src-all@freebsd.org, svn-src-head@freebsd.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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: Fri, 04 May 2018 23:44:50 -0000 On 4 May 2018 at 16:12, Mateusz Guzik wrote: > On Sat, May 5, 2018 at 12:58 AM, Steven Hartland < > steven.hartland@multiplay.co.uk> wrote: > >> Can we get the why in commit messages please? >> >> This sort of message doesnt provide anything more that can be obtained >> from reading the diff, which just leaves us wondering why? >> >> I=E2=80=99m sure there is a good reason, but without confirmation we=E2= =80=99re just left >> guessing. The knock on to this is if some assumption that caused the why >> changes, anyone looking at this will not be able to make an informed >> descision that that was the case. >> >> > bcopy is an equivalent of memmove, i.e. it accepts overlapping buffers. > But if we know for a fact they don't overlap (like here), doing this over > memcpy (which does not accept such buffers) only puts avoidable > constraints on the optimizer. > > This is a rather pedestrian change which can be made in many places, > I don't see the point of repeating the explanation in each one. Although > I guess it would make sense to point at a specific commit which explains > things. > I feel like the second paragraph in particular suggests a methodical project (maybe in a branch?) to convert or mark all instances as not-to-be-converted based on their context and practical concerns (like performance) might be better than doing a bunch of one-off commits, with batched commits to -CURRENT from time-to-time. Then it's easy to say "Phase IV of bcopy analysis in kernel: convert to memcpy for all non-overlapping small copies" with a whole bunch of changes lumped together= .