From mboxrd@z Thu Jan 1 00:00:00 1970 From: Duy Nguyen Subject: Re: Parallel checkout (Was Re: 0 bot for Git) Date: Fri, 15 Apr 2016 18:32:49 +0700 Message-ID: References: <20160415095139.GA3985@lanh> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Cc: Stefan Beller , "git@vger.kernel.org" , Jeff King , Michael Haggerty To: Christian Couder X-From: git-owner@vger.kernel.org Fri Apr 15 13:33:42 2016 Return-path: Envelope-to: gcvg-git-2@plane.gmane.org Received: from vger.kernel.org ([209.132.180.67]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ar20L-0002yd-Gv for gcvg-git-2@plane.gmane.org; Fri, 15 Apr 2016 13:33:41 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751316AbcDOLdi (ORCPT ); Fri, 15 Apr 2016 07:33:38 -0400 Received: from mail-lf0-f42.google.com ([209.85.215.42]:34875 "EHLO mail-lf0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751315AbcDOLdZ (ORCPT ); Fri, 15 Apr 2016 07:33:25 -0400 Received: by mail-lf0-f42.google.com with SMTP id c126so141870494lfb.2 for ; Fri, 15 Apr 2016 04:33:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=8eiUt/6y7NKmN4eQ07N4jPkd9JJGEP9k2tD5IVIlXFI=; b=uZ1iphx1lwSZRYZ9pliOn1eF5SHhluKbo/bkCK+0IKGtQuePV5lqMCCpWojN+xxCcl q9DGTwqx641BYDYcJG9x8aXj5Rb5MiwRpCWAFGnf2IBtrsbZmEwD8r1HUObwXmrC0Qam VBn32xS/RtusgvS2llHvNYFUgQMPOV8o2VakXjRNtE/x6QkkJh2mb1Mg/Ugy+zHwVedX +QysYHTIGg8+X/FXF6PTrmOrnv5R83JEXZpNcO/kAzalTZaDrkoqx1roq2HOjK21J2DG qmtPF5Gzhsg1lYTZQSGSQpOx2c1kYMTNmjxWLppe3r+0GzqkK0FUOYeuPKe2ZHm3Vaqk GkNg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=8eiUt/6y7NKmN4eQ07N4jPkd9JJGEP9k2tD5IVIlXFI=; b=BG+ykNzIwS7pN24M5gS/t2iK5rH2rj1Jm98MF98rUrRG5m+14D49937bIIiwChWheD zjXO3T7axkuGHBQtLrQu9t3WKA2DVM3J0k42heeIzDQM1NAH8fgDai+usPSP9hSu9XkS o1dzJpL0rbVQaprQQbkKuL4SNpFY9ycGV4QAF4UanZrD62GGQ+jN4rdhDyVtlLqc+b0K a7sKQh7BU4kyd/D83GEtCdnsk7c1lfVT8qq9E0Mky3K2Qtp6gnKdDkaV9HL6QHh9s5C7 aGv/x6ynDpHD+Ckz8r9R+xG7qKU4E4zNnYRGFYVFCDs4u5CMFZfS40jdn8SaFtK3tB87 FXBQ== X-Gm-Message-State: AOPr4FXAfi1AAbBb85jGZKuc+ZC9aCQFcOhnJtSxySdRJHUsfrQsFUELzcb4qUiVGCRwfN58RTkF3v2QVnUdMQ== X-Received: by 10.25.17.67 with SMTP id g64mr9315842lfi.112.1460719998958; Fri, 15 Apr 2016 04:33:18 -0700 (PDT) Received: by 10.112.167.10 with HTTP; Fri, 15 Apr 2016 04:32:49 -0700 (PDT) In-Reply-To: Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Archived-At: On Fri, Apr 15, 2016 at 6:18 PM, Christian Couder wrote: > On Fri, Apr 15, 2016 at 11:51 AM, Duy Nguyen wrote: >> On Fri, Apr 15, 2016 at 12:04:49AM +0200, Christian Couder wrote: >>> >>> There is a draft of an article about the first part of the Contributor >>> Summit in the draft of the next Git Rev News edition: >>> >>> https://github.com/git/git.github.io/blob/master/rev_news/drafts/edition-14.md >> >> Thanks. I read the sentence "This made people mention potential >> problems with parallelizing git checkout" and wondered what these >> problems were. > > It may have been Michael or Peff (CC'ed) saying that it could break > some builds as the timestamps on the files might not always be ordered > in the same way. Very subtle. I suppose if we dumb down the distribution algorithm, we could make it stable (even though it won't be the same as serial checkout). Performance will degrade, not sure if it's still worth parallelizing at that point > Now perhaps parallel checkout could be activated only if a config > option was set. (Yeah, I know it looks like I am very often asking for > config options.) And I think it could be unconditionally activated at clone time (I can't imagine different timestamp order can affect anything at that point), where the number of files to checkout is biggest. -- Duy