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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 2E349C433E0 for ; Thu, 30 Jul 2020 07:49:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 066252074B for ; Thu, 30 Jul 2020 07:49:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="QisGtSUk" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728877AbgG3HtH (ORCPT ); Thu, 30 Jul 2020 03:49:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49888 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725892AbgG3HtG (ORCPT ); Thu, 30 Jul 2020 03:49:06 -0400 Received: from mail-pg1-x542.google.com (mail-pg1-x542.google.com [IPv6:2607:f8b0:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 82EB8C061794 for ; Thu, 30 Jul 2020 00:49:06 -0700 (PDT) Received: by mail-pg1-x542.google.com with SMTP id w2so16060359pgg.10 for ; Thu, 30 Jul 2020 00:49:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:reply-to:references:mime-version :content-disposition:in-reply-to; bh=vQr1U895+R8OSaltxewuoU8Zm2XTHVlN9lB1vg6bqng=; b=QisGtSUkaCRzJWpVqHdXLJp746kowCkCJtQ0jRrSPeHPDr1k4TiXrnNYD85xUm6W4A 8/eUsfC+FCAqfbnc2YvjFyCO2NC/j7QBT7viDyERS0710Ki3e339UHHEiivfG+ipr6o7 zIOGBSi4//u4YeMBZXsYrGK5RgQq9cubxOX08r3FCYMulDb7RBw5bmLEtMim4Fano6DD KGJDkX+XXU/9wUsCv0ATQzC5pKCFocsQlqmKpYoqHw7IldABR3NURd4kP9jhd8qEAgHF SyvUZ7cYjYCPcqvI0oNN7iJG9RZ2ZvS1aKbBnD+B9gPiN4AFn6o8ctteoIPhbaVcpH3d 5YUg== 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:reply-to :references:mime-version:content-disposition:in-reply-to; bh=vQr1U895+R8OSaltxewuoU8Zm2XTHVlN9lB1vg6bqng=; b=VmrNZaEI+fzax0tHSti7vmwZ2QNS3qlyM4RlSPKy3i5XzPuf2+eE5TXJlSRV9V3yWi 1NOhMxO65vf+Ur5kLLynJs+hMfj8XYibw/q2jgxn907hlwTGghzaWjt6+CBQMjf4XFqL 98mpEzc6fpjn9ZJngcP/6Wsh+2WbrwzI+juQD7usq1mrg0IIPwjuRKK14IPm5s5uDzfj /h4RnsePIoEmNRoKb117VIVjXsQY6gz2E+CRPWv4y6NejJ0SLU+XWT5CP78bjo8Hv7Xj 9uLh/9CZwsf+2GKXpNg/nsoQSWS09KYVLIUZX6Iz/6BK2diO2Na6Q+DyErACUgwgJ3lM qSOA== X-Gm-Message-State: AOAM5307Z2uoU7BsJ+Bg5ycWnJJLN3xsgAgvM+st2D70cXXVlwCwvryI n2bEBPq8AWvvy8j7YnlV8BupGtzek0K9qQ== X-Google-Smtp-Source: ABdhPJypnkSjR4rk8+l1Mc8BOFENTMkahwRRp15NXBBnBNg6yfY5DNFBhao6j7LSH+QQsNa3UfdWFQ== X-Received: by 2002:a63:d501:: with SMTP id c1mr33207846pgg.159.1596095345992; Thu, 30 Jul 2020 00:49:05 -0700 (PDT) Received: from Abhishek-Arch ([2409:4064:208c:7cf0:d18:2f72:fb83:4831]) by smtp.gmail.com with ESMTPSA id h1sm5141581pgn.41.2020.07.30.00.49.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2020 00:49:04 -0700 (PDT) Date: Thu, 30 Jul 2020 13:17:01 +0530 From: Abhishek Kumar To: Taylor Blau Cc: git@vger.kernel.org, gitgitgadget@gmail.com, abhishekkumar8222@gmail.com Subject: Re: [PATCH 0/6] [GSoC] Implement Corrected Commit Date Message-ID: <20200730074701.GA10743@Abhishek-Arch> Reply-To: 20200728145458.GA87373@syl.lan References: <20200728145458.GA87373@syl.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200728145458.GA87373@syl.lan> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Tue, Jul 28, 2020 at 10:54:58AM -0400, Taylor Blau wrote: > Hi Abhishek, > > On Tue, Jul 28, 2020 at 09:13:45AM +0000, Abhishek Kumar via GitGitGadget wrote: > > This patch series implements the corrected commit date offsets as generation > > number v2, along with other pre-requisites. > > Very exciting. I have been eagerly following your blog and asking > Stolee about your progress, so I am excited to read these patches. > I am so glad to hear that! > > [...] > > I'm sure that I'll learn more when I get to this point, but I would like > to hear more about why you want to store the offset rather than the > corrected commit date itself. It seems that the offset could be either > positive or negative, so you'd only have the range of a signed integer > (rather than storing 8 bytes of a time_t for the full breadth of > possibilities). > Corrected commit dates are at least as big as the committer date, so the offset (i.e. corrected date - committer date) would never be negative. We store offsets instead of corrected commit dates because: - We save 4 bytes for each commit, which amounts to 7-8% of the size of commit graph file (of course, dependent on the other chunks used). - We save some time while writing the commit-graph file too, around ~200ms for the Linux repo. While the savings are modest, writing corrected dates does not offer any advantage that we could think of, at the time. > I know also that Peff is working on negative timestamp support, so I > would want to hear about what he thinks of this, too. I have read up on Peff's work with negative timestamp support and it's pretty exciting. > [...] Thanks - Abhishek