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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 29802C433EF for ; Thu, 24 Feb 2022 22:55:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229674AbiBXW4B (ORCPT ); Thu, 24 Feb 2022 17:56:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229501AbiBXWz7 (ORCPT ); Thu, 24 Feb 2022 17:55:59 -0500 Received: from pb-smtp21.pobox.com (pb-smtp21.pobox.com [173.228.157.53]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2DCDB20A94A for ; Thu, 24 Feb 2022 14:55:27 -0800 (PST) Received: from pb-smtp21.pobox.com (unknown [127.0.0.1]) by pb-smtp21.pobox.com (Postfix) with ESMTP id 9C28918416C; Thu, 24 Feb 2022 17:55:26 -0500 (EST) (envelope-from junio@pobox.com) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=pobox.com; h=from:to:cc :subject:references:date:in-reply-to:message-id:mime-version :content-type; s=sasl; bh=OahmJ4tMGmzocVtSJzem/MQp27EowP3pE3a26/ /iL98=; b=l63z23VNdnR8YY3ZrnuXXzQkZeRIvBdp7jG64iqKCgpFyxZkM9UckR erhD+nb8BhP4kJIRvZTPLwrgj6ytdR9eoTw3AraGUYfHQfaLm4cRp2a00RxA/bLU xMKHkMdgZPOdgJeaqbwzWz5njL35d8ibZh07kgyU/mfPXzgAQ92yI= Received: from pb-smtp21.sea.icgroup.com (unknown [127.0.0.1]) by pb-smtp21.pobox.com (Postfix) with ESMTP id 9288518416A; Thu, 24 Feb 2022 17:55:26 -0500 (EST) (envelope-from junio@pobox.com) Received: from pobox.com (unknown [34.82.80.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by pb-smtp21.pobox.com (Postfix) with ESMTPSA id 08640184169; Thu, 24 Feb 2022 17:55:24 -0500 (EST) (envelope-from junio@pobox.com) From: Junio C Hamano To: "Derrick Stolee via GitGitGadget" Cc: git@vger.kernel.org, me@ttaylorr.com, abhishekkumar8222@gmail.com, Derrick Stolee Subject: Re: [PATCH 5/7] commit-graph: document file format v2 References: <7f9b65bd22551fd7fd5d2f0bf18aee8c25f1db99.1645735117.git.gitgitgadget@gmail.com> Date: Thu, 24 Feb 2022 14:55:23 -0800 In-Reply-To: <7f9b65bd22551fd7fd5d2f0bf18aee8c25f1db99.1645735117.git.gitgitgadget@gmail.com> (Derrick Stolee via GitGitGadget's message of "Thu, 24 Feb 2022 20:38:34 +0000") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Pobox-Relay-ID: D9B873F2-95C4-11EC-8FCE-CBA7845BAAA9-77302942!pb-smtp21.pobox.com Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org "Derrick Stolee via GitGitGadget" writes: > From: Derrick Stolee > > The corrected commit date was first documented in 5a3b130ca (doc: add > corrected commit date info, 2021-01-16) and it used an optional chunk to > augment the commit-graph format without modifying the file format > version. > > One major benefit to this approach is that corrected commit dates could > be written without causing a backwards compatibility issue with Git > versions that do not understand them. The topological level was still > available in the CDAT chunk as it was before. > > However, this causes a different issue: more data needs to be loaded > from disk when parsing commits from the commit-graph. In cases where > there is no significant algorithmic gain from using corrected commit > dates, commit walks take up to 20% longer because of this extra data. > > Create a new file format version for the commit-graph format that > differs only in the CDAT chunk: it now stores corrected commit date > offsets. This brings our data back to normal and will demonstrate > performance gains in almost all cases. OK.