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[83.21.79.40]) by smtp.gmail.com with ESMTPSA id y18sm21772915wmd.29.2019.05.20.04.02.37 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 20 May 2019 04:02:38 -0700 (PDT) From: Jakub Narebski To: Derrick Stolee Cc: Mike Hommey , SZEDER =?utf-8?Q?G=C3=A1bor?= , git@vger.kernel.org Subject: Re: Revision walking, commit dates, slop References: <20190518005412.n45pj5p2rrtm2bfj@glandium.org> <20190518015005.GA951@szeder.dev> <20190518035828.pjaqfrkkvldhri6v@glandium.org> <20190518041706.ct6ie5trvxgdhjar@glandium.org> Date: Mon, 20 May 2019 13:02:36 +0200 In-Reply-To: (Derrick Stolee's message of "Sun, 19 May 2019 21:33:08 -0400") Message-ID: <86mujhpewj.fsf@gmail.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (windows-nt) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Derrick Stolee writes: > On 5/18/2019 12:17 AM, Mike Hommey wrote: >> On Sat, May 18, 2019 at 12:58:28PM +0900, Mike Hommey wrote: >>> On Sat, May 18, 2019 at 03:50:05AM +0200, SZEDER G=C3=A1bor wrote: >>>> >>>> All the above is without commit-graph, I presume? If so, then you >>>> should give it a try, as it might bring immediate help in your >>>> pathological repo. With 5k commit in the same second (enforced via >>>> 'export GIT_COMMITTER_DATE=3D$(date); for i in {1..5000} ...') I get: >>>> >>>> $ best-of-five -q git rev-list HEAD~..HEAD >>>> 0.069 >>>> $ git commit-graph write --reachableComputing commit graph generation >>>> numbers: 100% (5000/5000), done. >>>> $ best-of-five -q git rev-list HEAD~..HEAD >>>> 0.004 >>> >>> I'm not observing any difference from using commit-graph, whether in >>> time or in the number of commits that are looked at in limit_list(). >>=20 >> -c core.commitGraph=3Dtrue does make a difference in time, but not in the >> number of commits looked at in limit_list(). So it's only faster because >> each iteration of the loop is faster. It means it's still dependent on >> the depth of the dag, and the larger the repo will grow, the slower it >> will get. > > The plan is to use the commit-graph's generation numbers for these A..B > queries, but due to some cases when commit date is a _better_ heuristic > than generation numbers, we have not enabled them for A..B. You'll see > that 'git rev-list --topo-order -n 1 HEAD` will be much faster with the > commit-graph, but adding '--topo-order' to your 'HEAD~1..HEAD' query > should not change the time at all. > > See [1] for the discussion about "generation number v2" which will allow > us to use a better heuristic in these cases. > > [1] https://public-inbox.org/git/6367e30a-1b3a-4fe9-611b-d931f51effef@gma= il.com/ Are there any blockers that prevent the switch to this "generation number v2"? - Is it a problem with insufficient data to choose the correct numbering as "generation number v2' (there can be only one)? - Is it a problem with selected "generation number v2" being incompatibile with gen v2, and Git failing when new version of commit-graph is used instead of softly just not using commit-graph? - Or is it something else? Best, -- Jakub Nar=C4=99bski