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[83.21.66.153]) by smtp.gmail.com with ESMTPSA id e10-v6sm3876267wri.23.2018.04.18.15.15.06 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 18 Apr 2018 15:15:07 -0700 (PDT) From: Jakub Narebski To: Derrick Stolee Cc: git@vger.kernel.org, "peff\@peff.net" , "stolee\@gmail.com" , "avarab\@gmail.com" , "sbeller\@google.com" , "larsxschneider\@gmail.com" , "bmwill\@google.com" , "gitster\@pobox.com" , "sunshine\@sunshineco.com" , "jonathantanmy\@google.com" Subject: Re: [PATCH v3 6/9] commit: use generation numbers for in_merge_bases() References: <20180409164131.37312-1-dstolee@microsoft.com> <20180417170001.138464-1-dstolee@microsoft.com> <20180417170001.138464-7-dstolee@microsoft.com> Date: Thu, 19 Apr 2018 00:15:06 +0200 In-Reply-To: <20180417170001.138464-7-dstolee@microsoft.com> (Derrick Stolee's message of "Tue, 17 Apr 2018 17:00:30 +0000") Message-ID: <86k1t4go0l.fsf@gmail.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (windows-nt) MIME-Version: 1.0 Content-Type: text/plain Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org Derrick Stolee writes: > The containment algorithm for 'git branch --contains' is different > from that for 'git tag --contains' in that it uses is_descendant_of() > instead of contains_tag_algo(). The expensive portion of the branch > algorithm is computing merge bases. > > When a commit-graph file exists with generation numbers computed, > we can avoid this merge-base calculation when the target commit has > a larger generation number than the target commits. You have "target" twice in above paragraph; one of those should probably be something else. > > Performance tests were run on a copy of the Linux repository where > HEAD is contained in v4.13 but no earlier tag. Also, all tags were > copied to branches and 'git branch --contains' was tested: > > Before: 60.0s > After: 0.4s > Rel %: -99.3% Nice... > > Reported-by: Jeff King > Signed-off-by: Derrick Stolee > --- > commit.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) ...especially for so small changes. > > diff --git a/commit.c b/commit.c > index a44899c733..bceb79c419 100644 > --- a/commit.c > +++ b/commit.c > @@ -1053,12 +1053,19 @@ int in_merge_bases_many(struct commit *commit, int nr_reference, struct commit * > { > struct commit_list *bases; > int ret = 0, i; > + uint32_t min_generation = GENERATION_NUMBER_INFINITY; > > if (parse_commit(commit)) > return ret; > - for (i = 0; i < nr_reference; i++) > + for (i = 0; i < nr_reference; i++) { > if (parse_commit(reference[i])) > return ret; > + if (min_generation > reference[i]->generation) > + min_generation = reference[i]->generation; > + } > + > + if (commit->generation > min_generation) > + return 0; Why not use "return ret;" instead of "return 0;", like the rest of the code [cryptically] does, that is: + if (commit->generation > min_generation) + return ret; > > bases = paint_down_to_common(commit, nr_reference, reference); > if (commit->object.flags & PARENT2) Otherwise, it looks good to me.