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([2001:4898:8010:0:ae1c:7a22:56f1:df04]) by smtp.gmail.com with ESMTPSA id q184sm3930063qkf.79.2018.04.04.08.48.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 04 Apr 2018 08:48:43 -0700 (PDT) Subject: Re: [PATCH 8/6] commit: use generation numbers for in_merge_bases() To: Derrick Stolee , git@vger.kernel.org Cc: peff@peff.net, avarab@gmail.com, sbeller@gmail.com, larsxschneider@gmail.com, bmwill@google.com References: <20180403190500.GA10930@sigill.intra.peff.net> <20180404154554.140716-1-dstolee@microsoft.com> <20180404154554.140716-2-dstolee@microsoft.com> From: Derrick Stolee Message-ID: <14e4e1d3-5c77-dc7c-10d5-e9406b992f0e@gmail.com> Date: Wed, 4 Apr 2018 11:48:42 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180404154554.140716-2-dstolee@microsoft.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On 4/4/2018 11:45 AM, Derrick Stolee wrote: > 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. > > 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% > > Reported-by: Jeff King > Signed-off-by: Derrick Stolee > --- > commit.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/commit.c b/commit.c > index 858f4fdbc9..2566cba79f 100644 > --- a/commit.c > +++ b/commit.c > @@ -1059,12 +1059,19 @@ 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_UNDEF; > > 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; > > bases = paint_down_to_common(commit, nr_reference, reference); > if (commit->object.flags & PARENT2) This patch may suffice to speed up 'git branch --contains' instead of needing to always use the 'git tag --contains' algorithm as considered in [1]. Thanks, -Stolee [1] https://public-inbox.org/git/20180303051516.GE27689@sigill.intra.peff.net/     Re: [PATCH 0/4] Speed up git tag --contains