On Wed, Jun 25, 2025, at 13:28, Andrzej Dębski wrote: > One of Dropbox SWEs observed that a specific git command in Go > language tooling > https://github.com/golang/go/blob/e515ef8bc271f632bb2ebb94e8e700ab67274268/src/cmd/go/internal/modfetch/codehost/git.go#L758 > took over 20 seconds. Internally we distribute git 2.46.0 right now > but the SWE had an older version of git around (2.39.5) and observed a > performance regression between those 2 versions. > > We've did some performance measurements and the command like "git > for-each-ref --format="%(refname)" refs/tags --merged HEAD > > /dev/null" > spent majority of time in function "tips_reachable_from_bases" > introduced in git 2.40.0: > https://github.com/git/git/commit/cbfe360b140fe92d9c4a763bf630c3b8ba431522 > > Similar performance degradation can be observed in git 2.50 > > Given that the command references tags I've experimented and observed > that the command execution time decreased with the amount of tags I've > removed from the local copy of the repo. > > Context: in Dropbox we operate a large monorepo with around 65K tags > right now and growing every day. > > The question is, given the same command used to be much faster in > older versions of git is this considered a regression and can be fixed > in future releases of git? > > > [System Info] > git version: 2.46.0 > cpu: bazel > built from commit: bazel > sizeof-long: 8 > sizeof-size_t: 8 > shell-path: /bin/sh > libcurl: 7.82.0 > OpenSSL: OpenSSL 1.1.1w 11 Sep 2023 > zlib: 1.2.13 > uname: Linux 6.8.0-1029-aws #31~22.04.1-Ubuntu SMP Thu Apr 24 21:16:18 > UTC 2025 x86_64 > compiler info: gnuc: 11.2 > libc info: glibc: 2.35 > $SHELL (typically, interactive shell): /bin/bash +CC author. -- Kristoffer Haugsbakk
