Re: [PATCH v4 0/7] Use generation numbers for --topo-order

"Derrick Stolee via GitGitGadget" [off-list ref] writes:

This patch series performs a decently-sized refactoring of the revision-walk
machinery. Well, "refactoring" is probably the wrong word, as I don't
actually remove the old code. Instead, when we see certain options in the
'rev_info' struct, we redirect the commit-walk logic to a new set of methods
that distribute the workload differently. By using generation numbers in the
commit-graph, we can significantly improve 'git log --graph' commands (and
the underlying 'git rev-list --topo-order').

On the Linux repository, I got the following performance results when
comparing to the previous version with or without a commit-graph:

Test: git rev-list --topo-order -100 HEAD
HEAD~1, no commit-graph: 6.80 s
HEAD~1, w/ commit-graph: 0.77 s
  HEAD, w/ commit-graph: 0.02 s

Test: git rev-list --topo-order -100 HEAD -- tools
HEAD~1, no commit-graph: 9.63 s
HEAD~1, w/ commit-graph: 6.06 s
  HEAD, w/ commit-graph: 0.06 s

I wonder if we could make use of existing infrstructure in 't/perf/' to
perform those benchmarks for us (perhaps augmented with large
repository, and only if requested -- similarly to how long tests are
handled).

--
Jakub Narębski