On 1/6/2021 8:37 PM, Junio C Hamano wrote:

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

quoted

diff --git a/revision.c b/revision.c
index 9dff845bed6..1bb590ece78 100644
--- a/revision.c
+++ b/revision.c

@@ -3308,6 +3308,26 @@ struct topo_walk_info {
 	struct author_date_slab author_date;
 };
 
+static int topo_walk_atexit_registered;
+static unsigned int count_explore_walked;
+static unsigned int count_indegree_walked;
+static unsigned int count_topo_walked;

The revision walk machinery is designed to be callable more than
once during the lifetime of a process.  These make readers wonder
if they should be defined in "struct rev_info" to allow stats
collected per traversal.

That's possible, but the use of an at-exit method means we only
report one set of statistics and the 'struct rev_info' might
be defunct.

It does limit how useful the statistics can be when there are
multiple 'struct rev_info's in use, but we also cannot trust
that the rev_infos are being cleaned up properly at the end
of the process to trigger the stats logging.

Of course, maybe that _is_ something we could guarantee, or
rather _should_ guarantee by patching any leaks. Seems like
a lot of work when these aggregate statistics will be
effective enough. But maybe I'm judging the potential work
too harshly?

Thanks,
-Stolee