Re: [PATCH 1/6] fetch-pack: clear marks before everything_local()
flat view
From: Jonathan Nieder <hidden>
Date: 2018-06-05 23:08:27
Hi, Jonathan Tan wrote:
If tag following is required when using a transport that does not support tag following, fetch_pack() will be invoked twice in the same process, necessitating a clearing of the object flags used by fetch_pack() sometime during the second invocation. This is currently done in find_common(), which means that the work done by everything_local() in marking complete remote refs as COMMON_REF is wasted. To avoid this wastage, move this clearing from find_common() to its parent function do_fetch_pack(), right before it calls everything_local().
I had to read this a few times and didn't end up understanding it. Is the idea that this will speed something up? Can you provide e.g. "perf stat" output (or even a new perf test in t/perf) demonstrating the improvement? Or is it a cleanup? [...]
quoted hunk ↗ jump to hunk
--- a/fetch-pack.c +++ b/fetch-pack.c@@ -336,9 +336,6 @@ static int find_common(struct fetch_pack_args *args, if (args->stateless_rpc && multi_ack == 1) die(_("--stateless-rpc requires multi_ack_detailed")); - if (marked) - for_each_ref(clear_marks, NULL); - marked = 1; for_each_ref(rev_list_insert_ref_oid, NULL); for_each_cached_alternate(insert_one_alternate_object);@@ -1053,6 +1050,9 @@ static struct ref *do_fetch_pack(struct fetch_pack_args *args, if (!server_supports("deepen-relative") && args->deepen_relative) die(_("Server does not support --deepen")); + if (marked) + for_each_ref(clear_marks, NULL); + marked = 1; if (everything_local(args, &ref, sought, nr_sought)) {
As an experiment, I tried applying the '-' part of the change without the '+' part to get confidence that tests cover this well. To my chagrin, all tests still passed. :/ In the preimage, we call clear_marks in find_common. This is right before we start setting up the revision walk, e.g. by inserting revisions for each ref. In the postimage, we call clear_marks in do_fetch_pack. This is right before we call everything_local. I end up feeling that I don't understand the code well, neither before nor after the patch. Ideas for making it clearer? Thanks, Jonathan