user/dev discussion of public-inbox itself
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From: Eric Wong <>
Subject: [PATCH 4/4] v2writable: short-circuit is_ancestor check on equality
Date: Thu, 30 May 2019 06:52:27 +0000
Message-ID: <> (raw)
In-Reply-To: <>

We don't need to use git to check ancestry if object IDs
match on a string comparison.

This saves 100ms or so and brings down the ~0.5s no-op time on down to ~0.4s.
 lib/PublicInbox/ | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/PublicInbox/ b/lib/PublicInbox/
index fd93ac2..76844cd 100644
--- a/lib/PublicInbox/
+++ b/lib/PublicInbox/
@@ -831,6 +831,12 @@ sub log_range ($$$$$) {
 		return $tip; # all of it
+	# fast equality check to avoid (v)fork+execve overhead
+	if ($cur eq $tip) {
+		$sync->{ranges}->[$i] = undef;
+		return;
+	}
 	my $range = "$cur..$tip";
 	$pr->("$i.git checking contiguity... ") if $pr;
 	if (is_ancestor($git, $cur, $tip)) { # common case

      parent reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-30  6:52 [PATCH 0/4] v2writable: speedup no-op -index invocation Eric Wong
2019-05-30  6:52 ` [PATCH 1/4] v2writable: split off unindex_range mapping Eric Wong
2019-05-30  6:52 ` [PATCH 2/4] v2writable: hoist out index_epoch sub Eric Wong
2019-05-30  6:52 ` [PATCH 3/4] v2writable: avoid mm_tmp creation without regen Eric Wong
2019-05-30  6:52 ` Eric Wong [this message]

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