mark_parents_uninteresting(): avoid most allocation
Commit 941ba8db57 (Eliminate recursion in setting/clearing marks in commit list, 2012-01-14) used a clever double-loop to avoid allocations for single-parent chains of history. However, it did so only when following parents of parents (which was an uncommon case), and _always_ incurred at least one allocation to populate the list of pending parents in the first place. We can turn this into zero-allocation in the common case by iterating directly over the initial parent list, and then following up on any pending items we might have discovered. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Jeff King committed
May 11, 2018 at 14:03 UTC
8702b30fd7b6c804f1bb59877a4c2f773fbe00f8
1 file changed
+25
-19
revision.c
+25
-19
@@ -114,32 +114,38 @@ static void commit_stack_clear(struct commit_stack *stack)
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stack->nr = stack->alloc = 0;
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}
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-void mark_parents_uninteresting(struct commit *commit)
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+static void mark_one_parent_uninteresting(struct commit *commit,
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+ struct commit_stack *pending)
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{
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- struct commit_stack pending = COMMIT_STACK_INIT;
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struct commit_list *l;
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+ if (commit->object.flags & UNINTERESTING)
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+ return;
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+ commit->object.flags |= UNINTERESTING;
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+
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+ /*
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+ * Normally we haven't parsed the parent
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+ * yet, so we won't have a parent of a parent
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+ * here. However, it may turn out that we've
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+ * reached this commit some other way (where it
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+ * wasn't uninteresting), in which case we need
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+ * to mark its parents recursively too..
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+ */
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for (l = commit->parents; l; l = l->next)
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- commit_stack_push(&pending, l->item);
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+ commit_stack_push(pending, l->item);
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+}
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- while (pending.nr > 0) {
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- struct commit *commit = commit_stack_pop(&pending);
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+void mark_parents_uninteresting(struct commit *commit)
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+{
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+ struct commit_stack pending = COMMIT_STACK_INIT;
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+ struct commit_list *l;
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- if (commit->object.flags & UNINTERESTING)
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- return;
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- commit->object.flags |= UNINTERESTING;
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+ for (l = commit->parents; l; l = l->next)
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+ mark_one_parent_uninteresting(l->item, &pending);
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- /*
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- * Normally we haven't parsed the parent
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- * yet, so we won't have a parent of a parent
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- * here. However, it may turn out that we've
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- * reached this commit some other way (where it
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- * wasn't uninteresting), in which case we need
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- * to mark its parents recursively too..
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- */
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- for (l = commit->parents; l; l = l->next)
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- commit_stack_push(&pending, l->item);
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- }
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+ while (pending.nr > 0)
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+ mark_one_parent_uninteresting(commit_stack_pop(&pending),
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+ &pending);
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commit_stack_clear(&pending);
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}