Merge branch 'jh/string-list-micro-optim'

The string-list API used a custom reallocation strategy that was
very inefficient, instead of using the usual ALLOC_GROW() macro,
which has been fixed.

* jh/string-list-micro-optim:
  string-list: use ALLOC_GROW macro when reallocing string_list

2 files changed, 50 insertions, 4 deletions

diff --git a/string-list.c b/string-list.c
index 45016ad86d..003ca1879e 100644
--- a/string-list.c
+++ b/string-list.c
@@ -41,10 +41,7 @@ static int add_entry(int insert_at, struct string_list *list, const char *string
 	if (exact_match)
 		return -1 - index;
 
-	if (list->nr + 1 >= list->alloc) {
-		list->alloc += 32;
-		REALLOC_ARRAY(list->items, list->alloc);
-	}
+	ALLOC_GROW(list->items, list->nr+1, list->alloc);
 	if (index < list->nr)
 		memmove(list->items + index + 1, list->items + index,
 				(list->nr - index)
diff --git a/t/perf/p0005-status.sh b/t/perf/p0005-status.sh
new file mode 100755
index 0000000000..0b0aa9858f
--- /dev/null
+++ b/t/perf/p0005-status.sh
@@ -0,0 +1,49 @@
+#!/bin/sh
+#
+# This test measures the performance of various read-tree
+# and status operations.  It is primarily interested in
+# the algorithmic costs of index operations and recursive
+# tree traversal -- and NOT disk I/O on thousands of files.
+
+test_description="Tests performance of read-tree"
+
+. ./perf-lib.sh
+
+test_perf_default_repo
+
+# If the test repo was generated by ./repos/many-files.sh
+# then we know something about the data shape and branches,
+# so we can isolate testing to the ballast-related commits
+# and setup sparse-checkout so we don't have to populate
+# the ballast files and directories.
+#
+# Otherwise, we make some general assumptions about the
+# repo and consider the entire history of the current
+# branch to be the ballast.
+
+test_expect_success "setup repo" '
+	if git rev-parse --verify refs/heads/p0006-ballast^{commit}
+	then
+		echo Assuming synthetic repo from many-files.sh
+		git branch br_base            master
+		git branch br_ballast         p0006-ballast
+		git config --local core.sparsecheckout 1
+		cat >.git/info/sparse-checkout <<-EOF
+		/*
+		!ballast/*
+		EOF
+	else
+		echo Assuming non-synthetic repo...
+		git branch br_base            $(git rev-list HEAD | tail -n 1)
+		git branch br_ballast         HEAD
+	fi &&
+	git checkout -q br_ballast &&
+	nr_files=$(git ls-files | wc -l)
+'
+
+test_perf "read-tree status br_ballast ($nr_files)" '
+	git read-tree HEAD &&
+	git status
+'
+
+test_done