Merge branch 'kw/write-index-reduce-alloc'

We used to spend more than necessary cycles allocating and freeing
piece of memory while writing each index entry out.  This has been
optimized.

* kw/write-index-reduce-alloc:
  read-cache: avoid allocating every ondisk entry when writing
  read-cache: fix memory leak in do_write_index
  perf: add test for writing the index

2 files changed, 52 insertions, 0 deletions

diff --git a/t/helper/test-write-cache.c b/t/helper/test-write-cache.c
new file mode 100644
index 0000000000..b7ee039669
--- /dev/null
+++ b/t/helper/test-write-cache.c
@@ -0,0 +1,23 @@
+#include "cache.h"
+#include "lockfile.h"
+
+static struct lock_file index_lock;
+
+int cmd_main(int argc, const char **argv)
+{
+	int i, cnt = 1, lockfd;
+	if (argc == 2)
+		cnt = strtol(argv[1], NULL, 0);
+	setup_git_directory();
+	read_cache();
+	for (i = 0; i < cnt; i++) {
+		lockfd = hold_locked_index(&index_lock, LOCK_DIE_ON_ERROR);
+		if (0 <= lockfd) {
+			write_locked_index(&the_index, &index_lock, COMMIT_LOCK);
+		} else {
+			rollback_lock_file(&index_lock);
+		}
+	}
+
+	return 0;
+}
diff --git a/t/perf/p0007-write-cache.sh b/t/perf/p0007-write-cache.sh
new file mode 100755
index 0000000000..261fe92fd9
--- /dev/null
+++ b/t/perf/p0007-write-cache.sh
@@ -0,0 +1,29 @@
+#!/bin/sh
+
+test_description="Tests performance of writing the index"
+
+. ./perf-lib.sh
+
+test_perf_default_repo
+
+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 config --local core.sparsecheckout 1
+		cat >.git/info/sparse-checkout <<-EOF
+		/*
+		!ballast/*
+		EOF
+	else
+		echo Assuming non-synthetic repo...
+	fi &&
+	nr_files=$(git ls-files | wc -l)
+'
+
+count=3
+test_perf "write_locked_index $count times ($nr_files files)" "
+	test-write-cache $count
+"
+
+test_done