[PATCH v6 10/10] kunit: string-stream: Test performance of string_stream

Richard Fitzgerald
2023-08-28T10:42:46Z

Add a test of the speed and memory use of string_stream.

string_stream_performance_test() doesn't actually "test" anything (it
cannot fail unless the system has run out of allocatable memory) but it
measures the speed and memory consumption of the string_stream and reports
the result.

This allows changes in the string_stream implementation to be compared.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: David Gow <davidgow@google.com>
---
lib/kunit/string-stream-test.c | 54 ++++++++++++++++++++++++++++++++++
1 file changed, 54 insertions(+)

diff --git a/lib/kunit/string-stream-test.c b/lib/kunit/string-stream-test.c
index b759974d9cec..06822766f29a 100644
--- a/lib/kunit/string-stream-test.c
+++ b/lib/kunit/string-stream-test.c
@@ -8,7 +8,9 @@

#include <kunit/static_stub.h>
#include <kunit/test.h>
+#include <linux/ktime.h>
#include <linux/slab.h>
+#include <linux/timekeeping.h>

#include "string-stream.h"

@@ -454,6 +456,57 @@ static void string_stream_auto_newline_test(struct kunit *test)
"One\nTwo\nThree\nFour\nFive\nSix\nSeven\n\nEight\n");
}

+/*
+ * This doesn't actually "test" anything. It reports time taken
+ * and memory used for logging a large number of lines.
+ */
+static void string_stream_performance_test(struct kunit *test)
+{
+ struct string_stream_fragment *frag_container;
+ struct string_stream *stream;
+ char test_line[101];
+ ktime_t start_time, end_time;
+ size_t len, bytes_requested, actual_bytes_used, total_string_length;
+ int offset, i;
+
+ stream = kunit_alloc_string_stream(test, GFP_KERNEL);
+ KUNIT_ASSERT_NOT_ERR_OR_NULL(test, stream);
+
+ memset(test_line, 'x', sizeof(test_line) - 1);
+ test_line[sizeof(test_line) - 1] = '\0';
+
+ start_time = ktime_get();
+ for (i = 0; i < 10000; i++) {
+ offset = i % (sizeof(test_line) - 1);
+ string_stream_add(stream, "%s: %d\n", &test_line[offset], i);
+ }
+ end_time = ktime_get();
+
+ /*
+ * Calculate memory used. This doesn't include invisible
+ * overhead due to kernel allocator fragment size rounding.
+ */
+ bytes_requested = sizeof(*stream);
+ actual_bytes_used = ksize(stream);
+ total_string_length = 0;
+
+ list_for_each_entry(frag_container, &stream->fragments, node) {
+ bytes_requested += sizeof(*frag_container);
+ actual_bytes_used += ksize(frag_container);
+
+ len = strlen(frag_container->fragment);
+ total_string_length += len;
+ bytes_requested += len + 1; /* +1 for '\0' */
+ actual_bytes_used += ksize(frag_container->fragment);
+ }
+
+ kunit_info(test, "Time elapsed: %lld us\n",
+ ktime_us_delta(end_time, start_time));
+ kunit_info(test, "Total string length: %zu\n", total_string_length);
+ kunit_info(test, "Bytes requested: %zu\n", bytes_requested);
+ kunit_info(test, "Actual bytes allocated: %zu\n", actual_bytes_used);
+}
+
static int string_stream_test_init(struct kunit *test)
{
struct string_stream_test_priv *priv;
@@ -479,6 +532,7 @@ static struct kunit_case string_stream_test_cases[] = {
KUNIT_CASE(string_stream_append_empty_string_test),
KUNIT_CASE(string_stream_no_auto_newline_test),
KUNIT_CASE(string_stream_auto_newline_test),
+ KUNIT_CASE(string_stream_performance_test),
{}
};

--
2.30.2