linux-kernel - Re: [PATCH v4 10/10] kunit: string-stream: Test performance of string

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Message-ID: <CABVgOSnXHg9Vf=818P3usDquF0JWx2oem48fSV4krL_MTGcVCA@mail.gmail.com>
Date:   Tue, 15 Aug 2023 17:17:08 +0800
From:   David Gow <davidgow@...gle.com>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     brendan.higgins@...ux.dev, rmoar@...gle.com,
        linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com
Subject: Re: [PATCH v4 10/10] kunit: string-stream: Test performance of string_stream

On Mon, 14 Aug 2023 at 21:23, Richard Fitzgerald
<rf@...nsource.cirrus.com> wrote:
>
> 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@...nsource.cirrus.com>
> ---

Thanks, this is very useful.

My results are (UML):
   # string_stream_performance_test: Time elapsed:           5021 us
   # string_stream_performance_test: Total string length:    573890
   # string_stream_performance_test: Bytes requested:        823930
   # string_stream_performance_test: Actual bytes allocated: 1048312

KUnit isn't really ideal for performance testing, but this works well
enough and fits in well alongside the other string stream tests.

Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David


>  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 05bfade2bd8a..b55cc14f43fb 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"
>
> @@ -370,6 +372,57 @@ 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 = 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;
> @@ -400,6 +453,7 @@ 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
>

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