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SubjectRe: [PATCH v2 5/6] userfaultfd: selftests: make /dev/userfaultfd testing configurable
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On 4/22/22 3:29 PM, Axel Rasmussen wrote:
> Instead of always testing both userfaultfd(2) and /dev/userfaultfd,
> let the user choose which to test.
>
> As with other test features, change the behavior based on a new
> command line flag. Introduce the idea of "test mods", which are
> generic (not specific to a test type) modifications to the behavior of
> the test. This is sort of borrowed from this RFC patch series [1], but
> simplified a bit.
>
> The benefit is, in "typical" configurations this test is somewhat slow
> (say, 30sec or something). Testing both clearly doubles it, so it may
> not always be desirable, as users are likely to use one or the other,
> but never both, in the "real world".
>
> [1]: https://patchwork.kernel.org/project/linux-mm/patch/20201129004548.1619714-14-namit@vmware.com/
>
> Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
> ---
> tools/testing/selftests/vm/userfaultfd.c | 41 +++++++++++++++++-------
> 1 file changed, 30 insertions(+), 11 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 12ae742a9981..274522704e40 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -142,8 +142,17 @@ static void usage(void)
> {
> fprintf(stderr, "\nUsage: ./userfaultfd <test type> <MiB> <bounces> "
> "[hugetlbfs_file]\n\n");
> +

Remove the extra blank line here.

> fprintf(stderr, "Supported <test type>: anon, hugetlb, "
> "hugetlb_shared, shmem\n\n");
> +

Remove the extra blank line here.

> + fprintf(stderr, "'Test mods' can be joined to the test type string with a ':'. "
> + "Supported mods:\n");
> + fprintf(stderr, "\tdev - Use /dev/userfaultfd instead of userfaultfd(2)\n");
> + fprintf(stderr, "\nExample test mod usage:\n");
> + fprintf(stderr, "# Run anonymous memory test with /dev/userfaultfd:\n");
> + fprintf(stderr, "./userfaultfd anon:dev 100 99999\n\n");
> +
> fprintf(stderr, "Examples:\n\n");
> fprintf(stderr, "%s", examples);

Update examples above with new test cases if any.

> exit(1);
> @@ -1610,8 +1619,6 @@ unsigned long default_huge_page_size(void)
>
> static void set_test_type(const char *type)
> {
> - uint64_t features = UFFD_API_FEATURES;
> -
> if (!strcmp(type, "anon")) {
> test_type = TEST_ANON;
> uffd_test_ops = &anon_uffd_test_ops;
> @@ -1631,10 +1638,28 @@ static void set_test_type(const char *type)
> test_type = TEST_SHMEM;
> uffd_test_ops = &shmem_uffd_test_ops;
> test_uffdio_minor = true;
> - } else {
> - err("Unknown test type: %s", type);
> + }

At this point, it might make it so much easier and maintainable if
we were to use getopt instead of parsing options.

> +}
> +
> +static void parse_test_type_arg(const char *raw_type)
> +{
> + char *buf = strdup(raw_type);
> + uint64_t features = UFFD_API_FEATURES;
> +
> + while (buf) {
> + const char *token = strsep(&buf, ":");
> +
> + if (!test_type)
> + set_test_type(token);
> + else if (!strcmp(token, "dev"))
> + test_dev_userfaultfd = true;
> + else
> + err("unrecognized test mod '%s'", token);
> }
>
> + if (!test_type)
> + err("failed to parse test type argument: '%s'", raw_type);
> +
> if (test_type == TEST_HUGETLB)
> page_size = default_huge_page_size();
> else
> @@ -1681,7 +1706,7 @@ int main(int argc, char **argv)
> err("failed to arm SIGALRM");
> alarm(ALARM_INTERVAL_SECS);
>
> - set_test_type(argv[1]);
> + parse_test_type_arg(argv[1]);
>
> nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> nr_pages_per_cpu = atol(argv[2]) * 1024*1024 / page_size /
> @@ -1719,12 +1744,6 @@ int main(int argc, char **argv)
> }
> printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
> nr_pages, nr_pages_per_cpu);
> -
> - test_dev_userfaultfd = false;
> - if (userfaultfd_stress())
> - return 1;
> -
> - test_dev_userfaultfd = true;
> return userfaultfd_stress();
> }
>
>

Same comments as before on fail vs. skip conditions to watch out
for and report them correctly.

thanks,
-- Shuah

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