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Date:   Tue, 14 Jun 2022 15:43:04 -0400
From:   Peter Xu <peterx@redhat.com>
To:     Axel Rasmussen <axelrasmussen@google.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Charan Teja Reddy <charante@codeaurora.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "Dmitry V . Levin" <ldv@altlinux.org>,
        Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>,
        Hugh Dickins <hughd@google.com>, Jan Kara <jack@suse.cz>,
        Jonathan Corbet <corbet@lwn.net>,
        Mel Gorman <mgorman@techsingularity.net>,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Mike Rapoport <rppt@kernel.org>, Nadav Amit <namit@vmware.com>,
        Shuah Khan <shuah@kernel.org>,
        Suren Baghdasaryan <surenb@google.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        zhangyi <yi.zhang@huawei.com>, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v3 5/6] userfaultfd: selftests: make /dev/userfaultfd
 testing configurable
Message-ID: <YqjkyFIgPSuXK+dz@xz-m1.local>
References: <20220601210951.3916598-1-axelrasmussen@google.com>
 <20220601210951.3916598-6-axelrasmussen@google.com>
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On Wed, Jun 01, 2022 at 02:09:50PM -0700, 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".

Yes, when I was reading your other patch I was wishing no timeout of any of
QE testbeds could trigger.

If you plan to remove it anyway, mind to squash these?

> 
> [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 1badb5d31bf9..aeee6f1ad8ef 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -128,6 +128,8 @@ struct uffd_stats {
>  const char *examples =
>      "# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
>      "./userfaultfd anon 100 99999\n\n"
> +    "# Run the same anonymous memory test, but using /dev/userfaultfd:\n"
> +    "./userfaultfd anon:dev 100 99999\n\n"
>      "# Run share memory test on 1GiB region with 99 bounces:\n"
>      "./userfaultfd shmem 1000 99\n\n"
>      "# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
> @@ -144,6 +146,13 @@ static void usage(void)
>  		"[hugetlbfs_file]\n\n");
>  	fprintf(stderr, "Supported <test type>: anon, hugetlb, "
>  		"hugetlb_shared, shmem\n\n");
> +	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");

That looks better than running everything by default twice. Though let's
also provide "syscall" if we're at it, anyway?

Thanks,

> +	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);
>  	exit(1);
> @@ -1607,8 +1616,6 @@ 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;
> @@ -1626,10 +1633,28 @@ 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);
> +	}
> +}
> +
> +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
> @@ -1676,7 +1701,7 @@ 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 /
> @@ -1714,12 +1739,6 @@ 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();
>  }
>  
> -- 
> 2.36.1.255.ge46751e96f-goog
> 

-- 
Peter Xu