Re: [PATCH v2 1/6] kselftests: vm: Add mremap tests

[John Hubbard <jhubbard@nvidia.com>]

On 10/2/20 9:20 AM, Kalesh Singh wrote:
> Test mremap on regions of various sizes and alignments and validate
> data after remapping. Also provide total time for remapping
> the region which is useful for performance comparison of the mremap
> optimizations that move pages at the PMD/PUD levels if HAVE_MOVE_PMD
> and/or HAVE_MOVE_PUD are enabled.
> 
> Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
> ---
> Changes in v2:
>    - Reduce test time by only validating a certain threshold of the
>      remapped region (4MB by default). The -t flag can be used to
>      set a custom threshold in MB or no threshold by passing 0. (-t0).
>      mremap time is not provided in stdout for only partially validated
>      regions. This time is only applicable for comparison if the entire
>      mapped region was faulted in.
>    - Use a random pattern for validating the remapped region. The -p
>      flag can be used to run the tests with a specified seed for the
>      random pattern.
>    - Print test configs (threshold_mb and pattern_seed) to stdout.
>    - Remove MAKE_SIMPLE_TEST macro.
>    - Define named flags instead of 0 / 1.
>    - Add comments for destination address' align_mask and offset.

Thanks for making those changes. This all looks much nicer, both in the
code and on the screen. Now it's easy to see which code generates which
output, and the tests are readable. The new comments are also helpful.

I ran it locally and it came in at 0.6 sec, so that looks good.

A remaining nit: there are lots of > 80 col lines here. Only those lines
that contain printf output strings really need to be extra-long. The
others can all be easily made to fit.

...
> +
> +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
> +#define MIN(X, Y) ((X) < (Y) ? (X) : (Y))


Not really a comment on this patch, but: at least two other test suites
in selftests/ have had to recreate MIN() or min(), and probably a few
other common things as well. It would be nice to gather up some of these
common things into one of the shared header files in selftests/.

I'm certainly not saying that this patchset has that responsibility,
though. Just pointing it out in case someone has a moment to clean up a
few here and there.

I'll assume that any changes to make things fit within 80 cols are
trivial, so you can add:

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
-- 
John Hubbard
NVIDIA

> +
> +struct config {
> +	unsigned long long src_alignment;
> +	unsigned long long dest_alignment;
> +	unsigned long long region_size;
> +	int overlapping;
> +};
> +
> +struct test {
> +	const char *name;
> +	struct config config;
> +	int expect_failure;
> +};
> +
> +enum {
> +	_1KB = 1ULL << 10,	/* 1KB -> not page aligned */
> +	_4KB = 4ULL << 10,
> +	_8KB = 8ULL << 10,
> +	_1MB = 1ULL << 20,
> +	_2MB = 2ULL << 20,
> +	_4MB = 4ULL << 20,
> +	_1GB = 1ULL << 30,
> +	_2GB = 2ULL << 30,
> +	PTE = _4KB,
> +	PMD = _2MB,
> +	PUD = _1GB,
> +};
> +
> +#define MAKE_TEST(source_align, destination_align, size,	\
> +		  overlaps, should_fail, test_name)		\
> +{								\
> +	.name = test_name,					\
> +	.config = {						\
> +		.src_alignment = source_align,			\
> +		.dest_alignment = destination_align,		\
> +		.region_size = size,				\
> +		.overlapping = overlaps,			\
> +	},							\
> +	.expect_failure = should_fail				\
> +}
> +
> +/*
> + * Returns the start address of the mapping on success, else returns
> + * NULL on failure.
> + */
> +static void *get_source_mapping(struct config c)
> +{
> +	unsigned long long addr = 0ULL;
> +	void *src_addr = NULL;
> +retry:
> +	addr += c.src_alignment;
> +	src_addr = mmap((void *) addr, c.region_size, PROT_READ | PROT_WRITE,
> +			MAP_FIXED | MAP_ANONYMOUS | MAP_SHARED, -1, 0);
> +	if (src_addr == MAP_FAILED) {
> +		if (errno == EPERM)
> +			goto retry;
> +		goto error;
> +	}
> +	/*
> +	 * Check that the address is aligned to the specified alignment. Addresses
> +	 * which have alignments that are multiples of that specified are not considered
> +	 * valid. For instance, 1GB address is 2MB-aligned, however it will not be
> +	 * considered valid for a requested alignment of 2MB. This is done to
> +	 * reduce coincidental alignment in the tests.
> +	 */
> +	if (((unsigned long long) src_addr & (c.src_alignment - 1)) ||
> +			!((unsigned long long) src_addr & c.src_alignment))
> +		goto retry;
> +
> +	if (!src_addr)
> +		goto error;
> +
> +	return src_addr;
> +error:
> +	ksft_print_msg("Failed to map source region: %s\n",
> +			strerror(errno));
> +	return NULL;
> +}
> +
> +/* Returns the time taken for the remap on success else returns -1. */
> +static long long remap_region(struct config c, unsigned int threshold_mb,
> +			      char pattern_seed)
> +{
> +	void *addr, *src_addr, *dest_addr;
> +	unsigned long long i;
> +	struct timespec t_start = {0, 0}, t_end = {0, 0};
> +	long long  start_ns, end_ns, align_mask, ret, offset;
> +	unsigned long long threshold;
> +
> +	if (threshold_mb == VALIDATION_NO_THRESHOLD)
> +		threshold = c.region_size;
> +	else
> +		threshold = MIN(threshold_mb * _1MB, c.region_size);
> +
> +	src_addr = get_source_mapping(c);
> +	if (!src_addr) {
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	/* Set byte pattern */
> +	srand(pattern_seed);
> +	for (i = 0; i < threshold; i++)
> +		memset((char *) src_addr + i, (char) rand(), 1);
> +
> +	/* Mask to zero out lower bits of address for alignment */
> +	align_mask = ~(c.dest_alignment - 1);
> +	/* Offset of destination address from the end of the source region */
> +	offset = (c.overlapping) ? -c.dest_alignment : c.dest_alignment;
> +	addr = (void *) (((unsigned long long) src_addr + c.region_size + offset)
> +			& align_mask);
> +
> +	/* See comment in get_source_mapping() */
> +	if (!((unsigned long long) addr & c.dest_alignment))
> +		addr = (void *) ((unsigned long long) addr | c.dest_alignment);
> +
> +	clock_gettime(CLOCK_MONOTONIC, &t_start);
> +	dest_addr = mremap(src_addr, c.region_size, c.region_size,
> +			MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
> +	clock_gettime(CLOCK_MONOTONIC, &t_end);
> +
> +	if (dest_addr == MAP_FAILED) {
> +		ksft_print_msg("mremap failed: %s\n", strerror(errno));
> +		ret = -1;
> +		goto clean_up_src;
> +	}
> +
> +	/* Verify byte pattern after remapping */
> +	srand(pattern_seed);
> +	for (i = 0; i < threshold; i++) {
> +		char c = (char) rand();
> +
> +		if (((char *) dest_addr)[i] != c) {
> +			ksft_print_msg("Data after remap doesn't match at offset %d\n",
> +					i);
> +			ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff,
> +					((char *) dest_addr)[i] & 0xff);
> +			ret = -1;
> +			goto clean_up_dest;
> +		}
> +	}
> +
> +	start_ns = t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec;
> +	end_ns = t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec;
> +	ret = end_ns - start_ns;
> +
> +/*
> + * Since the destination address is specified using MREMAP_FIXED, subsequent mremap will unmap any
> + * previous mapping at the address range specified by dest_addr and region_size. This significantly
> + * affects the remap time of subsequent tests. So we clean up mappings after each test.
> + */
> +clean_up_dest:
> +	munmap(dest_addr, c.region_size);
> +clean_up_src:
> +	munmap(src_addr, c.region_size);
> +out:
> +	return ret;
> +}
> +
> +static void run_mremap_test_case(struct test test_case, int *failures, unsigned int threshold_mb,
> +				 unsigned int pattern_seed)
> +{
> +	long long remap_time = remap_region(test_case.config, threshold_mb, pattern_seed);
> +
> +	if (remap_time < 0) {
> +		if (test_case.expect_failure)
> +			ksft_test_result_pass("%s\n\tExpected mremap failure\n", test_case.name);
> +		else {
> +			ksft_test_result_fail("%s\n", test_case.name);
> +			*failures += 1;
> +		}
> +	} else {
> +		/* Comparing mremap time is only applicable if entire region was faulted in */
> +		if (threshold_mb == VALIDATION_NO_THRESHOLD ||
> +		    test_case.config.region_size <= threshold_mb * _1MB)
> +			ksft_test_result_pass("%s\n\tmremap time: %12lldns\n",
> +					      test_case.name, remap_time);
> +		else
> +			ksft_test_result_pass("%s\n", test_case.name);
> +	}
> +}
> +
> +static void usage(const char *cmd)
> +{
> +	fprintf(stderr,
> +		"Usage: %s [[-t <threshold_mb>] [-p <pattern_seed>]]\n"
> +		"-t\t only validate threshold_mb of the remapped region\n"
> +		"  \t if 0 is supplied no threshold is used; all tests\n"
> +		"  \t are run and remapped regions validated fully.\n"
> +		"  \t The default threshold used is 4MB.\n"
> +		"-p\t provide a seed to generate the random pattern for\n"
> +		"  \t validating the remapped region.\n", cmd);
> +}
> +
> +static int parse_args(int argc, char **argv, unsigned int *threshold_mb,
> +		      unsigned int *pattern_seed)
> +{
> +	const char *optstr = "t:p:";
> +	int opt;
> +
> +	while ((opt = getopt(argc, argv, optstr)) != -1) {
> +		switch (opt) {
> +		case 't':
> +			*threshold_mb = atoi(optarg);
> +			break;
> +		case 'p':
> +			*pattern_seed = atoi(optarg);
> +			break;
> +		default:
> +			usage(argv[0]);
> +			return -1;
> +		}
> +	}
> +
> +	if (optind < argc) {
> +		usage(argv[0]);
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	int failures = 0;
> +	int i, run_perf_tests;
> +	unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD;
> +	unsigned int pattern_seed;
> +	time_t t;
> +
> +	pattern_seed = (unsigned int) time(&t);
> +
> +	if (parse_args(argc, argv, &threshold_mb, &pattern_seed) < 0)
> +		exit(EXIT_FAILURE);
> +
> +	ksft_print_msg("Test configs:\n\tthreshold_mb=%u\n\tpattern_seed=%u\n\n",
> +		       threshold_mb, pattern_seed);
> +
> +	struct test test_cases[] = {
> +		/* Expected mremap failures */
> +		MAKE_TEST(_4KB, _4KB, _4KB, OVERLAPPING, EXPECT_FAILURE,
> +			  "mremap - Source and Destination Regions Overlapping"),
> +		MAKE_TEST(_4KB, _1KB, _4KB, NON_OVERLAPPING, EXPECT_FAILURE,
> +			  "mremap - Destination Address Misaligned (1KB-aligned)"),
> +		MAKE_TEST(_1KB, _4KB, _4KB, NON_OVERLAPPING, EXPECT_FAILURE,
> +			  "mremap - Source Address Misaligned (1KB-aligned)"),
> +
> +		/* Src addr PTE aligned */
> +		MAKE_TEST(PTE, PTE, _8KB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "8KB mremap - Source PTE-aligned, Destination PTE-aligned"),
> +
> +		/* Src addr 1MB aligned */
> +		MAKE_TEST(_1MB, PTE, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "2MB mremap - Source 1MB-aligned, Destination PTE-aligned"),
> +		MAKE_TEST(_1MB, _1MB, _2MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "2MB mremap - Source 1MB-aligned, Destination 1MB-aligned"),
> +
> +		/* Src addr PMD aligned */
> +		MAKE_TEST(PMD, PTE, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "4MB mremap - Source PMD-aligned, Destination PTE-aligned"),
> +		MAKE_TEST(PMD, _1MB, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "4MB mremap - Source PMD-aligned, Destination 1MB-aligned"),
> +		MAKE_TEST(PMD, PMD, _4MB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "4MB mremap - Source PMD-aligned, Destination PMD-aligned"),
> +
> +		/* Src addr PUD aligned */
> +		MAKE_TEST(PUD, PTE, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "2GB mremap - Source PUD-aligned, Destination PTE-aligned"),
> +		MAKE_TEST(PUD, _1MB, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "2GB mremap - Source PUD-aligned, Destination 1MB-aligned"),
> +		MAKE_TEST(PUD, PMD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "2GB mremap - Source PUD-aligned, Destination PMD-aligned"),
> +		MAKE_TEST(PUD, PUD, _2GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "2GB mremap - Source PUD-aligned, Destination PUD-aligned"),
> +	};
> +
> +	struct test perf_test_cases[] = {
> +		/* mremap 1GB region - Page table level aligned time comparison */
> +		MAKE_TEST(PTE, PTE, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "1GB mremap - Source PTE-aligned, Destination PTE-aligned"),
> +		MAKE_TEST(PMD, PMD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "1GB mremap - Source PMD-aligned, Destination PMD-aligned"),
> +		MAKE_TEST(PUD, PUD, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
> +			  "1GB mremap - Source PUD-aligned, Destination PUD-aligned"),
> +	};
> +
> +	run_perf_tests =  (threshold_mb == VALIDATION_NO_THRESHOLD) ||
> +				(threshold_mb * _1MB >= _1GB);
> +
> +	ksft_set_plan(ARRAY_SIZE(test_cases) + (run_perf_tests ?
> +		      ARRAY_SIZE(perf_test_cases) : 0));
> +
> +	for (i = 0; i < ARRAY_SIZE(test_cases); i++)
> +		run_mremap_test_case(test_cases[i], &failures, threshold_mb, pattern_seed);
> +
> +	if (run_perf_tests) {
> +		ksft_print_msg("\n%s\n",
> +		 "mremap HAVE_MOVE_PMD/PUD optimization time comparison for 1GB region:");
> +		for (i = 0; i < ARRAY_SIZE(perf_test_cases); i++)
> +			run_mremap_test_case(perf_test_cases[i], &failures, threshold_mb,
> +					     pattern_seed);
> +	}
> +
> +	if (failures > 0)
> +		ksft_exit_fail();
> +	else
> +		ksft_exit_pass();
> +}
> diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
> index a3f4f30f0a2e..d578ad831813 100755
> --- a/tools/testing/selftests/vm/run_vmtests
> +++ b/tools/testing/selftests/vm/run_vmtests
> @@ -241,6 +241,17 @@ else
>   	echo "[PASS]"
>   fi
>   
> +echo "-------------------"
> +echo "running mremap_test"
> +echo "-------------------"
> +./mremap_test
> +if [ $? -ne 0 ]; then
> +	echo "[FAIL]"
> +	exitcode=1
> +else
> +	echo "[PASS]"
> +fi
> +
>   echo "-----------------"
>   echo "running thuge-gen"
>   echo "-----------------"
>