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Date: Mon, 16 Aug 2021 09:00:07 -0500
From: Tyler Hicks <tyhicks@...ux.microsoft.com>
To: Zhansaya Bagdauletkyzy <zhansayabagdaulet@...il.com>
Cc: shuah@...nel.org, akpm@...ux-foundation.org,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-mm@...ck.org, pasha.tatashin@...een.com
Subject: Re: [PATCH v2 3/4] selftests: vm: add KSM zero page merging test
On 2021-07-14 14:56:14, Zhansaya Bagdauletkyzy wrote:
> Add check_ksm_zero_page_merge() function to test that empty pages are
> being handled properly. For this, several zero pages are allocated and
> merged using madvise. If use_zero_pages is enabled, the pages must be
> shared with the special kernel zero pages; otherwise, they are merged
> as usual duplicate pages. The test is run as follows: ./ksm_tests -Z
>
> Signed-off-by: Zhansaya Bagdauletkyzy <zhansayabagdaulet@...il.com>
Reviewed-by: Tyler Hicks <tyhicks@...ux.microsoft.com>
Tyler
> ---
> tools/testing/selftests/vm/ksm_tests.c | 70 ++++++++++++++++++++++-
> tools/testing/selftests/vm/run_vmtests.sh | 32 +++++++++++
> 2 files changed, 99 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
> index 80302bb8f64c..5843526471e1 100644
> --- a/tools/testing/selftests/vm/ksm_tests.c
> +++ b/tools/testing/selftests/vm/ksm_tests.c
> @@ -12,6 +12,7 @@
> #define KSM_SCAN_LIMIT_SEC_DEFAULT 120
> #define KSM_PAGE_COUNT_DEFAULT 10l
> #define KSM_PROT_STR_DEFAULT "rw"
> +#define KSM_USE_ZERO_PAGES_DEFAULT false
>
> struct ksm_sysfs {
> unsigned long max_page_sharing;
> @@ -25,7 +26,8 @@ struct ksm_sysfs {
>
> enum ksm_test_name {
> CHECK_KSM_MERGE,
> - CHECK_KSM_UNMERGE
> + CHECK_KSM_UNMERGE,
> + CHECK_KSM_ZERO_PAGE_MERGE
> };
>
> static int ksm_write_sysfs(const char *file_path, unsigned long val)
> @@ -80,10 +82,12 @@ static int str_to_prot(char *prot_str)
>
> static void print_help(void)
> {
> - printf("usage: ksm_tests [-h] <test type> [-a prot] [-p page_count] [-l timeout]\n");
> + printf("usage: ksm_tests [-h] <test type> [-a prot] [-p page_count] [-l timeout]\n"
> + "[-z use_zero_pages]\n");
>
> printf("Supported <test type>:\n"
> " -M (page merging)\n"
> + " -Z (zero pages merging)\n"
> " -U (page unmerging)\n\n");
>
> printf(" -a: specify the access protections of pages.\n"
> @@ -93,6 +97,8 @@ static void print_help(void)
> " Default: %ld\n", KSM_PAGE_COUNT_DEFAULT);
> printf(" -l: limit the maximum running time (in seconds) for a test.\n"
> " Default: %d seconds\n", KSM_SCAN_LIMIT_SEC_DEFAULT);
> + printf(" -z: change use_zero_pages tunable\n"
> + " Default: %d\n", KSM_USE_ZERO_PAGES_DEFAULT);
>
> exit(0);
> }
> @@ -289,6 +295,50 @@ static int check_ksm_unmerge(int mapping, int prot, int timeout, size_t page_siz
> return KSFT_FAIL;
> }
>
> +static int check_ksm_zero_page_merge(int mapping, int prot, long page_count, int timeout,
> + bool use_zero_pages, size_t page_size)
> +{
> + void *map_ptr;
> + struct timespec start_time;
> +
> + if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
> + perror("clock_gettime");
> + return KSFT_FAIL;
> + }
> +
> + if (ksm_write_sysfs(KSM_FP("use_zero_pages"), use_zero_pages))
> + return KSFT_FAIL;
> +
> + /* fill pages with zero and try to merge them */
> + map_ptr = allocate_memory(NULL, prot, mapping, 0, page_size * page_count);
> + if (!map_ptr)
> + return KSFT_FAIL;
> +
> + if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
> + goto err_out;
> +
> + /*
> + * verify that the right number of pages are merged:
> + * 1) if use_zero_pages is set to 1, empty pages are merged
> + * with the kernel zero page instead of with each other;
> + * 2) if use_zero_pages is set to 0, empty pages are not treated specially
> + * and merged as usual.
> + */
> + if (use_zero_pages && !assert_ksm_pages_count(0))
> + goto err_out;
> + else if (!use_zero_pages && !assert_ksm_pages_count(page_count))
> + goto err_out;
> +
> + printf("OK\n");
> + munmap(map_ptr, page_size * page_count);
> + return KSFT_PASS;
> +
> +err_out:
> + printf("Not OK\n");
> + munmap(map_ptr, page_size * page_count);
> + return KSFT_FAIL;
> +}
> +
> int main(int argc, char *argv[])
> {
> int ret, opt;
> @@ -298,8 +348,9 @@ int main(int argc, char *argv[])
> size_t page_size = sysconf(_SC_PAGESIZE);
> struct ksm_sysfs ksm_sysfs_old;
> int test_name = CHECK_KSM_MERGE;
> + bool use_zero_pages = KSM_USE_ZERO_PAGES_DEFAULT;
>
> - while ((opt = getopt(argc, argv, "ha:p:l:MU")) != -1) {
> + while ((opt = getopt(argc, argv, "ha:p:l:z:MUZ")) != -1) {
> switch (opt) {
> case 'a':
> prot = str_to_prot(optarg);
> @@ -321,11 +372,20 @@ int main(int argc, char *argv[])
> case 'h':
> print_help();
> break;
> + case 'z':
> + if (strcmp(optarg, "0") == 0)
> + use_zero_pages = 0;
> + else
> + use_zero_pages = 1;
> + break;
> case 'M':
> break;
> case 'U':
> test_name = CHECK_KSM_UNMERGE;
> break;
> + case 'Z':
> + test_name = CHECK_KSM_ZERO_PAGE_MERGE;
> + break;
> default:
> return KSFT_FAIL;
> }
> @@ -359,6 +419,10 @@ int main(int argc, char *argv[])
> ret = check_ksm_unmerge(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
> page_size);
> break;
> + case CHECK_KSM_ZERO_PAGE_MERGE:
> + ret = check_ksm_zero_page_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count,
> + ksm_scan_limit_sec, use_zero_pages, page_size);
> + break;
> }
>
> if (ksm_restore(&ksm_sysfs_old)) {
> diff --git a/tools/testing/selftests/vm/run_vmtests.sh b/tools/testing/selftests/vm/run_vmtests.sh
> index 3a23c6b47da2..9b4e444fc4ed 100755
> --- a/tools/testing/selftests/vm/run_vmtests.sh
> +++ b/tools/testing/selftests/vm/run_vmtests.sh
> @@ -409,6 +409,38 @@ else
> exitcode=1
> fi
>
> +echo "----------------------------------------------------------"
> +echo "running KSM test with 10 zero pages and use_zero_pages = 0"
> +echo "----------------------------------------------------------"
> +./ksm_tests -Z -p 10 -z 0
> +ret_val=$?
> +
> +if [ $ret_val -eq 0 ]; then
> + echo "[PASS]"
> +elif [ $ret_val -eq $ksft_skip ]; then
> + echo "[SKIP]"
> + exitcode=$ksft_skip
> +else
> + echo "[FAIL]"
> + exitcode=1
> +fi
> +
> +echo "----------------------------------------------------------"
> +echo "running KSM test with 10 zero pages and use_zero_pages = 1"
> +echo "----------------------------------------------------------"
> +./ksm_tests -Z -p 10 -z 1
> +ret_val=$?
> +
> +if [ $ret_val -eq 0 ]; then
> + echo "[PASS]"
> +elif [ $ret_val -eq $ksft_skip ]; then
> + echo "[SKIP]"
> + exitcode=$ksft_skip
> +else
> + echo "[FAIL]"
> + exitcode=1
> +fi
> +
> exit $exitcode
>
> exit $exitcode
> --
> 2.25.1
>
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