On 18/08/2024 22:30, Usama Arif wrote:
> From: Alexander Zhu <alexlzhu@xxxxxx>
>
> When a THP is split, any subpage that is zero-filled will be mapped
> to the shared zeropage, hence saving memory. Add selftest to verify
> this by allocating zero-filled THP and comparing RssAnon before and
> after split.
>
> Signed-off-by: Alexander Zhu <alexlzhu@xxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxxx>
> Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
> ---
> .../selftests/mm/split_huge_page_test.c | 71 +++++++++++++++++++
> tools/testing/selftests/mm/vm_util.c | 22 ++++++
> tools/testing/selftests/mm/vm_util.h | 1 +
> 3 files changed, 94 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
> index e5e8dafc9d94..eb6d1b9fc362 100644
> --- a/tools/testing/selftests/mm/split_huge_page_test.c
> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
> @@ -84,6 +84,76 @@ static void write_debugfs(const char *fmt, ...)
> write_file(SPLIT_DEBUGFS, input, ret + 1);
> }
>
> +static char *allocate_zero_filled_hugepage(size_t len)
> +{
> + char *result;
> + size_t i;
> +
> + result = memalign(pmd_pagesize, len);
> + if (!result) {
> + printf("Fail to allocate memory\n");
> + exit(EXIT_FAILURE);
> + }
> +
> + madvise(result, len, MADV_HUGEPAGE);
> +
> + for (i = 0; i < len; i++)
> + result[i] = (char)0;
> +
> + return result;
> +}
> +
> +static void verify_rss_anon_split_huge_page_all_zeroes(char *one_page, int nr_hpages, size_t len)
> +{
> + unsigned long rss_anon_before, rss_anon_after;
> + size_t i;
> +
> + if (!check_huge_anon(one_page, 4, pmd_pagesize)) {
> + printf("No THP is allocated\n");
> + exit(EXIT_FAILURE);
> + }
> +
> + rss_anon_before = rss_anon();
> + if (!rss_anon_before) {
> + printf("No RssAnon is allocated before split\n");
> + exit(EXIT_FAILURE);
> + }
> +
> + /* split all THPs */
> + write_debugfs(PID_FMT, getpid(), (uint64_t)one_page,
> + (uint64_t)one_page + len, 0);
> +
> + for (i = 0; i < len; i++)
> + if (one_page[i] != (char)0) {
> + printf("%ld byte corrupted\n", i);
> + exit(EXIT_FAILURE);
> + }
> +
> + if (!check_huge_anon(one_page, 0, pmd_pagesize)) {
> + printf("Still AnonHugePages not split\n");
> + exit(EXIT_FAILURE);
> + }
> +
> + rss_anon_after = rss_anon();
> + if (rss_anon_after >= rss_anon_before) {
> + printf("Incorrect RssAnon value. Before: %ld After: %ld\n",
> + rss_anon_before, rss_anon_after);
> + exit(EXIT_FAILURE);
> + }
> +}
> +
> +void split_pmd_zero_pages(void)
> +{
> + char *one_page;
> + int nr_hpages = 4;
> + size_t len = nr_hpages * pmd_pagesize;
> +
> + one_page = allocate_zero_filled_hugepage(len);
> + verify_rss_anon_split_huge_page_all_zeroes(one_page, nr_hpages, len);
> + printf("Split zero filled huge pages successful\n");
> + free(one_page);
> +}
> +
> void split_pmd_thp(void)
> {
> char *one_page;
> @@ -431,6 +501,7 @@ int main(int argc, char **argv)
>
> fd_size = 2 * pmd_pagesize;
>
> + split_pmd_zero_pages();
> split_pmd_thp();
> split_pte_mapped_thp();
> split_file_backed_thp();
> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> index 5a62530da3b5..d8d0cf04bb57 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -12,6 +12,7 @@
>
> #define PMD_SIZE_FILE_PATH "/sys/kernel/mm/transparent_hugepage/hpage_pmd_size"
> #define SMAP_FILE_PATH "/proc/self/smaps"
> +#define STATUS_FILE_PATH "/proc/self/status"
> #define MAX_LINE_LENGTH 500
>
> unsigned int __page_size;
> @@ -171,6 +172,27 @@ uint64_t read_pmd_pagesize(void)
> return strtoul(buf, NULL, 10);
> }
>
> +unsigned long rss_anon(void)
> +{
> + unsigned long rss_anon = 0;
> + FILE *fp;
> + char buffer[MAX_LINE_LENGTH];
> +
> + fp = fopen(STATUS_FILE_PATH, "r");
> + if (!fp)
> + ksft_exit_fail_msg("%s: Failed to open file %s\n", __func__, STATUS_FILE_PATH);
> +
> + if (!check_for_pattern(fp, "RssAnon:", buffer, sizeof(buffer)))
> + goto err_out;
> +
> + if (sscanf(buffer, "RssAnon:%10lu kB", &rss_anon) != 1)
> + ksft_exit_fail_msg("Reading status error\n");
> +
> +err_out:
> + fclose(fp);
> + return rss_anon;
> +}
> +
> bool __check_huge(void *addr, char *pattern, int nr_hpages,
> uint64_t hpage_size)
> {
> diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
> index 9007c420d52c..71b75429f4a5 100644
> --- a/tools/testing/selftests/mm/vm_util.h
> +++ b/tools/testing/selftests/mm/vm_util.h
> @@ -39,6 +39,7 @@ unsigned long pagemap_get_pfn(int fd, char *start);
> void clear_softdirty(void);
> bool check_for_pattern(FILE *fp, const char *pattern, char *buf, size_t len);
> uint64_t read_pmd_pagesize(void);
> +uint64_t rss_anon(void);
> bool check_huge_anon(void *addr, int nr_hpages, uint64_t hpage_size);
> bool check_huge_file(void *addr, int nr_hpages, uint64_t hpage_size);
> bool check_huge_shmem(void *addr, int nr_hpages, uint64_t hpage_size);
Need below fixlet as well
