Commit 391e8697 authored by Alexander Zhu's avatar Alexander Zhu Committed by Andrew Morton
Browse files

mm: selftest to verify zero-filled pages are mapped to zeropage 

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.

Link: https://lkml.kernel.org/r/20240830100438.3623486-4-usamaarif642@gmail.com


Signed-off-by: default avatarAlexander Zhu <alexlzhu@fb.com>
Signed-off-by: default avatarUsama Arif <usamaarif642@gmail.com>
Acked-by: default avatarRik van Riel <riel@surriel.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nico Pache <npache@redhat.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Shuang Zhai <zhais@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Shuang Zhai <szhai2@cs.rochester.edu>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b1f20206

tools/testing/selftests/mm/split_huge_page_test.c

+71 −0
Original line number Diff line number Diff line
@@ -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();

tools/testing/selftests/mm/vm_util.c

+22 −0
Original line number Diff line number Diff line
@@ -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)

{

tools/testing/selftests/mm/vm_util.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

unsigned long 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);