selftests/vm: add selftest to verify multi THP collapse

Add support to allocate and verify collapse of multiple hugepage-sized
regions into multiple THPs.

Add "nr" argument to check_huge() that instructs check_huge() to check for
exactly "nr_hpages" THPs.  This has the added benefit of now being able to
check for exactly 0 THPs, and so callsites that previously checked the
negation of exactly 1 THP are now more correct.

->collapse struct collapse_context hook has been expanded with a
"nr_hpages" argument to collapse "nr_hpages" hugepages.  The
collapse_full() test has been repurposed to collapse 4 THPs at once.  It
is expected more tests will want to test multi THP collapse (e.g. 
file/shmem).

This is of particular benefit to madvise collapse context given that it
may do many THP collapses during a single syscall.

Link: https://lkml.kernel.org/r/20220706235936.2197195-19-zokeefe@google.com
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 73 insertions, 67 deletions

diff --git a/tools/testing/selftests/vm/khugepaged.c b/tools/testing/selftests/vm/khugepaged.c
index 87cd0b99477f..b77b1e28cdb3 100644
--- a/tools/testing/selftests/vm/khugepaged.c
+++ b/tools/testing/selftests/vm/khugepaged.c
@@ -27,7 +27,7 @@ static int hpage_pmd_nr;
 #define PID_SMAPS "/proc/self/smaps"
 
 struct collapse_context {
-	void (*collapse)(const char *msg, char *p, bool expect);
+	void (*collapse)(const char *msg, char *p, int nr_hpages, bool expect);
 	bool enforce_pte_scan_limits;
 };
 
@@ -362,7 +362,7 @@ static bool check_for_pattern(FILE *fp, char *pattern, char *buf)
 	return false;
 }
 
-static bool check_huge(void *addr)
+static bool check_huge(void *addr, int nr_hpages)
 {
 	bool thp = false;
 	int ret;
@@ -387,7 +387,7 @@ static bool check_huge(void *addr)
 		goto err_out;
 
 	ret = snprintf(addr_pattern, MAX_LINE_LENGTH, "AnonHugePages:%10ld kB",
-		       hpage_pmd_size >> 10);
+		       nr_hpages * (hpage_pmd_size >> 10));
 	if (ret >= MAX_LINE_LENGTH) {
 		printf("%s: Pattern is too long\n", __func__);
 		exit(EXIT_FAILURE);
@@ -455,12 +455,12 @@ err_out:
 	return swap;
 }
 
-static void *alloc_mapping(void)
+static void *alloc_mapping(int nr)
 {
 	void *p;
 
-	p = mmap(BASE_ADDR, hpage_pmd_size, PROT_READ | PROT_WRITE,
-			MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	p = mmap(BASE_ADDR, nr * hpage_pmd_size, PROT_READ | PROT_WRITE,
+		 MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
 	if (p != BASE_ADDR) {
 		printf("Failed to allocate VMA at %p\n", BASE_ADDR);
 		exit(EXIT_FAILURE);
@@ -485,11 +485,11 @@ static void *alloc_hpage(void)
 {
 	void *p;
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 	printf("Allocate huge page...");
 	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
 	fill_memory(p, 0, hpage_pmd_size);
-	if (check_huge(p))
+	if (check_huge(p, 1))
 		success("OK");
 	else
 		fail("Fail");
@@ -509,14 +509,15 @@ static void validate_memory(int *p, unsigned long start, unsigned long end)
 	}
 }
 
-static void madvise_collapse(const char *msg, char *p, bool expect)
+static void madvise_collapse(const char *msg, char *p, int nr_hpages,
+			     bool expect)
 {
 	int ret;
 	struct settings settings = *current_settings();
 
 	printf("%s...", msg);
 	/* Sanity check */
-	if (check_huge(p)) {
+	if (!check_huge(p, 0)) {
 		printf("Unexpected huge page\n");
 		exit(EXIT_FAILURE);
 	}
@@ -529,11 +530,11 @@ static void madvise_collapse(const char *msg, char *p, bool expect)
 	push_settings(&settings);
 
 	/* Clear VM_NOHUGEPAGE */
-	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
-	ret = madvise(p, hpage_pmd_size, MADV_COLLAPSE);
+	madvise(p, nr_hpages * hpage_pmd_size, MADV_HUGEPAGE);
+	ret = madvise(p, nr_hpages * hpage_pmd_size, MADV_COLLAPSE);
 	if (((bool)ret) == expect)
 		fail("Fail: Bad return value");
-	else if (check_huge(p) != expect)
+	else if (check_huge(p, nr_hpages) != expect)
 		fail("Fail: check_huge()");
 	else
 		success("OK");
@@ -542,25 +543,25 @@ static void madvise_collapse(const char *msg, char *p, bool expect)
 }
 
 #define TICK 500000
-static bool wait_for_scan(const char *msg, char *p)
+static bool wait_for_scan(const char *msg, char *p, int nr_hpages)
 {
 	int full_scans;
 	int timeout = 6; /* 3 seconds */
 
 	/* Sanity check */
-	if (check_huge(p)) {
+	if (!check_huge(p, 0)) {
 		printf("Unexpected huge page\n");
 		exit(EXIT_FAILURE);
 	}
 
-	madvise(p, hpage_pmd_size, MADV_HUGEPAGE);
+	madvise(p, nr_hpages * hpage_pmd_size, MADV_HUGEPAGE);
 
 	/* Wait until the second full_scan completed */
 	full_scans = read_num("khugepaged/full_scans") + 2;
 
 	printf("%s...", msg);
 	while (timeout--) {
-		if (check_huge(p))
+		if (check_huge(p, nr_hpages))
 			break;
 		if (read_num("khugepaged/full_scans") >= full_scans)
 			break;
@@ -568,20 +569,21 @@ static bool wait_for_scan(const char *msg, char *p)
 		usleep(TICK);
 	}
 
-	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
+	madvise(p, nr_hpages * hpage_pmd_size, MADV_NOHUGEPAGE);
 
 	return timeout == -1;
 }
 
-static void khugepaged_collapse(const char *msg, char *p, bool expect)
+static void khugepaged_collapse(const char *msg, char *p, int nr_hpages,
+				bool expect)
 {
-	if (wait_for_scan(msg, p)) {
+	if (wait_for_scan(msg, p, nr_hpages)) {
 		if (expect)
 			fail("Timeout");
 		else
 			success("OK");
 		return;
-	} else if (check_huge(p) == expect) {
+	} else if (check_huge(p, nr_hpages) == expect) {
 		success("OK");
 	} else {
 		fail("Fail");
@@ -596,10 +598,10 @@ static void alloc_at_fault(void)
 	settings.thp_enabled = THP_ALWAYS;
 	push_settings(&settings);
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 	*p = 1;
 	printf("Allocate huge page on fault...");
-	if (check_huge(p))
+	if (check_huge(p, 1))
 		success("OK");
 	else
 		fail("Fail");
@@ -608,7 +610,7 @@ static void alloc_at_fault(void)
 
 	madvise(p, page_size, MADV_DONTNEED);
 	printf("Split huge PMD on MADV_DONTNEED...");
-	if (!check_huge(p))
+	if (check_huge(p, 0))
 		success("OK");
 	else
 		fail("Fail");
@@ -618,20 +620,23 @@ static void alloc_at_fault(void)
 static void collapse_full(struct collapse_context *c)
 {
 	void *p;
+	int nr_hpages = 4;
+	unsigned long size = nr_hpages * hpage_pmd_size;
 
-	p = alloc_mapping();
-	fill_memory(p, 0, hpage_pmd_size);
-	c->collapse("Collapse fully populated PTE table", p, true);
-	validate_memory(p, 0, hpage_pmd_size);
-	munmap(p, hpage_pmd_size);
+	p = alloc_mapping(nr_hpages);
+	fill_memory(p, 0, size);
+	c->collapse("Collapse multiple fully populated PTE table", p, nr_hpages,
+		    true);
+	validate_memory(p, 0, size);
+	munmap(p, size);
 }
 
 static void collapse_empty(struct collapse_context *c)
 {
 	void *p;
 
-	p = alloc_mapping();
-	c->collapse("Do not collapse empty PTE table", p, false);
+	p = alloc_mapping(1);
+	c->collapse("Do not collapse empty PTE table", p, 1, false);
 	munmap(p, hpage_pmd_size);
 }
 
@@ -639,10 +644,10 @@ static void collapse_single_pte_entry(struct collapse_context *c)
 {
 	void *p;
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 	fill_memory(p, 0, page_size);
 	c->collapse("Collapse PTE table with single PTE entry present", p,
-		    true);
+		    1, true);
 	validate_memory(p, 0, page_size);
 	munmap(p, hpage_pmd_size);
 }
@@ -656,16 +661,17 @@ static void collapse_max_ptes_none(struct collapse_context *c)
 	settings.khugepaged.max_ptes_none = max_ptes_none;
 	push_settings(&settings);
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 
 	fill_memory(p, 0, (hpage_pmd_nr - max_ptes_none - 1) * page_size);
-	c->collapse("Maybe collapse with max_ptes_none exceeded", p,
+	c->collapse("Maybe collapse with max_ptes_none exceeded", p, 1,
 		    !c->enforce_pte_scan_limits);
 	validate_memory(p, 0, (hpage_pmd_nr - max_ptes_none - 1) * page_size);
 
 	if (c->enforce_pte_scan_limits) {
 		fill_memory(p, 0, (hpage_pmd_nr - max_ptes_none) * page_size);
-		c->collapse("Collapse with max_ptes_none PTEs empty", p, true);
+		c->collapse("Collapse with max_ptes_none PTEs empty", p, 1,
+			    true);
 		validate_memory(p, 0,
 				(hpage_pmd_nr - max_ptes_none) * page_size);
 	}
@@ -677,7 +683,7 @@ static void collapse_max_ptes_none(struct collapse_context *c)
 static void collapse_swapin_single_pte(struct collapse_context *c)
 {
 	void *p;
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 	fill_memory(p, 0, hpage_pmd_size);
 
 	printf("Swapout one page...");
@@ -692,7 +698,7 @@ static void collapse_swapin_single_pte(struct collapse_context *c)
 		goto out;
 	}
 
-	c->collapse("Collapse with swapping in single PTE entry", p, true);
+	c->collapse("Collapse with swapping in single PTE entry", p, 1, true);
 	validate_memory(p, 0, hpage_pmd_size);
 out:
 	munmap(p, hpage_pmd_size);
@@ -703,7 +709,7 @@ static void collapse_max_ptes_swap(struct collapse_context *c)
 	int max_ptes_swap = read_num("khugepaged/max_ptes_swap");
 	void *p;
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 
 	fill_memory(p, 0, hpage_pmd_size);
 	printf("Swapout %d of %d pages...", max_ptes_swap + 1, hpage_pmd_nr);
@@ -718,7 +724,7 @@ static void collapse_max_ptes_swap(struct collapse_context *c)
 		goto out;
 	}
 
-	c->collapse("Maybe collapse with max_ptes_swap exceeded", p,
+	c->collapse("Maybe collapse with max_ptes_swap exceeded", p, 1,
 		    !c->enforce_pte_scan_limits);
 	validate_memory(p, 0, hpage_pmd_size);
 
@@ -738,7 +744,7 @@ static void collapse_max_ptes_swap(struct collapse_context *c)
 		}
 
 		c->collapse("Collapse with max_ptes_swap pages swapped out", p,
-			    true);
+			    1, true);
 		validate_memory(p, 0, hpage_pmd_size);
 	}
 out:
@@ -753,13 +759,13 @@ static void collapse_single_pte_entry_compound(struct collapse_context *c)
 	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
 	printf("Split huge page leaving single PTE mapping compound page...");
 	madvise(p + page_size, hpage_pmd_size - page_size, MADV_DONTNEED);
-	if (!check_huge(p))
+	if (check_huge(p, 0))
 		success("OK");
 	else
 		fail("Fail");
 
 	c->collapse("Collapse PTE table with single PTE mapping compound page",
-		    p, true);
+		    p, 1, true);
 	validate_memory(p, 0, page_size);
 	munmap(p, hpage_pmd_size);
 }
@@ -772,12 +778,12 @@ static void collapse_full_of_compound(struct collapse_context *c)
 	printf("Split huge page leaving single PTE page table full of compound pages...");
 	madvise(p, page_size, MADV_NOHUGEPAGE);
 	madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
-	if (!check_huge(p))
+	if (check_huge(p, 0))
 		success("OK");
 	else
 		fail("Fail");
 
-	c->collapse("Collapse PTE table full of compound pages", p, true);
+	c->collapse("Collapse PTE table full of compound pages", p, 1, true);
 	validate_memory(p, 0, hpage_pmd_size);
 	munmap(p, hpage_pmd_size);
 }
@@ -787,14 +793,14 @@ static void collapse_compound_extreme(struct collapse_context *c)
 	void *p;
 	int i;
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 	for (i = 0; i < hpage_pmd_nr; i++) {
 		printf("\rConstruct PTE page table full of different PTE-mapped compound pages %3d/%d...",
 				i + 1, hpage_pmd_nr);
 
 		madvise(BASE_ADDR, hpage_pmd_size, MADV_HUGEPAGE);
 		fill_memory(BASE_ADDR, 0, hpage_pmd_size);
-		if (!check_huge(BASE_ADDR)) {
+		if (!check_huge(BASE_ADDR, 1)) {
 			printf("Failed to allocate huge page\n");
 			exit(EXIT_FAILURE);
 		}
@@ -823,12 +829,12 @@ static void collapse_compound_extreme(struct collapse_context *c)
 
 	munmap(BASE_ADDR, hpage_pmd_size);
 	fill_memory(p, 0, hpage_pmd_size);
-	if (!check_huge(p))
+	if (check_huge(p, 0))
 		success("OK");
 	else
 		fail("Fail");
 
-	c->collapse("Collapse PTE table full of different compound pages", p,
+	c->collapse("Collapse PTE table full of different compound pages", p, 1,
 		    true);
 
 	validate_memory(p, 0, hpage_pmd_size);
@@ -840,11 +846,11 @@ static void collapse_fork(struct collapse_context *c)
 	int wstatus;
 	void *p;
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 
 	printf("Allocate small page...");
 	fill_memory(p, 0, page_size);
-	if (!check_huge(p))
+	if (check_huge(p, 0))
 		success("OK");
 	else
 		fail("Fail");
@@ -855,14 +861,14 @@ static void collapse_fork(struct collapse_context *c)
 		skip_settings_restore = true;
 		exit_status = 0;
 
-		if (!check_huge(p))
+		if (check_huge(p, 0))
 			success("OK");
 		else
 			fail("Fail");
 
 		fill_memory(p, page_size, 2 * page_size);
 		c->collapse("Collapse PTE table with single page shared with parent process",
-			    p, true);
+			    p, 1, true);
 
 		validate_memory(p, 0, page_size);
 		munmap(p, hpage_pmd_size);
@@ -873,7 +879,7 @@ static void collapse_fork(struct collapse_context *c)
 	exit_status += WEXITSTATUS(wstatus);
 
 	printf("Check if parent still has small page...");
-	if (!check_huge(p))
+	if (check_huge(p, 0))
 		success("OK");
 	else
 		fail("Fail");
@@ -893,7 +899,7 @@ static void collapse_fork_compound(struct collapse_context *c)
 		skip_settings_restore = true;
 		exit_status = 0;
 
-		if (check_huge(p))
+		if (check_huge(p, 1))
 			success("OK");
 		else
 			fail("Fail");
@@ -901,7 +907,7 @@ static void collapse_fork_compound(struct collapse_context *c)
 		printf("Split huge page PMD in child process...");
 		madvise(p, page_size, MADV_NOHUGEPAGE);
 		madvise(p, hpage_pmd_size, MADV_NOHUGEPAGE);
-		if (!check_huge(p))
+		if (check_huge(p, 0))
 			success("OK");
 		else
 			fail("Fail");
@@ -909,7 +915,7 @@ static void collapse_fork_compound(struct collapse_context *c)
 
 		write_num("khugepaged/max_ptes_shared", hpage_pmd_nr - 1);
 		c->collapse("Collapse PTE table full of compound pages in child",
-			    p, true);
+			    p, 1, true);
 		write_num("khugepaged/max_ptes_shared",
 			  current_settings()->khugepaged.max_ptes_shared);
 
@@ -922,7 +928,7 @@ static void collapse_fork_compound(struct collapse_context *c)
 	exit_status += WEXITSTATUS(wstatus);
 
 	printf("Check if parent still has huge page...");
-	if (check_huge(p))
+	if (check_huge(p, 1))
 		success("OK");
 	else
 		fail("Fail");
@@ -943,7 +949,7 @@ static void collapse_max_ptes_shared(struct collapse_context *c)
 		skip_settings_restore = true;
 		exit_status = 0;
 
-		if (check_huge(p))
+		if (check_huge(p, 1))
 			success("OK");
 		else
 			fail("Fail");
@@ -951,26 +957,26 @@ static void collapse_max_ptes_shared(struct collapse_context *c)
 		printf("Trigger CoW on page %d of %d...",
 				hpage_pmd_nr - max_ptes_shared - 1, hpage_pmd_nr);
 		fill_memory(p, 0, (hpage_pmd_nr - max_ptes_shared - 1) * page_size);
-		if (!check_huge(p))
+		if (check_huge(p, 0))
 			success("OK");
 		else
 			fail("Fail");
 
 		c->collapse("Maybe collapse with max_ptes_shared exceeded", p,
-			    !c->enforce_pte_scan_limits);
+			    1, !c->enforce_pte_scan_limits);
 
 		if (c->enforce_pte_scan_limits) {
 			printf("Trigger CoW on page %d of %d...",
 			       hpage_pmd_nr - max_ptes_shared, hpage_pmd_nr);
 			fill_memory(p, 0, (hpage_pmd_nr - max_ptes_shared) *
 				    page_size);
-			if (!check_huge(p))
+			if (check_huge(p, 0))
 				success("OK");
 			else
 				fail("Fail");
 
 			c->collapse("Collapse with max_ptes_shared PTEs shared",
-				    p, true);
+				    p, 1,  true);
 		}
 
 		validate_memory(p, 0, hpage_pmd_size);
@@ -982,7 +988,7 @@ static void collapse_max_ptes_shared(struct collapse_context *c)
 	exit_status += WEXITSTATUS(wstatus);
 
 	printf("Check if parent still has huge page...");
-	if (check_huge(p))
+	if (check_huge(p, 1))
 		success("OK");
 	else
 		fail("Fail");
@@ -995,7 +1001,7 @@ static void madvise_collapse_existing_thps(void)
 	void *p;
 	int err;
 
-	p = alloc_mapping();
+	p = alloc_mapping(1);
 	fill_memory(p, 0, hpage_pmd_size);
 
 	printf("Collapse fully populated PTE table...");
@@ -1005,11 +1011,11 @@ static void madvise_collapse_existing_thps(void)
 	 * MADV_COLLAPSE in "madvise" mode.
 	 */
 	err = madvise(p, hpage_pmd_size, MADV_COLLAPSE);
-	if (err == 0 && check_huge(p)) {
+	if (err == 0 && check_huge(p, 1)) {
 		success("OK");
 		printf("Re-collapse PMD-mapped hugepage");
 		err = madvise(p, hpage_pmd_size, MADV_COLLAPSE);
-		if (err == 0 && check_huge(p))
+		if (err == 0 && check_huge(p, 1))
 			success("OK");
 		else
 			fail("Fail");