[PATCH v5 12/19] selftests/mm: parameterize the mixed-source collapse case by source order

[Kiryl Shutsemau]

From: "Kiryl Shutsemau (Meta)" <kas@xxxxxxxxxx>

collapse_order_mixed_sources() faults its region as order-2 folios and
collapses them to the -c target.  Order 2 is below the contpte size on
every arm64 page size, so nothing in this suite collapses a contpte-mapped
source on purpose.

Let -s name the source order alongside -c.  The case then faults at that
order, keeping order 2 when -s is absent, and the source order has to be a
supported mTHP order below the target.  The other mTHP cases are
unaffected: mthp_push_target_order() enables only the target order.

"-s 5 -c 7" on arm64/64K then collapses contpte-mapped sources into a
larger mTHP.

Assisted-by: LLM
Acked-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
Tested-by: Muhammad Usama Anjum <usama.anjum@xxxxxxx>
Signed-off-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>
---
 tools/testing/selftests/mm/khugepaged.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
index fb4efaf67c40..b15cd07fc0b3 100644
--- a/tools/testing/selftests/mm/khugepaged.c
+++ b/tools/testing/selftests/mm/khugepaged.c
@@ -1352,11 +1352,13 @@ static void collapse_order_max_ptes_none(struct collapse_context *c,
 static void collapse_order_mixed_sources(struct collapse_context *c,
 					 struct mem_ops *ops)
 {
+	int source_order = anon_order ? anon_order : MIN_MTHP_ORDER;
 	struct thp_settings settings;
 	void *p;
 
-	if (collapse_order <= MIN_MTHP_ORDER) {
-		ksft_test_result_skip("%s: no source order below target\n",
+	if (source_order >= collapse_order ||
+	    !(thp_supported_orders() & (1UL << source_order))) {
+		ksft_test_result_skip("%s: no supported source order below target\n",
 				      __func__);
 		return;
 	}
@@ -1364,7 +1366,7 @@ static void collapse_order_mixed_sources(struct collapse_context *c,
 	mthp_push_target_order();
 
 	settings = *thp_current_settings();
-	settings.hugepages[MIN_MTHP_ORDER].enabled = THP_ALWAYS;
+	settings.hugepages[source_order].enabled = THP_ALWAYS;
 	thp_push_settings(&settings);
 	p = ops->setup_area(1);
 	ops->fault(p, 0, hpage_pmd_size);
@@ -1374,10 +1376,9 @@ static void collapse_order_mixed_sources(struct collapse_context *c,
 	 * The allocator can fall back to smaller folios under fragmentation;
 	 * having nothing to collapse from is not a failure.
 	 */
-	if (!is_range_backed_by_order(p, hpage_pmd_size, MIN_MTHP_ORDER,
+	if (!is_range_backed_by_order(p, hpage_pmd_size, source_order,
 				      pagemap_fd, kpageflags_fd)) {
-		ksft_print_msg("No order-%d sources to collapse...",
-			       MIN_MTHP_ORDER);
+		ksft_print_msg("No order-%d sources to collapse...", source_order);
 		skip("Skip");
 		ops->cleanup_area(p, hpage_pmd_size);
 		thp_pop_settings();
@@ -1387,7 +1388,8 @@ static void collapse_order_mixed_sources(struct collapse_context *c,
 
 	if (madvise(p, hpage_pmd_size, MADV_HUGEPAGE))
 		ksft_exit_fail_perror("madvise(MADV_HUGEPAGE)");
-	ksft_print_msg("Collapse region backed by smaller large folios...");
+	ksft_print_msg("Collapse region backed by order-%d sources...",
+		       source_order);
 	if (!khugepaged_full_pass(MTHP_PASS_TIMEOUT_S))
 		fail("Timeout");
 	else if (all_windows_at_order(p, hpage_pmd_size))
@@ -1418,6 +1420,7 @@ static void usage(void)
 	fprintf(stderr,	"\t\t-s: mTHP size, expressed as page order.\n");
 	fprintf(stderr,	"\t\t    Defaults to 0. Use this size for anon or shmem allocations.\n");
 	fprintf(stderr,	"\t\t-c: collapse order for mTHP collapse, expressed as page order.\n");
+	fprintf(stderr,	"\t\t    -s, if set, is the source order for the mixed-source case.\n");
 	exit(1);
 }
 
-- 
2.54.0