[merged mm-stable] selftests-mm-add-memory-pressure-threads-to-the-khugepaged-race-harness.patch removed from -mm tree

[merged mm-stable] selftests-mm-add-memory-pressure-threads-to-the-khugepaged-race-harness.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: selftests/mm: add memory-pressure threads to the khugepaged race harness
has been removed from the -mm tree.  Its filename was
     selftests-mm-add-memory-pressure-threads-to-the-khugepaged-race-harness.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "Kiryl Shutsemau (Meta)" <kas@kernel.org>
Subject: selftests/mm: add memory-pressure threads to the khugepaged race harness
Date: Sat, 19 Sep 2026 01:24:48 +0100

The harness races collapse against faults, pins, fork, mremap and
MADV_DONTNEED, but nothing in it runs reclaim or compaction against the
collapse.

Add two more threads, and run every mode and occupancy limit both with and
without them:

 - pageout: cycles MADV_PAGEOUT over a region of its own, faults it back
   in and checks the content each round, since a page's pattern must
   survive the trip through swap.  Left out when the host has no swap,
   because then there is no anon reclaim to drive.

 - compactor: writes /proc/sys/vm/compact_memory in a loop.  Compaction
   isolates and migrates folios, so it competes with a collapse for the
   pages it is gathering, with refcount elevations and migration entries
   of its own.

Each result says whether it ran under pressure:

  ok 2 stepped/strict/pressure: 5s, 88 steps, no corruption

A full run is now twelve combinations; -m picks one mode, -d shortens
each run.

Link: https://lore.kernel.org/20260919002451.496763-19-kirill@shutemov.name
Signed-off-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Assisted-by: LLM
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: "David Hildenbrand (arm)" <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickens <hughd@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: kernel-team@meta.com
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Liam Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Nico Pache (Red Hat) <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan (Samsung OSG) <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
---

 tools/testing/selftests/mm/khugepaged_race.c |  142 ++++++++++++++---
 1 file changed, 122 insertions(+), 20 deletions(-)

--- a/tools/testing/selftests/mm/khugepaged_race.c~selftests-mm-add-memory-pressure-threads-to-the-khugepaged-race-harness
+++ a/tools/testing/selftests/mm/khugepaged_race.c
@@ -44,6 +44,8 @@ static unsigned long page_size;
 static char *region;
 static char *mremap_area;
 static char *mremap_scratch;
+static char *pageout_area;
+static size_t pageout_size;
 static int gup_fd = -1;
 static volatile int stop;
 static volatile int corrupted;
@@ -204,6 +206,69 @@ static void *mremapper_fn(void *arg)
 	return NULL;
 }
 
+/*
+ * Swap traffic and LRU churn on a region nothing else writes, so a page's
+ * pattern must survive the trip through swap exactly.
+ */
+static void *pageout_fn(void *arg)
+{
+	unsigned int seed = (unsigned long)arg;
+	unsigned long nr = pageout_size / page_size;
+	unsigned long i;
+
+	for (i = 0; i < nr; i++)
+		*(unsigned int *)(pageout_area + i * page_size) = pattern(i);
+
+	while (!stop) {
+		madvise(pageout_area, pageout_size, MADV_PAGEOUT);
+		for (i = 0; i < nr && !stop; i++) {
+			unsigned int val = *(unsigned int *)(pageout_area +
+							     i * page_size);
+
+			if (val != pattern(i)) {
+				corrupted = 1;
+				ksft_print_msg("Pageout corruption at page %lu: %#x != %#x\n",
+					       i, val, pattern(i));
+			}
+		}
+		usleep(rand_r(&seed) % 2000);
+	}
+	return NULL;
+}
+
+/* Compaction migrates the collapse sources while they are being gathered */
+static void *compactor_fn(void *arg)
+{
+	unsigned int seed = (unsigned long)arg;
+	int fd = open("/proc/sys/vm/compact_memory", O_WRONLY);
+
+	if (fd < 0) {
+		ksft_print_msg("No compact_memory; compactor idle\n");
+		return NULL;
+	}
+	while (!stop) {
+		if (write(fd, "1", 1) < 0)
+			break;
+		usleep(10000 + rand_r(&seed) % 100000);
+	}
+	close(fd);
+	return NULL;
+}
+
+static bool swap_available(void)
+{
+	char line[256];
+	int lines = 0;
+	FILE *fp = fopen("/proc/swaps", "r");
+
+	if (!fp)
+		return false;
+	while (fgets(line, sizeof(line), fp))
+		lines++;
+	fclose(fp);
+	return lines > 1;
+}
+
 static unsigned long now_ms(void)
 {
 	struct timeval tv;
@@ -227,17 +292,23 @@ int main(int argc, char **argv)
 {
 	static const char * const thread_names[] = {
 		"faulter", "faulter2", "dontneed", "pinner", "forker",
-		"mremapper",
+		"mremapper", "pageout", "compactor",
 	};
 	void *(*const thread_fns[])(void *) = {
 		faulter_fn, faulter_fn, dontneed_fn, pinner_fn, forker_fn,
-		mremapper_fn,
+		mremapper_fn, pageout_fn, compactor_fn,
 	};
+	enum { T_FAULTER, T_FAULTER2, T_DONTNEED, T_PINNER, T_FORKER,
+	       T_MREMAPPER, T_PAGEOUT, T_COMPACTOR };
+	const unsigned long pageout_bit = 1UL << T_PAGEOUT;
+	const unsigned long compactor_bit = 1UL << T_COMPACTOR;
 	const int nr_threads = ARRAY_SIZE(thread_names);
 	pthread_t threads[ARRAY_SIZE(thread_names)];
 	static const char * const all_modes[] = { "stepped", "free", "madvise" };
 	static const bool occupancies[] = { false, true };	/* strict, holes */
+	static const bool pressures[] = { false, true };	/* quiet, under pressure */
 	const int nr_occupancies = ARRAY_SIZE(occupancies);
+	const int nr_pressures = ARRAY_SIZE(pressures);
 	const char *one_mode[1];
 	const char * const *modes = all_modes;
 	int nr_modes = ARRAY_SIZE(all_modes);
@@ -246,6 +317,9 @@ int main(int argc, char **argv)
 	unsigned long end_ms;
 	int duration_s = 5;
 	unsigned long thread_mask = ~0UL;
+	unsigned long base_mask;
+	bool have_swap;
+	char label[64];
 	int nr_areas_arg = 0;
 	unsigned long i;
 	int steps = 0;
@@ -305,7 +379,13 @@ int main(int argc, char **argv)
 		 -1, 0) != (void *)mremap_scratch)
 		ksft_exit_fail_perror("mmap() mremap scratch");
 
-	ksft_set_plan(nr_modes * nr_occupancies);
+	base_mask = thread_mask;
+	have_swap = swap_available();
+	if (!have_swap)
+		/* No swap, no anon reclaim: compaction-only pressure */
+		ksft_print_msg("no swap: the pageout thread is not started\n");
+
+	ksft_set_plan(nr_modes * nr_occupancies * nr_pressures);
 
 	thp_save_settings();
 	thp_read_settings(&settings);
@@ -313,9 +393,25 @@ int main(int argc, char **argv)
 	/* Base of the settings stack; the bottom entry is never popped */
 	thp_push_settings(&settings);
 
-	for (int run = 0; run < nr_modes * nr_occupancies; run++) {
-		const char *mode = modes[run / nr_occupancies];
-		bool holes = occupancies[run % nr_occupancies];
+	for (int run = 0; run < nr_modes * nr_occupancies * nr_pressures; run++) {
+		int rem = run % (nr_occupancies * nr_pressures);
+		const char *mode = modes[run / (nr_occupancies * nr_pressures)];
+		bool holes = occupancies[rem / nr_pressures];
+		bool pressure = pressures[rem % nr_pressures];
+
+		snprintf(label, sizeof(label), "%s/%s%s", mode,
+			 holes ? "holes" : "strict", pressure ? "/pressure" : "");
+		if (corrupted) {
+			/* Memory is suspect; the rest would prove nothing */
+			ksft_test_result_skip("%s: skipped after corruption\n", label);
+			continue;
+		}
+
+		thread_mask = base_mask;
+		if (!pressure)
+			thread_mask &= ~(pageout_bit | compactor_bit);
+		else if (!have_swap)
+			thread_mask &= ~pageout_bit;
 
 		thp_read_settings(&settings);
 		settings.thp_enabled = THP_MADVISE;
@@ -349,6 +445,20 @@ int main(int argc, char **argv)
 			ksft_exit_fail_perror("mmap() playground");
 		mremap_area = region + nr_shared_areas * hpage_pmd_size;
 
+		if (thread_mask & pageout_bit) {
+			/* Enough to drive real reclaim without swamping a small guest */
+			pageout_size = 4 * hpage_pmd_size;
+			if (pageout_size < 16UL << 20)
+				pageout_size = 16UL << 20;
+			if (pageout_size > 64UL << 20)
+				pageout_size = 64UL << 20;
+			pageout_area = mmap(NULL, pageout_size,
+					    PROT_READ | PROT_WRITE,
+					    MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+			if (pageout_area == MAP_FAILED)
+				ksft_exit_fail_perror("mmap() pageout area");
+		}
+
 		/* Populate so the first pass has something to collapse */
 		for (i = 0; i < nr_shared_areas * hpage_pmd_size / page_size; i++)
 			*(unsigned int *)(region + i * page_size) = pattern(i);
@@ -397,26 +507,18 @@ int main(int argc, char **argv)
 		for (i = 0; i < nr_shared_areas * hpage_pmd_size / page_size; i++)
 			check_page(i);
 
-		ksft_test_result(!corrupted,
-				 "%s/%s: %ds, %d steps, no corruption\n",
-				 mode, holes ? "holes" : "strict",
-				 duration_s, steps);
+		ksft_test_result(!corrupted, "%s: %ds, %d steps, no corruption\n",
+				 label, duration_s, steps);
 
 		/* The next mode maps the same fixed address with its own settings */
 		munmap(region, nr_areas * hpage_pmd_size);
+		if (pageout_area) {
+			munmap(pageout_area, pageout_size);
+			pageout_area = NULL;
+		}
 		thp_pop_settings();
 		stop = 0;
 		steps = 0;
-
-		if (corrupted) {
-			/* Memory is suspect; the rest would prove nothing */
-			while (++run < nr_modes * nr_occupancies)
-				ksft_test_result_skip("%s/%s: skipped after corruption\n",
-						      modes[run / nr_occupancies],
-						      occupancies[run % nr_occupancies] ?
-						      "holes" : "strict");
-			break;
-		}
 	}
 
 	ksft_finished();
_

Patches currently in -mm which might be from kas@kernel.org are

mm-page_alloc-make-defrag_mode-retries-follow-the-promoted-order.patch
mm-khugepaged-drop-redundant-mm_struct-pin-in-madvise_collapse.patch
mm-khugepaged-count-collapses-where-khugepaged-makes-them.patch
mm-khugepaged-rename-mthp_present_ptes-bitmap-to-eligible_ptes.patch
mm-collapse-add-collapseh-for-the-collapse-interface.patch
mm-collapse-state-what-a-collapse-may-do-in-the-policy.patch
mm-collapse-drop-the-collapse_possible-wrapper.patch
mm-collapse-name-the-per-table-scan-reset-for-what-it-resets.patch
mm-collapse-call-collapse_file-from-collapse_single_pmd.patch
mm-collapse-separate-scanning-a-pte-table-from-collapsing-it.patch
mm-collapse-open-code-collapse_single_pmd-in-its-two-callers.patch
mm-collapse-work-out-the-orders-a-vma-allows-once-per-vma.patch
mm-collapse-declare-the-collapse-interface-in-collapseh.patch
mm-collapse-implement-madv_collapse-in-madvisec.patch