+ selftests-mm-compaction_test-support-platform-with-huge-mount-of-memory.patch added to mm-hotfixes-unstable branch

+ selftests-mm-compaction_test-support-platform-with-huge-mount-of-memory.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: selftests/mm: compaction_test: support platform with huge mount of memory
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     selftests-mm-compaction_test-support-platform-with-huge-mount-of-memory.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-compaction_test-support-platform-with-huge-mount-of-memory.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Feng Tang <feng.tang@linux.alibaba.com>
Subject: selftests/mm: compaction_test: support platform with huge mount of memory
Date: Wed, 23 Apr 2025 18:36:45 +0800

When running mm selftest to verify mm patches, 'compaction_test' case
failed on an x86 server with 1TB memory.  And the root cause is that it
has too much free memory than what the test supports.

The test case tries to allocate 100000 huge pages, which is about 200 GB
for that x86 server, and when it succeeds, it expects it's large than 1/3
of 80% of the free memory in system.  This logic only works for platform
with 750 GB ( 200 / (1/3) / 80% ) or less free memory, and may raise false
alarm for others.

Fix it by changing the fixed page number to self-adjustable number
according to the real number of free memory.

Link: https://lkml.kernel.org/r/20250423103645.2758-1-feng.tang@linux.alibaba.com
Fixes: bd67d5c15cc19 ("Test compaction of mlocked memory")
Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>
Acked-by: Dev Jain <dev.jain@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Sri Jayaramappa <sjayaram@akamai.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 tools/testing/selftests/mm/compaction_test.c |   19 ++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

--- a/tools/testing/selftests/mm/compaction_test.c~selftests-mm-compaction_test-support-platform-with-huge-mount-of-memory
+++ a/tools/testing/selftests/mm/compaction_test.c
@@ -90,6 +90,8 @@ int check_compaction(unsigned long mem_f
 	int compaction_index = 0;
 	char nr_hugepages[20] = {0};
 	char init_nr_hugepages[24] = {0};
+	char target_nr_hugepages[24] = {0};
+	int slen;
 
 	snprintf(init_nr_hugepages, sizeof(init_nr_hugepages),
 		 "%lu", initial_nr_hugepages);
@@ -106,11 +108,18 @@ int check_compaction(unsigned long mem_f
 		goto out;
 	}
 
-	/* Request a large number of huge pages. The Kernel will allocate
-	   as much as it can */
-	if (write(fd, "100000", (6*sizeof(char))) != (6*sizeof(char))) {
-		ksft_print_msg("Failed to write 100000 to /proc/sys/vm/nr_hugepages: %s\n",
-			       strerror(errno));
+	/*
+	 * Request huge pages for about half of the free memory. The Kernel
+	 * will allocate as much as it can, and we expect it will get at least 1/3
+	 */
+	nr_hugepages_ul = mem_free / hugepage_size / 2;
+	snprintf(target_nr_hugepages, sizeof(target_nr_hugepages),
+		 "%lu", nr_hugepages_ul);
+
+	slen = strlen(target_nr_hugepages);
+	if (write(fd, target_nr_hugepages, slen) != slen) {
+		ksft_print_msg("Failed to write %lu to /proc/sys/vm/nr_hugepages: %s\n",
+			       nr_hugepages_ul, strerror(errno));
 		goto close_fd;
 	}
 
_

Patches currently in -mm which might be from feng.tang@linux.alibaba.com are

selftests-mm-compaction_test-support-platform-with-huge-mount-of-memory.patch