lib/test_vmalloc.c: minor fixes to test_vmalloc.c

If PAGE_SIZE is larger than 4k and if you have a system with a large
number of CPUs, this test can require a very large amount of memory
leading to oom-killer firing.  Given the type of allocation, the kernel
won't have anything to kill, causing the system to stall.

Add a parameter to the test_vmalloc driver to represent the number of
times a percpu object will be allocated.  Calculate this in
test_vmalloc.sh to be 90% of available memory or the current default of
35000, whichever is smaller.

Link: https://lkml.kernel.org/r/20251201181848.1216197-1-audra@redhat.com
Signed-off-by: Audra Mitchell <audra@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 28 insertions, 3 deletions

diff --git a/tools/testing/selftests/mm/test_vmalloc.sh b/tools/testing/selftests/mm/test_vmalloc.sh
index d39096723fca..b23d705bf570 100755
--- a/tools/testing/selftests/mm/test_vmalloc.sh
+++ b/tools/testing/selftests/mm/test_vmalloc.sh
@@ -13,6 +13,9 @@ TEST_NAME="vmalloc"
 DRIVER="test_${TEST_NAME}"
 NUM_CPUS=`grep -c ^processor /proc/cpuinfo`
 
+# Default number of times we allocate percpu objects:
+NR_PCPU_OBJECTS=35000
+
 # 1 if fails
 exitcode=1
 
@@ -27,6 +30,8 @@ PERF_PARAM="sequential_test_order=1 test_repeat_count=3"
 SMOKE_PARAM="test_loop_count=10000 test_repeat_count=10"
 STRESS_PARAM="nr_threads=$NUM_CPUS test_repeat_count=20"
 
+PCPU_OBJ_PARAM="nr_pcpu_objects=$NR_PCPU_OBJECTS"
+
 check_test_requirements()
 {
 	uid=$(id -u)
@@ -47,12 +52,30 @@ check_test_requirements()
 	fi
 }
 
+check_memory_requirement()
+{
+	# The pcpu_alloc_test allocates nr_pcpu_objects per cpu. If the
+	# PAGE_SIZE is on the larger side it is easier to set a value
+	# that can cause oom events during testing. Since we are
+	# testing the functionality of vmalloc and not the oom-killer,
+	# calculate what is 90% of available memory and divide it by
+	# the number of online CPUs.
+	pages=$(($(getconf _AVPHYS_PAGES) * 90 / 100 / $NUM_CPUS))
+
+	if (($pages < $NR_PCPU_OBJECTS)); then
+		echo "Updated nr_pcpu_objects to 90% of available memory."
+		echo "nr_pcpu_objects is now set to: $pages."
+		PCPU_OBJ_PARAM="nr_pcpu_objects=$pages"
+	fi
+}
+
 run_performance_check()
 {
 	echo "Run performance tests to evaluate how fast vmalloc allocation is."
 	echo "It runs all test cases on one single CPU with sequential order."
 
-	modprobe $DRIVER $PERF_PARAM > /dev/null 2>&1
+	check_memory_requirement
+	modprobe $DRIVER $PERF_PARAM $PCPU_OBJ_PARAM > /dev/null 2>&1
 	echo "Done."
 	echo "Check the kernel message buffer to see the summary."
 }
@@ -63,7 +86,8 @@ run_stability_check()
 	echo "available test cases are run by NUM_CPUS workers simultaneously."
 	echo "It will take time, so be patient."
 
-	modprobe $DRIVER $STRESS_PARAM > /dev/null 2>&1
+	check_memory_requirement
+	modprobe $DRIVER $STRESS_PARAM $PCPU_OBJ_PARAM > /dev/null 2>&1
 	echo "Done."
 	echo "Check the kernel ring buffer to see the summary."
 }
@@ -74,7 +98,8 @@ run_smoke_check()
 	echo "Please check $0 output how it can be used"
 	echo "for deep performance analysis as well as stress testing."
 
-	modprobe $DRIVER $SMOKE_PARAM > /dev/null 2>&1
+	check_memory_requirement
+	modprobe $DRIVER $SMOKE_PARAM $PCPU_OBJ_PARAM > /dev/null 2>&1
 	echo "Done."
 	echo "Check the kernel ring buffer to see the summary."
 }