[PATCH v2] selftests/vm/run_vmtests: adjust hugetlb size accroding to nr_cpus

[Li Zhijian]

Fix userfaultfd_hugetlb on hosts which have more than 64 cpus.

---------------------------
running userfaultfd_hugetlb
---------------------------
invalid MiB
Usage: <MiB> <bounces>
[FAIL]

Via userfaultfd.c we can know, hugetlb_size needs to meet hugetlb_size >=
nr_cpus * hugepage_size.  hugepage_size is often 2M, so when host cpus >
64, it requires more than 128M.

Changes since v1:
  - update changelog/comments and variable name to make code more easier to
    read/understand(stolen from Mike Kravetz)

Link: http://lkml.kernel.org/r/20180302024356.83359-1-zhijianx.li@xxxxxxxxx
Signed-off-by: Li Zhijian <zhijianx.li@xxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: SeongJae Park <sj38.park@xxxxxxxxx>
Cc: Philippe Ombredanne <pombredanne@xxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 tools/testing/selftests/vm/run_vmtests | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests
index d2561895a021a..22d5646738302 100755
--- a/tools/testing/selftests/vm/run_vmtests
+++ b/tools/testing/selftests/vm/run_vmtests
@@ -2,25 +2,33 @@
 # SPDX-License-Identifier: GPL-2.0
 #please run as root
 
-#we need 256M, below is the size in kB
-needmem=262144
 mnt=./huge
 exitcode=0
 
-#get pagesize and freepages from /proc/meminfo
+#get huge pagesize and freepages from /proc/meminfo
 while read name size unit; do
 	if [ "$name" = "HugePages_Free:" ]; then
 		freepgs=$size
 	fi
 	if [ "$name" = "Hugepagesize:" ]; then
-		pgsize=$size
+		hpgsize_KB=$size
 	fi
 done < /proc/meminfo
 
+# Simple hugetlbfs tests have a hardcoded minimum requirement of
+# huge pages totaling 256MB (262144KB) in size.  The userfaultfd
+# hugetlb test requires a minimum of 2 * nr_cpus huge pages.  Take
+# both of these requirements into account and attempt to increase
+# number of huge pages available.
+nr_cpus=$(nproc)
+hpgsize_MB=$((hpgsize_KB / 1024))
+half_ufd_size_MB=$((((nr_cpus * hpgsize_MB + 127) / 128) * 128))
+needmem_KB=$((half_ufd_size_MB * 2 * 1024))
+
 #set proper nr_hugepages
-if [ -n "$freepgs" ] && [ -n "$pgsize" ]; then
+if [ -n "$freepgs" ] && [ -n "$hpgsize_KB" ]; then
 	nr_hugepgs=`cat /proc/sys/vm/nr_hugepages`
-	needpgs=`expr $needmem / $pgsize`
+	needpgs=$((needmem_KB / hpgsize_KB))
 	tries=2
 	while [ $tries -gt 0 ] && [ $freepgs -lt $needpgs ]; do
 		lackpgs=$(( $needpgs - $freepgs ))
@@ -107,8 +115,9 @@ fi
 echo "---------------------------"
 echo "running userfaultfd_hugetlb"
 echo "---------------------------"
-# 256MB total huge pages == 128MB src and 128MB dst
-./userfaultfd hugetlb 128 32 $mnt/ufd_test_file
+# Test requires source and destination huge pages.  Size of source
+# (half_ufd_size_MB) is passed as argument to test.
+./userfaultfd hugetlb $half_ufd_size_MB 32 $mnt/ufd_test_file
 if [ $? -ne 0 ]; then
 	echo "[FAIL]"
 	exitcode=1
-- 
2.11.0