On 11/10/2015 01:01 PM, David Rientjes wrote: > On Sat, 31 Oct 2015, Ben Hutchings wrote: > >> If we need to increase the number of huge pages, drop caches first >> to reduce fragmentation and then check that we actually allocated >> as many as we wanted. Retry once if that doesn't work. >> >> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> >> --- >> The test always fails for me in a 1 GB VM without this. >> >> Ben. >> >> tools/testing/selftests/vm/run_vmtests | 15 ++++++++++++++- >> 1 file changed, 14 insertions(+), 1 deletion(-) >> >> diff --git a/tools/testing/selftests/vm/run_vmtests b/tools/testing/selftests/vm/run_vmtests >> index 9179ce8..97ed1b2 100755 >> --- a/tools/testing/selftests/vm/run_vmtests >> +++ b/tools/testing/selftests/vm/run_vmtests >> @@ -20,13 +20,26 @@ done < /proc/meminfo >> if [ -n "$freepgs" ] && [ -n "$pgsize" ]; then >> nr_hugepgs=`cat /proc/sys/vm/nr_hugepages` >> needpgs=`expr $needmem / $pgsize` >> - if [ $freepgs -lt $needpgs ]; then >> + tries=2 >> + while [ $tries -gt 0 ] && [ $freepgs -lt $needpgs ]; do >> lackpgs=$(( $needpgs - $freepgs )) >> + echo 3 > /proc/sys/vm/drop_caches >> echo $(( $lackpgs + $nr_hugepgs )) > /proc/sys/vm/nr_hugepages >> if [ $? -ne 0 ]; then >> echo "Please run this test as root" >> exit 1 >> fi >> + while read name size unit; do >> + if [ "$name" = "HugePages_Free:" ]; then >> + freepgs=$size >> + fi >> + done < /proc/meminfo >> + tries=$((tries - 1)) >> + done >> + if [ $freepgs -lt $needpgs ]; then >> + printf "Not enough huge pages available (%d < %d)\n" \ >> + $freepgs $needpgs >> + exit 1 >> fi >> else >> echo "no hugetlbfs support in kernel?" >> > > I know this patch is in -mm and hasn't been merged by Linus yet, but I'm > wondering why the multiple /proc/sys/vm/drop_caches is helping? Would it > simply suffice to put a sleep in there instead or is drop_caches actually > doing something useful a second time around? > I sent this up for merge in my pull request. Adding sleep would increase test run-time. Something to keep in mind. thanks, -- Shuah -- Shuah Khan Sr. Linux Kernel Developer Open Source Innovation Group Samsung Research America (Silicon Valley) shuahkh@xxxxxxxxxxxxxxx | (970) 217-8978 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>