perf-test: Permit 100% overcommit

It's ok to use all the memory, we aren't running other workloads while
benchmarking.

Author: tautschnig

scripts/perf-test/run-on-ec2.sh

@@ -25,6 +25,9 @@ chmod o+wt '/sys/fs/cgroup/cpu,cpuacct/user.slice'
 chmod o+wt '/sys/fs/cgroup/memory/user.slice'
 chmod o+wt '/sys/fs/cgroup/freezer/'
 
+# we can use all the memory
+echo 100 > /proc/sys/vm/overcommit_ratio
+
 # update benchmarks
 cd /mnt/sv-benchmarks
 git pull