examples: add osv-memusage

this ukbench script measures the peak RSS of an OSv unikernel for
Firecracker and QEMU (helloworld).

Signed-off-by: Hugo Lefeuvre <hugo.lefeuvre@manchester.ac.uk>

examples/osv-memusage/osv-memusage.patch

@@ -0,0 +1,26 @@
+diff --git a/scripts/firecracker.py b/scripts/firecracker.py
+index d0b24071..b26f6cd7 100755
+--- a/scripts/firecracker.py
++++ b/scripts/firecracker.py
+@@ -237,7 +237,7 @@ def start_firecracker_with_no_api(firecracker_path, firecracker_config_json):
+     api_file.write(bytes(firecracker_config_json, 'utf-8'))
+     api_file.flush()
+     stty_save()
+-    return subprocess.Popen([firecracker_path, "--no-api", "--config-file", api_file.name],
++    return subprocess.Popen(['/usr/bin/time', '-f', 'Firecracker maxRSS: %M', firecracker_path, "--no-api", "--config-file", api_file.name],
+                            stdout=sys.stdout, stderr=subprocess.STDOUT), api_file.name
+
+
+diff --git a/scripts/run.py b/scripts/run.py
+index c7464bda..d9cdbeaf 100755
+--- a/scripts/run.py
++++ b/scripts/run.py
+@@ -272,7 +272,7 @@ def start_osv_qemu(options):
+
+         qemu_env['OSV_BRIDGE'] = options.bridge
+         qemu_path = options.qemu_path or ('qemu-system-%s' % options.arch)
+-        cmdline = [qemu_path] + args
++        cmdline = ['/usr/bin/time', '-f', 'QEMU maxRSS: %M', qemu_path] + args
+         if options.dry_run:
+             print(format_args(cmdline))
+         else:

examples/osv-memusage/osv-memusage.yaml

@@ -0,0 +1,46 @@
+params:
+  - name: TEST
+    type: string
+    only: ["Hello"]
+
+inputs:
+  - source: osv-memusage.patch
+    destination: /root/osv-memusage.patch
+  - source: /etc/resolv.conf
+    destination: /etc/resolv.conf
+  - source: /etc/environment
+    destination: /etc/environment
+
+outputs:
+  - path: /results.txt
+
+runs:
+  - name: run
+    image: hlefeuvre/osv
+    cores: 1
+    devices:
+      - /dev/kvm
+      - /dev/net/tun
+    capabilities:
+      - CAP_NET_ADMIN
+    cmd:
+      |
+      set -xe
+      for env in $( cat /etc/environment ); do \
+        export $(echo $env | sed -e 's/"//g'); \
+      done
+
+      env
+
+      touch /results.txt
+
+      apt update && apt install -y time
+
+      cd  /root/osv/
+      git apply --ignore-space-change /root/osv-memusage.patch
+
+      script -c '/root/osv/scripts/run.py' -f /tmp/out
+      cat /tmp/out | grep "QEMU maxRSS: " >> /results.txt
+
+      script -c '/root/osv/scripts/firecracker.py' -f /tmp/out
+      cat /tmp/out | grep "Firecracker maxRSS: " >> /results.txt