testscript: do huge-page tests first to prevent memory fragmentation

The more test cases we have, the more allocations will happen in the VM
hosts (the QEMU VMs). This causes memory fragmentation. We have more and
more frequent CI failures with the huge page tests. Our assumption is that
the memory is too fragmented to allocate 2 GiB of huge pages
(1024x 2 MiB pages). By executing the huge-page tests first, we can
work around this.

On-behalf-of: SAP philipp.schuster@sap.com
Signed-off-by: Philipp Schuster <philipp.schuster@cyberus-technology.de>

Author: phip1611

tests/testscript.py

@@ -19,7 +19,7 @@
 VIRTIO_ENTROPY_SOURCE = "1af4:1044"
 
 # The VM we migrate has 2GiB of memory: 1024 * 2 MiB to cover RAM
-nr_hugepages = 1024
+NR_HUGEPAGES = 1024
 
 
 class SaveLogsOnErrorTestCase(unittest.TestCase):
@@ -590,17 +590,17 @@ def test_live_migration_with_hugepages(self):
         Test that a VM that utilizes hugepages is still using hugepages after live migration.
         """
 
-        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(nr_hugepages))
-        computeVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(nr_hugepages))
+        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(NR_HUGEPAGES))
+        computeVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(NR_HUGEPAGES))
         status, out = controllerVM.execute(
             "awk '/HugePages_Free/ { print $2; exit }' /proc/meminfo"
         )
-        assert int(out) == nr_hugepages, "unable to allocate hugepages"
+        assert int(out) == NR_HUGEPAGES, "unable to allocate hugepages"
 
         status, out = computeVM.execute(
             "awk '/HugePages_Free/ { print $2; exit }' /proc/meminfo"
         )
-        assert int(out) == nr_hugepages, "unable to allocate hugepages"
+        assert int(out) == NR_HUGEPAGES, "unable to allocate hugepages"
 
         controllerVM.succeed("virsh define /etc/domain-chv-hugepages-prefault.xml")
         controllerVM.succeed("virsh start testvm")
@@ -626,18 +626,18 @@ def test_live_migration_with_hugepages(self):
         status, out = controllerVM.execute(
             "awk '/HugePages_Free/ { print $2; exit }' /proc/meminfo"
         )
-        assert int(out) == nr_hugepages, "not all huge pages have been freed"
+        assert int(out) == NR_HUGEPAGES, "not all huge pages have been freed"
 
     def test_live_migration_with_hugepages_failure_case(self):
         """
         Test that migrating a VM with hugepages to a destination without huge pages will fail gracefully.
         """
 
-        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(nr_hugepages))
+        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(NR_HUGEPAGES))
         status, out = controllerVM.execute(
             "awk '/HugePages_Free/ { print $2; exit }' /proc/meminfo"
         )
-        assert int(out) == nr_hugepages, "unable to allocate hugepages"
+        assert int(out) == NR_HUGEPAGES, "unable to allocate hugepages"
 
         controllerVM.succeed("virsh define /etc/domain-chv-hugepages-prefault.xml")
         controllerVM.succeed("virsh start testvm")
@@ -692,7 +692,7 @@ def test_hugepages(self):
         Test hugepage on-demand usage for a non-NUMA VM.
         """
 
-        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(nr_hugepages))
+        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(NR_HUGEPAGES))
         controllerVM.succeed("virsh define /etc/domain-chv-hugepages.xml")
         controllerVM.succeed("virsh start testvm")
 
@@ -702,16 +702,14 @@ def test_hugepages(self):
         status, out = controllerVM.execute(
             "awk '/HugePages_Free/ { print $2; exit }' /proc/meminfo"
         )
-        assert int(out) < nr_hugepages, "No huge pages have been used"
+        assert int(out) < NR_HUGEPAGES, "No huge pages have been used"
 
     def test_hugepages_prefault(self):
         """
         Test hugepage usage with pre-faulting for a non-NUMA VM.
         """
 
-        nr_hugepages = 1024
-
-        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(nr_hugepages))
+        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(NR_HUGEPAGES))
         controllerVM.succeed("virsh define /etc/domain-chv-hugepages-prefault.xml")
         controllerVM.succeed("virsh start testvm")
 
@@ -728,7 +726,7 @@ def test_numa_hugepages(self):
         Test hugepage on-demand usage for a NUMA VM.
         """
 
-        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(nr_hugepages))
+        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(NR_HUGEPAGES))
         controllerVM.succeed("virsh define /etc/domain-chv-numa-hugepages.xml")
         controllerVM.succeed("virsh start testvm")
 
@@ -745,14 +743,14 @@ def test_numa_hugepages(self):
         status, out = controllerVM.execute(
             "awk '/HugePages_Free/ { print $2; exit }' /proc/meminfo"
         )
-        assert int(out) < nr_hugepages, "No huge pages have been used"
+        assert int(out) < NR_HUGEPAGES, "No huge pages have been used"
 
     def test_numa_hugepages_prefault(self):
         """
         Test hugepage usage with pre-faulting for a NUMA VM.
         """
 
-        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(nr_hugepages))
+        controllerVM.succeed("echo {} > /proc/sys/vm/nr_hugepages".format(NR_HUGEPAGES))
         controllerVM.succeed("virsh define /etc/domain-chv-numa-hugepages-prefault.xml")
         controllerVM.succeed("virsh start testvm")
 
@@ -1882,6 +1880,15 @@ def test_bdf_valid_device_id_with_function_id(self):
 def suite():
     # Test cases in alphabetical order
     testcases = [
+        # First everything with huge-pages to prevent memory-fragmentation
+        # preventing huge-page allocation
+        LibvirtTests.test_numa_hugepages,
+        LibvirtTests.test_numa_hugepages_prefault,
+        LibvirtTests.test_hugepages,
+        LibvirtTests.test_hugepages_prefault,
+        LibvirtTests.test_live_migration_with_hugepages,
+        LibvirtTests.test_live_migration_with_hugepages_failure_case,
+        # Next, all other test cases.
         LibvirtTests.test_bdf_explicit_assignment,
         LibvirtTests.test_bdf_implicit_assignment,
         LibvirtTests.test_bdf_invalid_device_id,
@@ -1892,8 +1899,6 @@ def suite():
         LibvirtTests.test_disk_resize_qcow2,
         LibvirtTests.test_disk_resize_raw,
         LibvirtTests.test_hotplug,
-        LibvirtTests.test_hugepages,
-        LibvirtTests.test_hugepages_prefault,
         LibvirtTests.test_libvirt_event_stop_failed,
         LibvirtTests.test_libvirt_restart,
         LibvirtTests.test_live_migration,
@@ -1905,8 +1910,6 @@ def suite():
         LibvirtTests.test_live_migration_virsh_non_blocking,
         LibvirtTests.test_live_migration_with_hotplug,
         LibvirtTests.test_live_migration_with_hotplug_and_virtchd_restart,
-        LibvirtTests.test_live_migration_with_hugepages,
-        LibvirtTests.test_live_migration_with_hugepages_failure_case,
         LibvirtTests.test_live_migration_with_serial_tcp,
         LibvirtTests.test_live_migration_with_vcpu_pinning,
         LibvirtTests.test_managedsave,
@@ -1915,8 +1918,6 @@ def suite():
         LibvirtTests.test_network_hotplug_persistent_transient_detach_vm_restart,
         LibvirtTests.test_network_hotplug_persistent_vm_restart,
         LibvirtTests.test_network_hotplug_transient_vm_restart,
-        LibvirtTests.test_numa_hugepages,
-        LibvirtTests.test_numa_hugepages_prefault,
         LibvirtTests.test_numa_topology,
         LibvirtTests.test_serial_file_output,
         LibvirtTests.test_serial_tcp,