[PATCH v2 5/6] lnst.Recipes.ENRT.PerfTestMixins: add DropCachesPerfTestMixin

[Jan Tluka]

This mixin class can be used to drop vm caches before each iteration
of the performance test measurements.

v2:

The mixin will drop caches on all machines that were matched by recipe
instead of just the generator and receiver machines. This is desired
for the scenarios with virtual guests.

Signed-off-by: Jan Tluka <jtluka(a)redhat.com&gt;
---
 .../PerfTestMixins/DropCachesPerfTestMixin.py | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 lnst/Recipes/ENRT/PerfTestMixins/DropCachesPerfTestMixin.py

diff --git a/lnst/Recipes/ENRT/PerfTestMixins/DropCachesPerfTestMixin.py
b/lnst/Recipes/ENRT/PerfTestMixins/DropCachesPerfTestMixin.py
new file mode 100644
index 00000000..36b946e7
--- /dev/null
+++ b/lnst/Recipes/ENRT/PerfTestMixins/DropCachesPerfTestMixin.py
@@ -0,0 +1,39 @@
+from lnst.Common.Parameters import BoolParam
+from lnst.RecipeCommon.Perf.PerfTestMixins import BasePerfTestIterationTweakMixin
+
+
+class DropCachesPerfTestMixin(BasePerfTestIterationTweakMixin):
+    """
+    This mixin class is an extension to the :any:`BaseEnrtRecipe` class that can
+    be used to drop vm caches before running each iteration of the performance
+    measurements.
+
+    :param drop_caches:
+        (optional test parameter) a boolean, if set to True, the memory caches
+        are dropped otherwise the mixin has no effect
+    """
+
+    drop_caches = BoolParam(default=False)
+
+    def generate_perf_test_iteration_tweak_description(self, perf_config):
+        description = super().generate_perf_test_iteration_tweak_description(
+            perf_config
+        )
+        if self.params.drop_caches:
+            for host in self.matched:
+                description.append(
+                    "dropped vm caches before iteration on host
{}".format(host.hostid)
+                )
+        else:
+            description.append("skipped dropping vm caches before iteration")
+        return description
+
+    def apply_perf_test_iteration_tweak(self, perf_config):
+        super().apply_perf_test_iteration_tweak(perf_config)
+
+        if self.params.drop_caches:
+            for host in self.matched:
+                host.run("echo 1 > /proc/sys/vm/drop_caches")
+
+    def remove_perf_test_iteration_tweak(self, perf_config):
+        super().remove_perf_test_iteration_tweak(perf_config)
-- 
2.21.3