qemu-iotests: expand test 093 to support group throttling

This patch improves the test by attaching a different number of drives
to the VM and putting them in the same throttling group. The test
verifies that the I/O is evenly distributed among all members of the
group, and that the limits are enforced.

By default the test is repeated 3 times with 1, 2 and 3 drives, but
the maximum number of simultaneous drives is configurable.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 513df1da5c658878191b579ebcddd985adcd4122.1433779731.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

tests/qemu-iotests/093

@@ -3,6 +3,7 @@
 # Tests for IO throttling
 #
 # Copyright (C) 2015 Red Hat, Inc.
+# Copyright (C) 2015 Igalia, S.L.
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -22,6 +23,7 @@ import iotests
 
 class ThrottleTestCase(iotests.QMPTestCase):
     test_img = "null-aio://"
+    max_drives = 3
 
     def blockstats(self, device):
         result = self.vm.qmp("query-blockstats")
@@ -32,24 +34,29 @@ class ThrottleTestCase(iotests.QMPTestCase):
         raise Exception("Device not found for blockstats: %s" % device)
 
     def setUp(self):
-        self.vm = iotests.VM().add_drive(self.test_img)
+        self.vm = iotests.VM()
+        for i in range(0, self.max_drives):
+            self.vm.add_drive(self.test_img)
         self.vm.launch()
 
     def tearDown(self):
         self.vm.shutdown()
 
-    def do_test_throttle(self, seconds, params):
+    def do_test_throttle(self, ndrives, seconds, params):
         def check_limit(limit, num):
             # IO throttling algorithm is discrete, allow 10% error so the test
             # is more robust
             return limit == 0 or \
-                   (num < seconds * limit * 1.1
+                   (num < seconds * limit * 1.1 / ndrives
-                   and num > seconds * limit * 0.9)
+                   and num > seconds * limit * 0.9 / ndrives)
 
         nsec_per_sec = 1000000000
 
-        params['device'] = 'drive0'
+        params['group'] = 'test'
 
+        # Set the I/O throttling parameters to all drives
+        for i in range(0, ndrives):
+            params['device'] = 'drive%d' % i
             result = self.vm.qmp("block_set_io_throttle", conv_keys=False, **params)
             self.assert_qmp(result, 'return', {})
 
@@ -66,25 +73,53 @@ class ThrottleTestCase(iotests.QMPTestCase):
                     params['iops'] / 2,
                     params['iops_rd'])
         rd_nr *= seconds * 2
+        rd_nr /= ndrives
         wr_nr = max(params['bps'] / rq_size / 2,
                     params['bps_wr'] / rq_size,
                     params['iops'] / 2,
                     params['iops_wr'])
         wr_nr *= seconds * 2
-        for i in range(rd_nr):
+        wr_nr /= ndrives
-            self.vm.hmp_qemu_io("drive0", "aio_read %d %d" % (i * rq_size, rq_size))
-        for i in range(wr_nr):
-            self.vm.hmp_qemu_io("drive0", "aio_write %d %d" % (i * rq_size, rq_size))
 
-        start_rd_bytes, start_rd_iops, start_wr_bytes, start_wr_iops = self.blockstats('drive0')
+        # Send I/O requests to all drives
+        for i in range(rd_nr):
+            for drive in range(0, ndrives):
+                self.vm.hmp_qemu_io("drive%d" % drive, "aio_read %d %d" %
+                                    (i * rq_size, rq_size))
+
+        for i in range(wr_nr):
+            for drive in range(0, ndrives):
+                self.vm.hmp_qemu_io("drive%d" % drive, "aio_write %d %d" %
+                                    (i * rq_size, rq_size))
+
+        # We'll store the I/O stats for each drive in these arrays
+        start_rd_bytes = [0] * ndrives
+        start_rd_iops  = [0] * ndrives
+        start_wr_bytes = [0] * ndrives
+        start_wr_iops  = [0] * ndrives
+        end_rd_bytes   = [0] * ndrives
+        end_rd_iops    = [0] * ndrives
+        end_wr_bytes   = [0] * ndrives
+        end_wr_iops    = [0] * ndrives
+
+        # Read the stats before advancing the clock
+        for i in range(0, ndrives):
+            start_rd_bytes[i], start_rd_iops[i], start_wr_bytes[i], \
+                start_wr_iops[i] = self.blockstats('drive%d' % i)
 
         self.vm.qtest("clock_step %d" % ns)
-        end_rd_bytes, end_rd_iops, end_wr_bytes, end_wr_iops = self.blockstats('drive0')
 
-        rd_bytes = end_rd_bytes - start_rd_bytes
+        # Read the stats after advancing the clock
-        rd_iops = end_rd_iops - start_rd_iops
+        for i in range(0, ndrives):
-        wr_bytes = end_wr_bytes - start_wr_bytes
+            end_rd_bytes[i], end_rd_iops[i], end_wr_bytes[i], \
-        wr_iops = end_wr_iops - start_wr_iops
+                end_wr_iops[i] = self.blockstats('drive%d' % i)
+
+        # Check that the I/O is within the limits and evenly distributed
+        for i in range(0, ndrives):
+            rd_bytes = end_rd_bytes[i] - start_rd_bytes[i]
+            rd_iops = end_rd_iops[i] - start_rd_iops[i]
+            wr_bytes = end_wr_bytes[i] - start_wr_bytes[i]
+            wr_iops = end_wr_iops[i] - start_wr_iops[i]
 
             self.assertTrue(check_limit(params['bps'], rd_bytes + wr_bytes))
             self.assertTrue(check_limit(params['bps_rd'], rd_bytes))
@@ -101,11 +136,13 @@ class ThrottleTestCase(iotests.QMPTestCase):
                   "iops_rd": 10,
                   "iops_wr": 10,
                  }
+        # Repeat the test with different numbers of drives
+        for ndrives in range(1, self.max_drives + 1):
             # Pick each out of all possible params and test
             for tk in params:
                 limits = dict([(k, 0) for k in params])
-            limits[tk] = params[tk]
+                limits[tk] = params[tk] * ndrives
-            self.do_test_throttle(5, limits)
+                self.do_test_throttle(ndrives, 5, limits)
 
 class ThrottleTestCoroutine(ThrottleTestCase):
     test_img = "null-co://"