qemu-iotests: Test I/O in a single drive from a throttling group

iotest 093 contains a test that creates a throttling group with
several drives and performs I/O in all of them. This patch adds a new
test that creates a similar setup but only performs I/O in one of the
drives at the same time.

This is useful to test that the round robin algorithm is behaving
properly in these scenarios, and is specifically written using the
regression introduced in 27ccdd5 as an example.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit a26ddb4)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

tests/qemu-iotests/093

@@ -53,7 +53,7 @@ class ThrottleTestCase(iotests.QMPTestCase):
             result = self.vm.qmp("block_set_io_throttle", conv_keys=False, **params)
             self.assert_qmp(result, 'return', {})
 
-    def do_test_throttle(self, ndrives, seconds, params):
+    def do_test_throttle(self, ndrives, seconds, params, first_drive = 0):
         def check_limit(limit, num):
             # IO throttling algorithm is discrete, allow 10% error so the test
             # is more robust
@@ -85,12 +85,14 @@ class ThrottleTestCase(iotests.QMPTestCase):
         # 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" %
+                idx = first_drive + drive
+                self.vm.hmp_qemu_io("drive%d" % idx, "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" %
+                idx = first_drive + drive
+                self.vm.hmp_qemu_io("drive%d" % idx, "aio_write %d %d" %
                                     (i * rq_size, rq_size))
 
         # We'll store the I/O stats for each drive in these arrays
@@ -105,15 +107,17 @@ class ThrottleTestCase(iotests.QMPTestCase):
 
         # Read the stats before advancing the clock
         for i in range(0, ndrives):
+            idx = first_drive + i
             start_rd_bytes[i], start_rd_iops[i], start_wr_bytes[i], \
-                start_wr_iops[i] = self.blockstats('drive%d' % i)
+                start_wr_iops[i] = self.blockstats('drive%d' % idx)
 
         self.vm.qtest("clock_step %d" % ns)
 
         # Read the stats after advancing the clock
         for i in range(0, ndrives):
+            idx = first_drive + i
             end_rd_bytes[i], end_rd_iops[i], end_wr_bytes[i], \
-                end_wr_iops[i] = self.blockstats('drive%d' % i)
+                end_wr_iops[i] = self.blockstats('drive%d' % idx)
 
         # Check that the I/O is within the limits and evenly distributed
         for i in range(0, ndrives):
@@ -129,6 +133,7 @@ class ThrottleTestCase(iotests.QMPTestCase):
             self.assertTrue(check_limit(params['iops_rd'], rd_iops))
             self.assertTrue(check_limit(params['iops_wr'], wr_iops))
 
+    # Connect N drives to a VM and test I/O in all of them
     def test_all(self):
         params = {"bps": 4096,
                   "bps_rd": 4096,
@@ -146,6 +151,24 @@ class ThrottleTestCase(iotests.QMPTestCase):
                 self.configure_throttle(ndrives, limits)
                 self.do_test_throttle(ndrives, 5, limits)
 
+    # Connect N drives to a VM and test I/O in just one of them a time
+    def test_one(self):
+        params = {"bps": 4096,
+                  "bps_rd": 4096,
+                  "bps_wr": 4096,
+                  "iops": 10,
+                  "iops_rd": 10,
+                  "iops_wr": 10,
+                 }
+        # Repeat the test for each one of the drives
+        for drive in range(0, self.max_drives):
+            # 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] * self.max_drives
+                self.configure_throttle(self.max_drives, limits)
+                self.do_test_throttle(1, 5, limits, drive)
+
     def test_burst(self):
         params = {"bps": 4096,
                   "bps_rd": 4096,

tests/qemu-iotests/093.out

@@ -1,5 +1,5 @@
-.....
+.......
 ----------------------------------------------------------------------
-Ran 5 tests
+Ran 7 tests
 
 OK