[PATCH v5] scripts/simplebench: compare write request performance

[Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>]

The script 'bench_write_req.py' allows comparing performances of write
request for two qemu-img binary files.
An example with (qemu-img binary 1) and without (qemu-img binary 2) the
applied patch "qcow2: skip writing zero buffers to empty COW areas"
(git commit ID: c8bb23cbdbe32f5) has the following results:

SSD:
----------------  -------------------  -------------------
                  <qemu-img binary 1>  <qemu-img binary 2>
<cluster front>   0.10 +- 0.00         8.16 +- 0.65
<cluster middle>  0.10 +- 0.00         7.37 +- 1.10
<cross cluster>   7.40 +- 1.08         21.97 +- 4.19
<cluster 64K>     2.14 +- 0.94         8.48 +- 1.66
----------------  -------------------  -------------------
HDD:
----------------  -------------------  -------------------
                  <qemu-img binary 1>  <qemu-img binary 2>
<cluster front>   2.30 +- 0.01         6.19 +- 0.06
<cluster middle>  2.20 +- 0.09         6.20 +- 0.06
<cross cluster>   8.32 +- 0.16         8.26 +- 0.14
<cluster 64K>     8.20 +- 0.05         6.26 +- 0.10
----------------  -------------------  -------------------

Suggested-by: Denis V. Lunev <den@openvz.org>
Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
v5:
  01: 'cluster_size' made variable.
  02: <simple case> deleted as duplicated.
  03: A case with cluster size 64K was added.
  04: The comments amended as Vladimir suggested.
  05: Superfluous variables removed.
  06: 'finally' block removed from function bench_write_req()
  07: The names of test cases changed.
  08: The 'block_size' of <cross cluster> set to the cluster size.

 scripts/simplebench/bench_write_req.py | 170 +++++++++++++++++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100755 scripts/simplebench/bench_write_req.py

diff --git a/scripts/simplebench/bench_write_req.py b/scripts/simplebench/bench_write_req.py
new file mode 100755
index 0000000..7665c4b
--- /dev/null
+++ b/scripts/simplebench/bench_write_req.py
@@ -0,0 +1,170 @@
+#!/usr/bin/env python3
+#
+# Test to compare performance of write requests for two qemu-img binary files.
+#
+# The idea of the test comes from intention to check the benefit of c8bb23cbdbe
+# "qcow2: skip writing zero buffers to empty COW areas".
+#
+# Copyright (c) 2020 Virtuozzo International GmbH.
+#
+# 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
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+
+import sys
+import os
+import subprocess
+import simplebench
+
+
+def bench_func(env, case):
+    """ Handle one "cell" of benchmarking table. """
+    return bench_write_req(env['qemu_img'], env['image_name'],
+                           case['block_size'], case['block_offset'],
+                           case['cluster_size'])
+
+
+def qemu_img_pipe(*args):
+    '''Run qemu-img and return its output'''
+    subp = subprocess.Popen(list(args),
+                            stdout=subprocess.PIPE,
+                            stderr=subprocess.STDOUT,
+                            universal_newlines=True)
+    exitcode = subp.wait()
+    if exitcode < 0:
+        sys.stderr.write('qemu-img received signal %i: %s\n'
+                         % (-exitcode, ' '.join(list(args))))
+    return subp.communicate()[0]
+
+
+def bench_write_req(qemu_img, image_name, block_size, block_offset,
+                    cluster_size):
+    """Benchmark write requests
+
+    The function creates a QCOW2 image with the given path/name. Then it runs
+    the 'qemu-img bench' command and makes series of write requests on the
+    image clusters. Finally, it returns the total time of the write operations
+    on the disk.
+
+    qemu_img     -- path to qemu_img executable file
+    image_name   -- QCOW2 image name to create
+    block_size   -- size of a block to write to clusters
+    block_offset -- offset of the block in clusters
+    cluster_size -- size of the image cluster
+
+    Returns {'seconds': int} on success and {'error': str} on failure.
+    Return value is compatible with simplebench lib.
+    """
+
+    if not os.path.isfile(qemu_img):
+        print(f'File not found: {qemu_img}')
+        sys.exit(1)
+
+    image_dir = os.path.dirname(os.path.abspath(image_name))
+    if not os.path.isdir(image_dir):
+        print(f'Path not found: {image_name}')
+        sys.exit(1)
+
+    image_size = 1024 * 1024 * 1024
+
+    args_create = [qemu_img, 'create', '-f', 'qcow2', '-o',
+                   f'cluster_size={cluster_size}',
+                   image_name, str(image_size)]
+
+    count = int(image_size / cluster_size) - 1
+    step = str(cluster_size)
+
+    args_bench = [qemu_img, 'bench', '-w', '-n', '-t', 'none', '-c',
+                  str(count), '-s', f'{block_size}', '-o', str(block_offset),
+                  '-S', step, '-f', 'qcow2', image_name]
+
+    try:
+        qemu_img_pipe(*args_create)
+    except OSError as e:
+        os.remove(image_name)
+        return {'error': 'qemu_img create failed: ' + str(e)}
+
+    try:
+        ret = qemu_img_pipe(*args_bench)
+    except OSError as e:
+        os.remove(image_name)
+        return {'error': 'qemu_img bench failed: ' + str(e)}
+
+    os.remove(image_name)
+
+    if 'seconds' in ret:
+        ret_list = ret.split()
+        index = ret_list.index('seconds.')
+        return {'seconds': float(ret_list[index-1])}
+    else:
+        return {'error': 'qemu_img bench failed: ' + ret}
+
+
+if __name__ == '__main__':
+
+    if len(sys.argv) < 4:
+        program = os.path.basename(sys.argv[0])
+        print(f'USAGE: {program} <path to qemu-img binary file> '
+              '<path to another qemu-img to compare performance with> '
+              '<full or relative name for QCOW2 image to create>')
+        exit(1)
+
+    # Test-cases are "rows" in benchmark resulting table, 'id' is a caption
+    # for the row, other fields are handled by bench_func.
+    test_cases = [
+        {
+            'id': '<cluster front>',
+            'block_size': 4096,
+            'block_offset': 0,
+            'cluster_size': 1048576
+        },
+        {
+            'id': '<cluster middle>',
+            'block_size': 4096,
+            'block_offset': 524288,
+            'cluster_size': 1048576
+        },
+        {
+            'id': '<cross cluster>',
+            'block_size': 1048576,
+            'block_offset': 4096,
+            'cluster_size': 1048576
+        },
+        {
+            'id': '<cluster 64K>',
+            'block_size': 4096,
+            'block_offset': 0,
+            'cluster_size': 65536
+        },
+   ]
+
+    # Test-envs are "columns" in benchmark resulting table, 'id is a caption
+    # for the column, other fields are handled by bench_func.
+    # Set the paths below to desired values
+    test_envs = [
+        {
+            'id': '<qemu-img binary 1>',
+            'qemu_img': f'{sys.argv[1]}',
+            'image_name': f'{sys.argv[3]}'
+        },
+        {
+            'id': '<qemu-img binary 2>',
+            'qemu_img': f'{sys.argv[2]}',
+            'image_name': f'{sys.argv[3]}'
+        },
+    ]
+
+    result = simplebench.bench(bench_func, test_envs, test_cases, count=3,
+                               initial_run=False)
+    print(simplebench.ascii(result))
-- 
1.8.3.1