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Re: [PATCH v2] scripts/simplebench: compare write request performance

From: Andrey Shinkevich
Subject: Re: [PATCH v2] scripts/simplebench: compare write request performance
Date: Sun, 12 Jul 2020 19:07:26 +0300
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.9.0

On 11.07.2020 16:05, Vladimir Sementsov-Ogievskiy wrote:
26.06.2020 17:31, Andrey Shinkevich wrote:
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)
The <unaligned> case does not involve the COW optimization.

Good, this proves that c8bb23cbdbe32f5 makes sense.

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>
   01: Three more test cases added to the script:
       <simple case>
       <general case>

  scripts/simplebench/bench_write_req.py | 201 +++++++++++++++++++++++++++++++++
  1 file changed, 201 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..fe92d01
--- /dev/null
+++ b/scripts/simplebench/bench_write_req.py
@@ -0,0 +1,201 @@

Next, I don't understand, are you trying to fill qcow2 image by dd directly? This is strange. Even if you don't break metadata, you don't change it, so all cluster will remain empty.

I have tested and it works as designed.

This dd command doesn't hurt the metadata and fills the image with random data. The actual disk size becomes about 1G after the dd command.


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