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Re: [PATCH v5 4/5] qcow2: add zstd cluster compression

From: Vladimir Sementsov-Ogievskiy
Subject: Re: [PATCH v5 4/5] qcow2: add zstd cluster compression
Date: Thu, 5 Mar 2020 12:56:40 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1

04.03.2020 16:35, Denis Plotnikov wrote:
zstd significantly reduces cluster compression time.
It provides better compression performance maintaining
the same level of the compression ratio in comparison with
zlib, which, at the moment, is the only compression
method available.

The performance test results:
Test compresses and decompresses qemu qcow2 image with just
installed rhel-7.6 guest.
Image cluster size: 64K. Image on disk size: 2.2G

The test was conducted with brd disk to reduce the influence
of disk subsystem to the test results.
The results is given in seconds.

compress cmd:
   time ./qemu-img convert -O qcow2 -c -o compression_type=[zlib|zstd]
                   src.img [zlib|zstd]_compressed.img
decompress cmd
   time ./qemu-img convert -O qcow2
                   [zlib|zstd]_compressed.img uncompressed.img

            compression               decompression
          zlib       zstd           zlib         zstd
real     65.5       16.3 (-75 %)    1.9          1.6 (-16 %)
user     65.0       15.8            5.3          2.5
sys       3.3        0.2            2.0          2.0

Both ZLIB and ZSTD gave the same compression ratio: 1.57
compressed image size in both cases: 1.4G

Signed-off-by: Denis Plotnikov <address@hidden>
QAPI part:
Acked-by: Markus Armbruster <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>

Looks a bit like I've reviewed only QAPI part, when actually my r-b is for full 

May be

Acked-by: Markus Armbruster <address@hidden>
          [QAPI part]
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>

Best regards,

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