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

[Markus Armbruster <armbru@redhat.com>]

Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> writes:

> 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 <dplotnikov@virtuozzo.com>
>> QAPI part:
>> Acked-by: Markus Armbruster <armbru@redhat.com>
>> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
>
> Looks a bit like I've reviewed only QAPI part, when actually my r-b is for full patch...
>
> May be
>
> Acked-by: Markus Armbruster <armbru@redhat.com>
>           [QAPI part]
> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

No objection.

We habitually use

  Acked-by: Markus Armbruster <armbru@redhat.com>
  Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

I'm okay with that, too.