[systemd-devel] [PATCH 2/2] compress: add benchmark-style test

[Kay Sievers]

On Mon, Jul 7, 2014 at 10:33 PM, Zbigniew Jędrzejewski-Szmek
<zbyszek at in.waw.pl> wrote:
> On Mon, Jul 07, 2014 at 09:47:15PM +0200, Kay Sievers wrote:
>> On Mon, Jul 7, 2014 at 9:40 PM, Zbigniew Jędrzejewski-Szmek
>> <zbyszek at in.waw.pl> wrote:
>> > On Mon, Jul 07, 2014 at 09:35:06PM +0300, Uoti Urpala wrote:
>> >> On Sat, 2014-07-05 at 20:56 +0200, Zbigniew Jędrzejewski-Szmek wrote:
>> >> > This is useful to test the behaviour of the compressor for various buffer
>> >> > sizes.
>> >> >
>> >> > Time is limited to a minute per compression, since otherwise, when LZ4
>> >> > takes more than a second which is necessary to reduce the noise, XZ
>> >> > takes more than 10 minutes.
>> >> >
>> >> > % build/test-compress-benchmark (without time limit)
>> >> > XZ: compressed & decompressed 2535300963 bytes in 794.57s (3.04MiB/s), mean compresion 99.95%, skipped 3570 bytes
>> >> > LZ4: compressed & decompressed 2535303543 bytes in 1.56s (1550.07MiB/s), mean compresion 99.60%, skipped 990 bytes
>> >>
>> >> Like your earlier comparison, this compares the wrong thing. If
>> >> compression speed matters more than best compression ratio, you
>> >> shouldn't use the default settings for xz. If you want to compare with
>> >> LZ4, this benchmark should at least compare the equivalent of "xz -0".
>>
>> > The comparison should be done for whatever setting is used in journald
>> > and/or coredump.
>>
>> No, The current defaults are irrelevant.
>>
>> The comparison should be done with values that indicate that
>> introducing a new compression algorithm is needed. If xz *can* be
>> instructed to reach acceptable results, we would better stick with it.
> With preset=default (6):
> XZ: compressed & decompressed 220536103 bytes in 60.03s (3.50MiB/s), ...
>
> With 0:
> XZ: compressed & decompressed 2535300963 bytes in 33.01s (73.25MiB/s), ...
>
> LZ4: compressed & decompressed 2535303543 bytes in 1.31s (1838.75MiB/s), ...

Interesting numbers. Thanks for providing them.

Kay