Dne 30. 05. 19 v 14:57 Kevin Kofler napsal(a):
> Jason L Tibbitts III wrote:
>
>>>>>>> "BC" == Ben Cotton <bcotton(a)redhat.com>
writes:
>> BC> * The recommended compression level is 19. The builds will take
>> BC> longer, but the additional compression time is negligible in the
>> BC> total build time and it pays off in better compression ratio than xz
>> BC> lvl2 has.
>>
>> That seems different than other results I've seen. According to the
>> wikipedia page (
https://en.wikipedia.org/wiki/Zstandard) and the
>> references therein, Ubuntu found that zstd level 19 was faster but with
>> poorer compression when compared with xz level 2 (which is the same
>> level that we use now).
I haven't recompiled all Fedora, hoping that the package set I used
(Livecd RPMs) is a good sample. Thanks for pointing this out.
>
> If the smallest size is the goal, wouldn't it be worth trying to just use a
> higher xz level instead?
That would increase the compression ratio, but I don't know the impact
on compression and decompression times and also required memory for both
operations.
On modern system with NVMEs, CPU seems to be the bottleneck and it might
get worse if we increase xz compression level.
What about constrained systems where there's limited CPU, that could
be a container or a low end cloud instance without any guarantee of
resources or a Raspberry Pi.