[Buildroot] [PATCH 1/1] fs/common.mk: enable multithreaded xz compression

[Thomas Petazzoni <thomas.petazzoni@bootlin.com>]

On Sun, 27 Jan 2019 23:06:14 +0100
Peter Korsgaard <peter@korsgaard.com> wrote:

>  > Does it matter than the output of -T 0 and -T 1 are identical ?  
> 
> It would cause an extra change in output between buildroot versions
> using -T 0 and ones using -T 1 - But OK, probably that isn't really
> important given all the other changes.

Well, BR2_REPRODUCIBLE is definitely not about guaranteeing identical
output between Buildroot versions. How could this even work, since we
are bumping the version of dozens/hundreds of packages ?

BR2_REPRODUCIBLE is about given a fixed Buildroot version and
configuration, be able to generate a binary-identical result.

>  > What matters for BR2_REPRODUCIBLE=y is if the same input, with -T 0,
>  > always provide the exact identical output.  
> 
> With the new patch that only enables -T 1 for !reproducible builds,
> that is correct.

I thought -T 0 was the problematic thing as it enabled automatic
parallelization, while -T 1 explicitly disabled parallelization.

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com