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

[Peter Korsgaard <peter@korsgaard.com>]

>>>>> "Thomas" == Thomas Petazzoni <thomas.petazzoni@bootlin.com> writes:

 > Hello,
 > On Mon, 21 Jan 2019 18:39:24 +0100, Peter Korsgaard wrote:

 >> > I thought it was using the version compiled by buildroot.
 >> > Isn't that what host-xz is being used for?  
 >> 
 >> Yes, correct. Do you know if the -T 0 option generates identical output
 >> as -T 1? Otherwise we may want to disable it for reproducible builds.

 > 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.

What I really meant was if the -T 1 option affected the output format,
and if so, if the difference involved any tradeoff (E.G. perhaps -T 1
compresses slightly worse than -T 0) and if repeated runs with -T 1
would generate the same output (on same machine or on another machine
with different number of threads).

 > 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.

-- 
Bye, Peter Korsgaard