[PATCH] src-release.sh: Use -T0 for xz compression

[Sam James]

"Richard Earnshaw (lists)" <Richard.Earnshaw@arm.com> writes:

> On 31/05/2024 10:47, Mark Wielaard wrote:
>> Hi Simon,
>> 
>> On Fri, May 31, 2024 at 11:04:32AM +0900, Simon Richter wrote:
>>> On 5/31/24 06:43, Mark Wielaard wrote:
>>>
>>>> On my machine (using 4 cores) this reduces the time to create
>>>> binutils-2.42.50.tar.xz from 1 minute 40 seconds to 56 seconds.
>>>
>>> Is the output still deterministic from the input?
>> 
>> Yes, as long as one uses mult-threaded mode -T0, it doesn't matter how
>> many cores are used. It does differ from the output of serial mode
>> though, when no -T is used.
>> 
>> Cheers,
>> 
>> Mark
>
> Perhaps more importantly, for reproducibility, does it produce
> different output if run on a machine with a different number of
> available CPUs?  That might matter if you're validating the checksums
> against a version generated by somebody else from supposedly the same
> sources.

No, fortunately, the threaded compressor output is deterministic
irrespective of the hardware it is run on.

That is, xz has two output modes here:
1) the non-threaded compressor, which doesn't chunk into blocks;
2) the threaded compressor, which chunks into blocks.

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