Re: [PATCH] maintainer-scripts/gcc_release: compress xz in parallel

["Martin Liška" <mliska@suse.cz>]

On 11/9/22 03:06, Xi Ruoyao via Gcc-patches wrote:
> On Wed, 2022-11-09 at 01:52 +0000, Joseph Myers wrote:
>> On Tue, 8 Nov 2022, Xi Ruoyao via Gcc-patches wrote:
>>
>>> I'm wondering if running xz -T0 on different machines (with different
>>> core numbers) may produce different compressed data.  The difference can
>>> cause trouble distributing checksums.
>>
>> gcc_release definitely doesn't use any options to make the tar file
>> reproducible (the timestamps, user and group names and ordering of the
>> files in the tarball, and quite likely permissions other than whether a
>> file has execute permission, may depend on when the script was run and on
>> what system as what user - not just on the commit from which the tar file
>> was built).  So I don't think possible variation of xz output matters here
>> at present.
> 
> OK then.  I'm already using commands like
> 
> git archive --format=tar --prefix=gcc-$(git gcc-descr HEAD)/ HEAD | xz -T0 > ../gcc-$(git gcc-descr HEAD).tar.xz
> 
> when I generate a GCC snapshot tarball for my own use.
> 
> 

Hi.

We may consider using zstd compression that also support a multi-threaded compression
(which is stable). Note the decompression of zstd is much faster than xz.

Martin