scallywag / cygport not pulling lzip

[Achim Gratz]

Brian Inglis writes:
>> Yeah, perhaps lzip should be a dependency of cygport.

Since it promises to enable it's use, yes.  I wouldn't mind to add a
dependency to tar also.

> ...and zstd as Achim is working on that.

That dependency has already been added to tar, so there is no need to do
anything special.

[as you could hav seen by looking at any of the recent CI logs]

> I do not think we should encourage use of lower compression ratio
> packages in cygport and calm, and their libraries in setup.
> It appears zstd gives up compression to gain faster decompression with
> less memory which may be advantageous for loading a kernel, but less
> optimal for MBs of base packages.

That difference is in the order of 3% over the full distribution at the
highest compression setting and roughly 5% is you use a compression
setting that is about as slow as xz.  The installation time on the other
hand is dramatically shorter with zstd.

> Perhaps consideration should also be given to setting appropriate
> compression defaults in cygport for all supported package compressors
> e.g. GZIP=-9, XZ_OPT=-7 which does not increase the memory required
> from the default -6 but improves compression, ZSTD_CLEVEL=19 and
> ZSTD_NBTHREADS=`nproc` perhaps?

It is relatively useless to have zstd run with multiple threads in
compression mode since a lot of what takes time there is inherently
single threaded.  It already does use an I/O thread to keep the data
pipes fed unless you specifically forbid that.


Regards,
Achim.
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