Re: [gentoo-portage-dev] [RFC] New file layout for PKGDIR and binhosts

[Zac Medico <zmedico@gentoo.org>]

On 12/24/2014 04:01 AM, vivo75@gmail.com wrote:
> Il 24/12/2014 09:13, Zac Medico ha scritto:
>>> I like this (and it has been a long time coming).  What format are we
>>>> going to store the metadata of the use flag combinations and the rest?
>> The current approach is to store the data in an xpak segment that is
>> appended to the end of the tbz2 file. The $PKGDIR/Packages files serves
>> as a cache for the essential parts of the xpak data that are used in
>> dependency calculations.
>>
> I'd like to see the xpak data being put in it's own file at the
> _beginning_ of the tar file.
> 
> tar -Jcf \
>  ${PKGDIR}/${CATEGORY}/${PN}/${PF}-${COUNTER}.xpak \
>  tmp/${CATEGORY}:${PN}:${PF}-${COUNTER}.xpak \
>  *all_the_other_stuff*
> 
> this way reading it could be faster on some media and filesystem  and it
> would not deviate from the standard tar.

There wouldn't be any benefit, because the data is practically always
read from the $PKGDIR/Packages cache anyway. The cache is generated when
the package is built, and the rate-limiting step there is the building
of the package.

> Being in /tmp/ is only for commodity but the place is debatable.
> Instead the fact it _must_ be the first file it's not, in a sequential
> archive file like tar some things depend on it.

With the current approach, the xpak segment is not part of the tar file.
The tar file is compressed, and the xpak segment is appended to the end
of the resulting bzip2 file.

> seem to be the right time to do the change, since tool need to be
> rewritten anyway, but I'll leave to you analyze  the fallout of this change.

There will be zero benefits from doing that.
-- 
Thanks,
Zac