Re: [PATCH] use gzip compression with --no-name to create identicals steps backups

["Yann E. MORIN" <yann dot morin dot 1998 at anciens dot enib dot fr>]

Bruno, All,

On Thursday 18 March 2010 17:47:27 Bruno Tarquini wrote:
> use gzip compression with --no-name to create identicals steps backups.
> So backups created from an identical directory are really identicals.
> Calling gzip by passing '-z' to tar is not good enough: by default, gzip
> saves the archive's mtime as metadata (--name) and preventing us to generate
> the exact same state when no files have been modified between the two steps.
> Later, by removing the duplicates files, it will be possible to
> decreasing the backup directory to around 20% of it actual size.

Oh! You mean you want to (hard|sym)link the tarballs when their contents
are the same, to save space, right?

Eg. the prefix backup tarball has the same content for cc_core_pass_1 and
for elf2flt.

What you have to know is that the backup tarballs for each steps are only
for debug purposes, when it is needed to restart a build when trying to
fix an issue in a specific step, to avoid re-building all from scratch
every time. And when the toolchain finally got build, you get safely
get rid of those backup tarballs! Also, rebuildign the toolchain without
saving the tarballs will make for a clean build.log.

In fact, even I seldom use that feature nowadays.

Just for information, here is the space it takes to store the backup
tarballs for the armeb-unknown-linux-gnueabi sample:

# du -hs src/ tarballs/ tools/          \
     armeb-unknown-linux-gnueabi/state/ \
     armeb-unknown-linux-gnueabi/build/ \
     .
1.5G    src/
184M    tarballs/
28K     tools/
1.4G    armeb-unknown-linux-gnueabi/state/
1.6G    armeb-unknown-linux-gnueabi/build/
4.5G    .

Which means that the backup tarballs are just less than one third of the
total space used to build the toolchain (not counting the 450MiB used by
the toolchain itself, in which case the backup tarballs account for
roughly 1/4th of the total space).

Are you *that* short of space that you need this feature when *debugging*
crosstool-NG ?

Which basicaly boils down to: what do you want the backup tarballs for?

> At the same time, we pass -3 to gzip as it is said in Kbuild help.

Not needed. -3 is the default for gzip compression.

Regards,
Yann E. MORIN.

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