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kbuild: handle module compression while running 'make modules_install'.

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Since module-init-tools (gzip) and kmod (gzip and xz) support compressed
modules, it could be useful to include a support for compressing modules
right after having them installed. Doing this in kbuild instead of per
distro can permit to make this kind of usage more generic.

This patch add a Kconfig entry to "Enable loadable module support" menu
and let you choose to compress using gzip (default) or xz.

Both gzip and xz does not used any extra -[1-9] option since Andi Kleen
and Rusty Russell prove no gain is made using them. gzip is called with -n
argument to avoid storing original filename inside compressed file, that
way we can save some more bytes.

On a v3.16 kernel, 'make allmodconfig' generated 4680 modules for a
total of 378MB (no strip, no sign, no compress), the following table
shows observed disk space gain based on the allmodconfig .config :

       |           time                |
       +-------------+-----------------+
       | manual .ko  |       make      | size | percent
       | compression | modules_install |      | gain
       +-------------+-----------------+------+--------
  -    |             |     18.61s      | 378M |
  GZIP |   3m16s     |     3m37s       | 102M | 73.41%
  XZ   |   5m22s     |     5m39s       |  77M | 79.83%

The gain for restricted environnement seems to be interesting while
uncompress can be time consuming but happens only while loading a module,
that is generally done only once.

This is fully compatible with signed modules while the signed module is
compressed. module-init-tools or kmod handles decompression
and provide to other layer the uncompressed but signed payload.

Reviewed-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Bertrand Jacquin <beber@meleeweb.net>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Bertrand Jacquin 2014-08-27 20:31:56 +09:30 • committed by Rusty Russell
parent 40e42f6a25
commit beb50df39e
3 changed files with 60 additions and 1 deletions
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3
scripts/Makefile.modinst
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@ -22,7 +22,8 @@ quiet_cmd_modules_install = INSTALL $@
mkdir -p $(2) ; \
cp $@ $(2) ; \
$(mod_strip_cmd) $(2)/$(notdir $@) ; \
$(mod_sign_cmd) $(2)/$(notdir $@) $(patsubst %,|| true,$(KBUILD_EXTMOD))
$(mod_sign_cmd) $(2)/$(notdir $@) $(patsubst %,|| true,$(KBUILD_EXTMOD)) ; \
$(mod_compress_cmd) $(2)/$(notdir $@)
# Modules built outside the kernel source tree go into extra by default
INSTALL_MOD_DIR ?= extra