linux-kernel - Re: [PATCH 2/3] kbuild: handle module compression while running 'make modules

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Date:	Thu, 21 Aug 2014 01:39:59 +0930
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Bertrand Jacquin <beber@...eeweb.net>, linux-kbuild@...r.kernel.org
Cc:	Bertrand Jacquin <beber@...eeweb.net>,
	linux-kernel@...r.kernel.org, Willy Tarreau <w@....eu>
Subject: Re: [PATCH 2/3] kbuild: handle module compression while running 'make modules_install'.

Bertrand Jacquin <beber@...eeweb.net> writes:

> 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@....eu>
> Signed-off-by: Bertrand Jacquin <beber@...eeweb.net>

Thanks, applied these two as well.  They'll go in *next* merge window
(ie. 3.18).

Cheers.
Rusty.
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