From beb50df39e91745604ce3cb9dc6a503f39f4383d Mon Sep 17 00:00:00 2001 From: Bertrand Jacquin Date: Wed, 27 Aug 2014 20:31:56 +0930 Subject: kbuild: handle module compression while running 'make modules_install'. 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 Signed-off-by: Bertrand Jacquin Signed-off-by: Rusty Russell --- init/Kconfig | 43 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) (limited to 'init') diff --git a/init/Kconfig b/init/Kconfig index e84c6423a2e5..4980925bf348 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1906,6 +1906,49 @@ config MODULE_SIG_HASH default "sha384" if MODULE_SIG_SHA384 default "sha512" if MODULE_SIG_SHA512 +config MODULE_COMPRESS + bool "Compress modules on installation" + depends on MODULES + help + This option compresses the kernel modules when 'make + modules_install' is run. + + The modules will be compressed either using gzip or xz depend on the + choice made in "Compression algorithm". + + module-init-tools has support for gzip format while kmod handle gzip + and xz compressed modules. + + When a kernel module is installed from outside of the main kernel + source and uses the Kbuild system for installing modules then that + kernel module will also be compressed when it is installed. + + This option provides little benefit when the modules are to be used inside + an initrd or initramfs, it generally is more efficient to compress the whole + initrd or initramfs instead. + + 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. + +choice + prompt "Compression algorithm" + depends on MODULE_COMPRESS + default MODULE_COMPRESS_GZIP + help + This determines which sort of compression will be used during + 'make modules_install'. + + GZIP (default) and XZ are supported. + +config MODULE_COMPRESS_GZIP + bool "GZIP" + +config MODULE_COMPRESS_XZ + bool "XZ" + +endchoice + endif # MODULES config INIT_ALL_POSSIBLE -- cgit v1.2.3-59-g8ed1b