Patchwork linux: Do not force GZIP initramfs compression

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Submitter Valentine Barshak
Date Oct. 9, 2012, 11:34 p.m.
Message ID <1349825696-28535-1-git-send-email-gvaxon@gmail.com>
Download mbox | patch
Permalink /patch/190512/
State Accepted
Commit 391c82efa14d6db253f42616d970dacbe826b7d5
Headers show

Comments

Valentine Barshak - Oct. 9, 2012, 11:34 p.m.
Initramfs compression does not make much sense for the architectures
that support compressed kernel images because in this case the data
would be compressed twice. This will eventually result in a bigger
kernel image and time overhead when uncompressing it.
The only reason to use compressed initramfs is to reduce memory
usage when the kernel prepares rootfs, and both the unpacked
filesystem and initramfs.cpio are present in the memory.

Buildroot attempts to force GZIP compression for initramfs,
however it doesn't always work because initramfs compression mode
depends on RAM disk compression supported by the kernel.
Thus, CONFIG_INITRAMFS_COMPRESSION_GZIP depends on CONFIG_RD_GZIP.
If CONFIG_RD_GZIP is not set, setting GZIP initramfs compression
will have no effect.

Besides, the kernel also supports other compression methods,
like BZIP2, LZMA, XZ and LZO. Forcing the good old GZIP does not
really make much sense any more.

This removes initramfs compression settings from Buildroot,
so that the default value preset in the kernel config is used,
which is CONFIG_INITRAMFS_COMPRESSION_NONE.

If initramfs compression is still needed, it can be set
in the kernel config (using make linux-menuconfig)

Signed-off-by: Valentine Barshak <gvaxon@gmail.com>
---
 fs/initramfs/Config.in | 4 ++--
 linux/linux.mk         | 4 +---
 2 files changed, 3 insertions(+), 5 deletions(-)
Arnout Vandecappelle - Oct. 10, 2012, 7:26 a.m.
On 10/10/12 01:34, Valentine Barshak wrote:
> Initramfs compression does not make much sense for the architectures
> that support compressed kernel images because in this case the data
> would be compressed twice. This will eventually result in a bigger
> kernel image and time overhead when uncompressing it.
> The only reason to use compressed initramfs is to reduce memory
> usage when the kernel prepares rootfs, and both the unpacked
> filesystem and initramfs.cpio are present in the memory.
>
> Buildroot attempts to force GZIP compression for initramfs,
> however it doesn't always work because initramfs compression mode
> depends on RAM disk compression supported by the kernel.
> Thus, CONFIG_INITRAMFS_COMPRESSION_GZIP depends on CONFIG_RD_GZIP.
> If CONFIG_RD_GZIP is not set, setting GZIP initramfs compression
> will have no effect.
>
> Besides, the kernel also supports other compression methods,
> like BZIP2, LZMA, XZ and LZO. Forcing the good old GZIP does not
> really make much sense any more.
>
> This removes initramfs compression settings from Buildroot,
> so that the default value preset in the kernel config is used,
> which is CONFIG_INITRAMFS_COMPRESSION_NONE.
>
> If initramfs compression is still needed, it can be set
> in the kernel config (using make linux-menuconfig)
>
> Signed-off-by: Valentine Barshak<gvaxon@gmail.com>

Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

  I especially like the extensive commit message!

  Regards,
  Arnout
Kelvin Cheung - July 8, 2013, 6:44 a.m.
Agreed.

2012/10/10 Arnout Vandecappelle <arnout@mind.be>

> On 10/10/12 01:34, Valentine Barshak wrote:
>
>> Initramfs compression does not make much sense for the architectures
>> that support compressed kernel images because in this case the data
>> would be compressed twice. This will eventually result in a bigger
>> kernel image and time overhead when uncompressing it.
>> The only reason to use compressed initramfs is to reduce memory
>> usage when the kernel prepares rootfs, and both the unpacked
>> filesystem and initramfs.cpio are present in the memory.
>>
>> Buildroot attempts to force GZIP compression for initramfs,
>> however it doesn't always work because initramfs compression mode
>> depends on RAM disk compression supported by the kernel.
>> Thus, CONFIG_INITRAMFS_COMPRESSION_**GZIP depends on CONFIG_RD_GZIP.
>> If CONFIG_RD_GZIP is not set, setting GZIP initramfs compression
>> will have no effect.
>>
>> Besides, the kernel also supports other compression methods,
>> like BZIP2, LZMA, XZ and LZO. Forcing the good old GZIP does not
>> really make much sense any more.
>>
>> This removes initramfs compression settings from Buildroot,
>> so that the default value preset in the kernel config is used,
>> which is CONFIG_INITRAMFS_COMPRESSION_**NONE.
>>
>> If initramfs compression is still needed, it can be set
>> in the kernel config (using make linux-menuconfig)
>>
>> Signed-off-by: Valentine Barshak<gvaxon@gmail.com>
>>
>
> Acked-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
>
>  I especially like the extensive commit message!
>
>  Regards,
>  Arnout
> --
> Arnout Vandecappelle                               arnout at mind be
> Senior Embedded Software Architect                 +32-16-286540
> Essensium/Mind                                     http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium                BE 872 984 063 RPR
> Leuven
> LinkedIn profile: http://www.linkedin.com/in/**arnoutvandecappelle<http://www.linkedin.com/in/arnoutvandecappelle>
> GPG fingerprint:  7CB5 E4CC 6C2E EFD4 6E3D A754 F963 ECAB 2450 2F1F
>
> ______________________________**_________________
> buildroot mailing list
> buildroot@busybox.net
> http://lists.busybox.net/**mailman/listinfo/buildroot<http://lists.busybox.net/mailman/listinfo/buildroot>
>
Peter Korsgaard - July 8, 2013, 12:57 p.m.
>>>>> "Valentine" == Valentine Barshak <gvaxon@gmail.com> writes:

 Valentine> Initramfs compression does not make much sense for the architectures
 Valentine> that support compressed kernel images because in this case the data
 Valentine> would be compressed twice. This will eventually result in a bigger
 Valentine> kernel image and time overhead when uncompressing it.
 Valentine> The only reason to use compressed initramfs is to reduce memory
 Valentine> usage when the kernel prepares rootfs, and both the unpacked
 Valentine> filesystem and initramfs.cpio are present in the memory.

 Valentine> Buildroot attempts to force GZIP compression for initramfs,
 Valentine> however it doesn't always work because initramfs compression mode
 Valentine> depends on RAM disk compression supported by the kernel.
 Valentine> Thus, CONFIG_INITRAMFS_COMPRESSION_GZIP depends on CONFIG_RD_GZIP.
 Valentine> If CONFIG_RD_GZIP is not set, setting GZIP initramfs compression
 Valentine> will have no effect.

 Valentine> Besides, the kernel also supports other compression methods,
 Valentine> like BZIP2, LZMA, XZ and LZO. Forcing the good old GZIP does not
 Valentine> really make much sense any more.

 Valentine> This removes initramfs compression settings from Buildroot,
 Valentine> so that the default value preset in the kernel config is used,
 Valentine> which is CONFIG_INITRAMFS_COMPRESSION_NONE.

 Valentine> If initramfs compression is still needed, it can be set
 Valentine> in the kernel config (using make linux-menuconfig)

Sorry, this somehow seems to have fallen through the cracks - Committed,
thanks.

Patch

diff --git a/fs/initramfs/Config.in b/fs/initramfs/Config.in
index bbc2ab0..b71018e 100644
--- a/fs/initramfs/Config.in
+++ b/fs/initramfs/Config.in
@@ -9,8 +9,8 @@  config BR2_TARGET_ROOTFS_INITRAMFS
 
 	  A rootfs.cpio file will be generated in the images/ directory.
 	  This is the archive that will be included in the kernel image.
-	  The rootfs in the kernel will always be gzip'ed, regardless
-	  of how buildroot's cpio archive is configured.
+	  The default rootfs compression set in the kernel configuration
+	  is used, regardless of how buildroot's cpio archive is configured.
 
 	  Note that enabling initramfs together with another filesystem
 	  formats doesn't make sense: you would end up having two
diff --git a/linux/linux.mk b/linux/linux.mk
index c4bdf90..914c09a 100644
--- a/linux/linux.mk
+++ b/linux/linux.mk
@@ -169,9 +169,7 @@  define LINUX_CONFIGURE_CMDS
 		$(call KCONFIG_ENABLE_OPT,CONFIG_BLK_DEV_INITRD,$(@D)/.config)
 		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_SOURCE,\"$(BINARIES_DIR)/rootfs.cpio\",$(@D)/.config)
 		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_UID,0,$(@D)/.config)
-		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_GID,0,$(@D)/.config)
-		$(call KCONFIG_DISABLE_OPT,CONFIG_INITRAMFS_COMPRESSION_NONE,$(@D)/.config)
-		$(call KCONFIG_ENABLE_OPT,CONFIG_INITRAMFS_COMPRESSION_GZIP,$(@D)/.config))
+		$(call KCONFIG_SET_OPT,CONFIG_INITRAMFS_ROOT_GID,0,$(@D)/.config))
 	$(if $(BR2_ROOTFS_DEVICE_CREATION_STATIC),,
 		$(call KCONFIG_ENABLE_OPT,CONFIG_DEVTMPFS,$(@D)/.config)
 		$(call KCONFIG_ENABLE_OPT,CONFIG_DEVTMPFS_MOUNT,$(@D)/.config))