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1 files changed, 117 insertions, 0 deletions
diff --git a/usr/Kconfig b/usr/Kconfig
index bf8e8f15358f..6278f135256d 100644
--- a/usr/Kconfig
+++ b/usr/Kconfig
@@ -99,8 +99,125 @@ config RD_LZ4
Support loading of a LZ4 encoded initial ramdisk or cpio buffer
If unsure, say N.
+choice
+ prompt "Built-in initramfs compression mode"
+ depends on INITRAMFS_SOURCE!=""
+ optional
+ help
+ This option allows you to decide by which algorithm the builtin
+ initramfs will be compressed. Several compression algorithms are
+ available, which differ in efficiency, compression and
+ decompression speed. Compression speed is only relevant
+ when building a kernel. Decompression speed is relevant at
+ each boot. Also the memory usage during decompression may become
+ relevant on memory constrained systems. This is usually based on the
+ dictionary size of the algorithm with algorithms like XZ and LZMA
+ featuring large dictionary sizes.
+
+ High compression options are mostly useful for users who are
+ low on RAM, since it reduces the memory consumption during
+ boot.
+
+ Keep in mind that your build system needs to provide the appropriate
+ compression tool to compress the generated initram cpio file for
+ embedding.
+
+ If in doubt, select 'None'
+
+config INITRAMFS_COMPRESSION_NONE
+ bool "None"
+ help
+ Do not compress the built-in initramfs at all. This may sound wasteful
+ in space, but, you should be aware that the built-in initramfs will be
+ compressed at a later stage anyways along with the rest of the kernel,
+ on those architectures that support this. However, not compressing the
+ initramfs may lead to slightly higher memory consumption during a
+ short time at boot, while both the cpio image and the unpacked
+ filesystem image will be present in memory simultaneously
+
+config INITRAMFS_COMPRESSION_GZIP
+ bool "Gzip"
+ depends on RD_GZIP
+ help
+ Use the old and well tested gzip compression algorithm. Gzip provides
+ a good balance between compression ratio and decompression speed and
+ has a reasonable compression speed. It is also more likely to be
+ supported by your build system as the gzip tool is present by default
+ on most distros.
+
+config INITRAMFS_COMPRESSION_BZIP2
+ bool "Bzip2"
+ depends on RD_BZIP2
+ help
+ It's compression ratio and speed is intermediate. Decompression speed
+ is slowest among the choices. The initramfs size is about 10% smaller
+ with bzip2, in comparison to gzip. Bzip2 uses a large amount of
+ memory. For modern kernels you will need at least 8MB RAM or more for
+ booting.
+
+ If you choose this, keep in mind that you need to have the bzip2 tool
+ available to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_LZMA
+ bool "LZMA"
+ depends on RD_LZMA
+ help
+ This algorithm's compression ratio is best but has a large dictionary
+ size which might cause issues in memory constrained systems.
+ Decompression speed is between the other choices. Compression is
+ slowest. The initramfs size is about 33% smaller with LZMA in
+ comparison to gzip.
+
+ If you choose this, keep in mind that you may need to install the xz
+ or lzma tools to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_XZ
+ bool "XZ"
+ depends on RD_XZ
+ help
+ XZ uses the LZMA2 algorithm and has a large dictionary which may cause
+ problems on memory constrained systems. The initramfs size is about
+ 30% smaller with XZ in comparison to gzip. Decompression speed is
+ better than that of bzip2 but worse than gzip and LZO. Compression is
+ slow.
+
+ If you choose this, keep in mind that you may need to install the xz
+ tool to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_LZO
+ bool "LZO"
+ depends on RD_LZO
+ help
+ It's compression ratio is the second poorest amongst the choices. The
+ kernel size is about 10% bigger than gzip. Despite that, it's
+ decompression speed is the second fastest and it's compression speed
+ is quite fast too.
+
+ If you choose this, keep in mind that you may need to install the lzop
+ tool to be able to compress the initram.
+
+config INITRAMFS_COMPRESSION_LZ4
+ bool "LZ4"
+ depends on RD_LZ4
+ help
+ It's compression ratio is the poorest amongst the choices. The kernel
+ size is about 15% bigger than gzip; however its decompression speed
+ is the fastest.
+
+ If you choose this, keep in mind that most distros don't provide lz4
+ by default which could cause a build failure.
+
+endchoice
+
config INITRAMFS_COMPRESSION
string
+ default "" if INITRAMFS_COMPRESSION_NONE
+ default ".gz" if INITRAMFS_COMPRESSION_GZIP
+ default ".bz2" if INITRAMFS_COMPRESSION_BZIP2
+ default ".lzma" if INITRAMFS_COMPRESSION_LZMA
+ default ".xz" if INITRAMFS_COMPRESSION_XZ
+ default ".lzo" if INITRAMFS_COMPRESSION_LZO
+ default ".lz4" if INITRAMFS_COMPRESSION_LZ4
default ".gz" if RD_GZIP
default ".lz4" if RD_LZ4
default ".lzo" if RD_LZO