usr: Add support for zstd compressed initramfs
- Add support for a zstd compressed initramfs.
- Add compression for compressing built-in initramfs with zstd.
I have tested this patch by boot testing with buildroot and QEMU.
Specifically, I booted the kernel with both a zstd and gzip compressed
initramfs, both built into the kernel and separate. I ensured that the
correct compression algorithm was used. I tested on arm, aarch64, i386,
and x86_64.
This patch has been tested in production on aarch64 and x86_64 devices.
Additionally, I have performance measurements from internal use in
production. On an aarch64 device we saw 19 second boot time improvement
from switching from lzma to zstd (27 seconds to 8 seconds). On an x86_64
device we saw a 9 second boot time reduction from switching from xz to
zstd.
Signed-off-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200730190841.2071656-5-nickrterrell@gmail.com
diff --git a/usr/Kconfig b/usr/Kconfig
index 96afb03..2599bc2 100644
--- a/usr/Kconfig
+++ b/usr/Kconfig
@@ -100,6 +100,15 @@
Support loading of a LZ4 encoded initial ramdisk or cpio buffer
If unsure, say N.
+config RD_ZSTD
+ bool "Support initial ramdisk/ramfs compressed using ZSTD"
+ default y
+ depends on BLK_DEV_INITRD
+ select DECOMPRESS_ZSTD
+ help
+ Support loading of a ZSTD encoded initial ramdisk or cpio buffer.
+ If unsure, say N.
+
choice
prompt "Built-in initramfs compression mode"
depends on INITRAMFS_SOURCE != ""
@@ -196,6 +205,17 @@
If you choose this, keep in mind that most distros don't provide lz4
by default which could cause a build failure.
+config INITRAMFS_COMPRESSION_ZSTD
+ bool "ZSTD"
+ depends on RD_ZSTD
+ help
+ ZSTD is a compression algorithm targeting intermediate compression
+ with fast decompression speed. It will compress better than GZIP and
+ decompress around the same speed as LZO, but slower than LZ4.
+
+ If you choose this, keep in mind that you may need to install the zstd
+ tool to be able to compress the initram.
+
config INITRAMFS_COMPRESSION_NONE
bool "None"
help