[PATCH v9 4/7] usr: add support for zstd compressed initramfs
From: Nick Terrell
Date: Mon Jul 27 2020 - 19:11:08 EST
From: Nick Terrell <terrelln@xxxxxx>
* 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,
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
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Signed-off-by: Nick Terrell <terrelln@xxxxxx>
usr/Kconfig | 20 ++++++++++++++++++++
usr/Makefile | 1 +
2 files changed, 21 insertions(+)
diff --git a/usr/Kconfig b/usr/Kconfig
index 96afb03b65f9..2599bc21c1b2 100644
@@ -100,6 +100,15 @@ config RD_LZ4
Support loading of a LZ4 encoded initial ramdisk or cpio buffer
If unsure, say N.
+ bool "Support initial ramdisk/ramfs compressed using ZSTD"
+ default y
+ depends on BLK_DEV_INITRD
+ select DECOMPRESS_ZSTD
+ Support loading of a ZSTD encoded initial ramdisk or cpio buffer.
+ If unsure, say N.
prompt "Built-in initramfs compression mode"
depends on INITRAMFS_SOURCE != ""
@@ -196,6 +205,17 @@ config INITRAMFS_COMPRESSION_LZ4
If you choose this, keep in mind that most distros don't provide lz4
by default which could cause a build failure.
+ bool "ZSTD"
+ depends on RD_ZSTD
+ 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.
diff --git a/usr/Makefile b/usr/Makefile
index c12e6b15ce72..b1a81a40eab1 100644
@@ -15,6 +15,7 @@ compress-$(CONFIG_INITRAMFS_COMPRESSION_LZMA) := lzma
compress-$(CONFIG_INITRAMFS_COMPRESSION_XZ) := xzmisc
compress-$(CONFIG_INITRAMFS_COMPRESSION_LZO) := lzo
compress-$(CONFIG_INITRAMFS_COMPRESSION_LZ4) := lz4
+compress-$(CONFIG_INITRAMFS_COMPRESSION_ZSTD) := zstd
obj-$(CONFIG_BLK_DEV_INITRD) := initramfs_data.o