xz: adjust arch-specific options for better kernel compression
Use LZMA2 options that match the arch-specific alignment of instructions. This change reduces compressed kernel size 0-2 % depending on the arch. On 1-byte-aligned x86 it makes no difference and on 4-byte-aligned archs it helps the most. Use the ARM-Thumb filter for ARM-Thumb2 kernels. This reduces compressed kernel size about 5 %.[1] Previously such kernels were compressed using the ARM filter which didn't do anything useful with ARM-Thumb2 code. Add BCJ filter support for ARM64 and RISC-V. Compared to unfiltered XZ or plain LZMA, the compressed kernel size is reduced about 5 % on ARM64 and 7 % on RISC-V. A new enough version of the xz tool is required: 5.4.0 for ARM64 and 5.6.0 for RISC-V. With an old xz version, a message is printed to standard error and the kernel is compressed without the filter. Update lib/decompress_unxz.c to match the changes to xz_wrap.sh. Update the CONFIG_KERNEL_XZ help text in init/Kconfig: - Add the RISC-V and ARM64 filters. - Clarify that the PowerPC filter is for big endian only. - Omit IA-64. Link: https://lore.kernel.org/lkml/1637379771-39449-1-git-send-email-zhongjubin@huawei.com/ [1] Link: https://lkml.kernel.org/r/20240721133633.47721-15-lasse.collin@tukaani.org Signed-off-by: Lasse Collin <lasse.collin@tukaani.org> Reviewed-by: Sam James <sam@gentoo.org> Cc: Simon Glass <sjg@chromium.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Paul Walmsley <paul.walmsley@sifive.com> Cc: Palmer Dabbelt <palmer@dabbelt.com> Cc: Albert Ou <aou@eecs.berkeley.edu> Cc: Jubin Zhong <zhongjubin@huawei.com> Cc: Jules Maselbas <jmaselbas@zdiv.net> Cc: Emil Renner Berthing <emil.renner.berthing@canonical.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Joel Stanley <joel@jms.id.au> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Krzysztof Kozlowski <krzk@kernel.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Rui Li <me@lirui.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lasse Collin
Andrew Morton
parent
8653c90992
commit
7472ff8ada
@ -310,8 +310,9 @@ config KERNEL_XZ
|
||||
BCJ filters which can improve compression ratio of executable
|
||||
code. The size of the kernel is about 30% smaller with XZ in
|
||||
comparison to gzip. On architectures for which there is a BCJ
|
||||
filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
|
||||
will create a few percent smaller kernel than plain LZMA.
|
||||
filter (i386, x86_64, ARM, ARM64, RISC-V, big endian PowerPC,
|
||||
and SPARC), XZ will create a few percent smaller kernel than
|
||||
plain LZMA.
|
||||
|
||||
The speed is about the same as with LZMA: The decompression
|
||||
speed of XZ is better than that of bzip2 but worse than gzip
|
||||
|
||||
@ -126,11 +126,21 @@
|
||||
#ifdef CONFIG_X86
|
||||
# define XZ_DEC_X86
|
||||
#endif
|
||||
#ifdef CONFIG_PPC
|
||||
#if defined(CONFIG_PPC) && defined(CONFIG_CPU_BIG_ENDIAN)
|
||||
# define XZ_DEC_POWERPC
|
||||
#endif
|
||||
#ifdef CONFIG_ARM
|
||||
# define XZ_DEC_ARM
|
||||
# ifdef CONFIG_THUMB2_KERNEL
|
||||
# define XZ_DEC_ARMTHUMB
|
||||
# else
|
||||
# define XZ_DEC_ARM
|
||||
# endif
|
||||
#endif
|
||||
#ifdef CONFIG_ARM64
|
||||
# define XZ_DEC_ARM64
|
||||
#endif
|
||||
#ifdef CONFIG_RISCV
|
||||
# define XZ_DEC_RISCV
|
||||
#endif
|
||||
#ifdef CONFIG_SPARC
|
||||
# define XZ_DEC_SPARC
|
||||
|
||||
@ -6,14 +6,146 @@
|
||||
#
|
||||
# Author: Lasse Collin <lasse.collin@tukaani.org>
|
||||
|
||||
BCJ=
|
||||
LZMA2OPTS=
|
||||
# This has specialized settings for the following archs. However,
|
||||
# XZ-compressed kernel isn't currently supported on every listed arch.
|
||||
#
|
||||
# Arch Align Notes
|
||||
# arm 2/4 ARM and ARM-Thumb2
|
||||
# arm64 4
|
||||
# csky 2
|
||||
# loongarch 4
|
||||
# mips 2/4 MicroMIPS is 2-byte aligned
|
||||
# parisc 4
|
||||
# powerpc 4 Uses its own wrapper for compressors instead of this.
|
||||
# riscv 2/4
|
||||
# s390 2
|
||||
# sh 2
|
||||
# sparc 4
|
||||
# x86 1
|
||||
|
||||
# A few archs use 2-byte or 4-byte aligned instructions depending on
|
||||
# the kernel config. This function is used to check if the relevant
|
||||
# config option is set to "y".
|
||||
is_enabled()
|
||||
{
|
||||
grep -q "^$1=y$" include/config/auto.conf
|
||||
}
|
||||
|
||||
# XZ_VERSION is needed to disable features that aren't available in
|
||||
# old XZ Utils versions.
|
||||
XZ_VERSION=$($XZ --robot --version) || exit
|
||||
XZ_VERSION=$(printf '%s\n' "$XZ_VERSION" | sed -n 's/^XZ_VERSION=//p')
|
||||
|
||||
# Assume that no BCJ filter is available.
|
||||
BCJ=
|
||||
|
||||
# Set the instruction alignment to 1, 2, or 4 bytes.
|
||||
#
|
||||
# Set the BCJ filter if one is available.
|
||||
# It must match the #ifdef usage in lib/decompress_unxz.c.
|
||||
case $SRCARCH in
|
||||
x86) BCJ=--x86 ;;
|
||||
powerpc) BCJ=--powerpc ;;
|
||||
arm) BCJ=--arm ;;
|
||||
sparc) BCJ=--sparc ;;
|
||||
arm)
|
||||
if is_enabled CONFIG_THUMB2_KERNEL; then
|
||||
ALIGN=2
|
||||
BCJ=--armthumb
|
||||
else
|
||||
ALIGN=4
|
||||
BCJ=--arm
|
||||
fi
|
||||
;;
|
||||
|
||||
arm64)
|
||||
ALIGN=4
|
||||
|
||||
# ARM64 filter was added in XZ Utils 5.4.0.
|
||||
if [ "$XZ_VERSION" -ge 50040002 ]; then
|
||||
BCJ=--arm64
|
||||
else
|
||||
echo "$0: Upgrading to xz >= 5.4.0" \
|
||||
"would enable the ARM64 filter" \
|
||||
"for better compression" >&2
|
||||
fi
|
||||
;;
|
||||
|
||||
csky)
|
||||
ALIGN=2
|
||||
;;
|
||||
|
||||
loongarch)
|
||||
ALIGN=4
|
||||
;;
|
||||
|
||||
mips)
|
||||
if is_enabled CONFIG_CPU_MICROMIPS; then
|
||||
ALIGN=2
|
||||
else
|
||||
ALIGN=4
|
||||
fi
|
||||
;;
|
||||
|
||||
parisc)
|
||||
ALIGN=4
|
||||
;;
|
||||
|
||||
powerpc)
|
||||
ALIGN=4
|
||||
|
||||
# The filter is only for big endian instruction encoding.
|
||||
if is_enabled CONFIG_CPU_BIG_ENDIAN; then
|
||||
BCJ=--powerpc
|
||||
fi
|
||||
;;
|
||||
|
||||
riscv)
|
||||
if is_enabled CONFIG_RISCV_ISA_C; then
|
||||
ALIGN=2
|
||||
else
|
||||
ALIGN=4
|
||||
fi
|
||||
|
||||
# RISC-V filter was added in XZ Utils 5.6.0.
|
||||
if [ "$XZ_VERSION" -ge 50060002 ]; then
|
||||
BCJ=--riscv
|
||||
else
|
||||
echo "$0: Upgrading to xz >= 5.6.0" \
|
||||
"would enable the RISC-V filter" \
|
||||
"for better compression" >&2
|
||||
fi
|
||||
;;
|
||||
|
||||
s390)
|
||||
ALIGN=2
|
||||
;;
|
||||
|
||||
sh)
|
||||
ALIGN=2
|
||||
;;
|
||||
|
||||
sparc)
|
||||
ALIGN=4
|
||||
BCJ=--sparc
|
||||
;;
|
||||
|
||||
x86)
|
||||
ALIGN=1
|
||||
BCJ=--x86
|
||||
;;
|
||||
|
||||
*)
|
||||
echo "$0: Arch-specific tuning is missing for '$SRCARCH'" >&2
|
||||
|
||||
# Guess 2-byte-aligned instructions. Guessing too low
|
||||
# should hurt less than guessing too high.
|
||||
ALIGN=2
|
||||
;;
|
||||
esac
|
||||
|
||||
# Select the LZMA2 options matching the instruction alignment.
|
||||
case $ALIGN in
|
||||
1) LZMA2OPTS= ;;
|
||||
2) LZMA2OPTS=lp=1 ;;
|
||||
4) LZMA2OPTS=lp=2,lc=2 ;;
|
||||
*) echo "$0: ALIGN wrong or missing" >&2; exit 1 ;;
|
||||
esac
|
||||
|
||||
# Use single-threaded mode because it compresses a little better
|
||||
|
||||
Loading…
Reference in New Issue
Block a user