From: Nick Terrell <terrelln@xxxxxx> Please pull from git@xxxxxxxxxx:terrelln/linux.git tags/v8-zstd to get these changes. Alternatively the patchset is included. Hi all, This patch set adds support for a ZSTD-compressed kernel, ramdisk, and initramfs in the kernel boot process. ZSTD-compressed ramdisk and initramfs are supported on all architectures. The ZSTD-compressed kernel is only hooked up to x86 in this patch set. Zstandard requires slightly more memory during the kernel decompression on x86 (192 KB vs 64 KB), and the memory usage is independent of the window size. Zstandard requires memory proprortional to the window size used during compression for decompressing the ramdisk image, since streaming mode is used. Newer versions of zstd (1.3.2+) list the window size of a file with `zstd -lv <file>'. The absolute maximum amount of memory required is just over 8 MB, but it can be controlled at compression time. This patch set has been boot tested with buildroot and QEMU based off of linux-5.6-rc6. On i386 and x86_64 I have tested the following configurations: * zstd compressed kernel and a separate zstd compressed initramfs * zstd compressed kernel and a built-in zstd compressed initramfs * gzip compressed kernel and a separate gzip compressed initramfs * gzip compressed kernel and a built-in gzip compressed initramfs On arm and aarch64 I tested the same configurations, except that the kernel is always gzip compressed. Facebook has been using v1 of these patches on x86_64 devices for more than 6 months. When we switched from a xz compressed initramfs to a zstd compressed initramfs decompression time shrunk from 12 seconds to 3 seconds. When we switched from a xz compressed kernel to a zstd compressed kernel we saved 2 seconds of boot time. Facebook has been using v2 of these patches on aarch64 devices for a few weeks. When we switched from an lzma compressed initramfs to a zstd compressed initramfs decompression time shrunk from 27 seconds to 8 seconds. The zstd compressed kernel is smaller than the gzip compressed kernel but larger than the xz or lzma compressed kernels, and it decompresses faster than everything except lz4. See the table below for the measurement of an x86_64 kernel ordered by compressed size: algo size xz 6,509,792 lzma 6,856,576 zstd 7,399,157 gzip 8,522,527 bzip 8,629,603 lzo 9,808,035 lz4 10,705,570 none 32,565,672 Alex Xu ran benchmarks in https://lkml.org/lkml/2020/7/1/722. v1 -> v2: - Rebase - usr/Makefile and init/Kconfig were changed so the patches were updated - No functional changes except to rebase - Split the patches up into smaller chunks v2 -> v3: - Add *.zst to the .gitignore in patch 8 - Style nits in patch 3 - Rename the PREBOOT macro to ZSTD_PREBOOT and XXH_PREBOOT in patches 1 through 3 v3 -> v4: - Increase the ZSTD_IOBUF_SIZE from 4KB to 128KB to improve performance. With this change I switch from malloc() to large_malloc() for the buffers. - Increase the maximum allowed window size from 8 MB to 128 MB, which is the max that zstd in the kernel supports. v4 -> v5: - Update commit message for patch 6 in response to comments - Rebase onto next-20200408 v5 -> v6: - Rebase onto v5.8-rc4 v6 -> v7: - (1/7) Don't define or use 'ZSTD_PREBOOT' to hide exports - (2/8) Drop 'lib: prepare xxhash for preboot environment' - (2/7) Use '__DISABLE_EXPORTS' in unzstd to hide exports - (3/7) Update zstd compression cmd to follow other compressors - (3/7) Add zstd22 cmd - (6/7) Use zstd -22 --ultra (zstd22) for x86 kernel compression v7 -> v8: - (2/7) Don't define '__DISABLE_EXPORTS' - (6/7) Define '__DISABLE_EXPORTS' in misc.c Best, Nick Terrell Adam Borowski (1): .gitignore: add ZSTD-compressed files Nick Terrell (6): lib: prepare zstd for preboot environment lib: add zstd support to decompress init: add support for zstd compressed kernel usr: add support for zstd compressed initramfs x86: bump ZO_z_extra_bytes margin for zstd x86: Add support for ZSTD compressed kernel .gitignore | 1 + Documentation/x86/boot.rst | 6 +- Makefile | 3 +- arch/x86/Kconfig | 1 + arch/x86/boot/compressed/Makefile | 5 +- arch/x86/boot/compressed/misc.c | 9 + arch/x86/boot/header.S | 8 +- arch/x86/include/asm/boot.h | 6 +- include/linux/decompress/unzstd.h | 11 + init/Kconfig | 15 +- lib/Kconfig | 4 + lib/Makefile | 1 + lib/decompress.c | 5 + lib/decompress_unzstd.c | 344 ++++++++++++++++++++++++++++++ lib/zstd/fse_decompress.c | 9 +- lib/zstd/zstd_internal.h | 14 +- scripts/Makefile.lib | 22 ++ usr/Kconfig | 20 ++ usr/Makefile | 1 + 19 files changed, 466 insertions(+), 19 deletions(-) create mode 100644 include/linux/decompress/unzstd.h create mode 100644 lib/decompress_unzstd.c -- 2.27.0
