Re: [GIT PULL][PATCH v6 0/8] Add support for ZSTD-compressed kernel and initramfs

Sedat Dilek
2020-07-07T09:01:40Z

On Tue, Jul 7, 2020 at 6:03 AM Sedat Dilek <sedat.dilek@gmail.com> wrote:
>
> On Tue, Jul 7, 2020 at 5:50 AM Nick Terrell <nickrterrell@gmail.com> wrote:
> >
> > From: Nick Terrell <terrelln@fb.com>
> >
> > Please pull from
> >
> > git@github.com:terrelln/linux.git tags/v6-zstd
> >
> > to get these changes. Alternatively the patchset is included.
> >
>
> Hi Nick,
>
> cool, I just pulled from their.
> Yesterday, I switched over from Linux v5.7.y to v5.8-rc4.
> What a good timing :-).
>
> I will report later.
>

Looks good.

$ scripts/diffconfig /boot/config-5.8.0-rc4-3-amd64-llvm11-ias
/boot/config-5.8.0-rc4-4-amd64-llvm11-ias
BUILD_SALT "5.8.0-rc4-3-amd64-llvm11-ias" -> "5.8.0-rc4-4-amd64-llvm11-ias"
KERNEL_XZ y -> n
+DECOMPRESS_ZSTD y
+HAVE_KERNEL_ZSTD y
+KERNEL_ZSTD y
+RD_ZSTD y

# du -s -k initrd.img-5.8.0-rc4-3-amd64-llvm11-ias
initrd.img-5.8.0-rc4-4-amd64-llvm11-ias
31208 initrd.img-5.8.0-rc4-3-amd64-llvm11-ias <--- GZIP
24768 initrd.img-5.8.0-rc4-4-amd64-llvm11-ias <--- ZSTD

- Sedat -

> Regards,
> - Sedat -
>
> > 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-5.8-rc4.
> >
> > 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
> >
> > Best,
> > Nick Terrell
> >
> > Adam Borowski (1):
> > .gitignore: add ZSTD-compressed files
> >
> > Nick Terrell (7):
> > lib: prepare zstd for preboot environment
> > lib: prepare xxhash 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 +-
> > arch/x86/Kconfig | 1 +
> > arch/x86/boot/compressed/Makefile | 5 +-
> > arch/x86/boot/compressed/misc.c | 4 +
> > 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 | 342 ++++++++++++++++++++++++++++++
> > lib/xxhash.c | 21 +-
> > lib/zstd/decompress.c | 2 +
> > lib/zstd/fse_decompress.c | 9 +-
> > lib/zstd/zstd_internal.h | 14 +-
> > scripts/Makefile.lib | 15 ++
> > usr/Kconfig | 20 ++
> > usr/Makefile | 1 +
> > 20 files changed, 464 insertions(+), 27 deletions(-)
> > create mode 100644 include/linux/decompress/unzstd.h
> > create mode 100644 lib/decompress_unzstd.c
> >
> > --
> > 2.27.0
> >