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zstd/contrib/linux-kernel
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Nick Terrell 1eba76a2d1 [linux-kernel] Don't add -O3 to CFLAGS 
It is no longer necessary to get good performance, there is only a small
speed difference between -O2 and -O3, so just stick to the default of
-O2.

This also fixes the stack space usage on parisc. The compiler was buggy
for -O3 and used ~3KB of stack space for several functions. With -O2 the
problem is completely resolved, and stack space is back to a few hundred
bytes.

Additionally, we get a large code size win on gcc:

| Compiler | Before (Bytes) | After (Bytes) | Delta (Bytes) |
|----------|----------------|---------------|---------------|
| gcc-11   |         952754 |        738954 |       -213800 |
| clang-12 |         976290 |        938826 |        -37464 |
2021-11-16 14:29:35 -08:00
..
test [linux-kernel] Don't inline function in zstd_opt.c 2021-11-15 20:37:58 -08:00
.gitignore fix gitignore 2017-04-04 18:15:21 -07:00
btrfs-benchmark.sh Add BtrFS benchmarks 2017-04-11 12:40:53 -07:00
btrfs-extract-benchmark.sh [linux] Write all the patch summaries 2017-06-21 20:23:44 -07:00
decompress_sources.h [contrib][linux] Fix up SPDX license identifiers 2021-09-22 15:06:08 -07:00
linux.mk [linux-kernel] Don't add -O3 to CFLAGS 2021-11-16 14:29:35 -08:00
linux_zstd.h [contrib][linux] Fix up SPDX license identifiers 2021-09-22 15:06:08 -07:00
Makefile [linux-kernel] Don't inline function in zstd_opt.c 2021-11-15 20:37:58 -08:00
mem.h [contrib][linux] Fix up SPDX license identifiers 2021-09-22 15:06:08 -07:00
README.md [linux-kernel] Update README with initial instructions on how to update zstd in the kernel 2020-09-09 14:36:22 -07:00
squashfs-benchmark.sh [kernel] Update README with SquashFS patch 2017-05-03 11:07:39 -07:00
zstd_compress_module.c [contrib][linux] Reduce stack usage by 80 bytes 2021-09-22 18:18:20 -07:00
zstd_decompress_module.c [contrib][linux] Fix up SPDX license identifiers 2021-09-22 15:06:08 -07:00
zstd_deps.h [contrib][linux] Fix up SPDX license identifiers 2021-09-22 15:06:08 -07:00

README.md

Zstd in the Linux Kernel

This directory contains the scripts needed to transform upstream zstd into the version imported into the kernel. All the transforms are automated and tested by our continuous integration.

Upgrading Zstd in the Linux Kernel

  1. cd into this directory.
  2. Run make libzstd and read the output. Make sure that all the diffs printed and changes made by the script are correct.
  3. Run make test and ensure that it passes.
  4. Import zstd into the Linux Kernel make import LINUX=/path/to/linux/repo
  5. Inspect the diff for sanity.
  6. Check the Linux Kernel history for zstd. If any patches were made to the kernel version of zstd, but not to upstream zstd, then port them upstream if necessary.
  7. Test the diff. Benchmark if necessary. Make sure to test multiple architectures: At least x86, i386, and arm.
  8. Submit the patch to the LKML.