-# Linux Kernel Patch
+# Zstd in the Linux Kernel
-There are four pieces, the `xxhash` kernel module, the `zstd_compress` and `zstd_decompress` kernel modules, the BtrFS patch, and the SquashFS patch.
-The patches are based off of the linux kernel master branch.
+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.
-## xxHash kernel module
+## Upgrading Zstd in the Linux Kernel
-* The patch is located in `xxhash.diff`.
-* The header is in `include/linux/xxhash.h`.
-* The source is in `lib/xxhash.c`.
-* `test/XXHashUserLandTest.cpp` contains tests for the patch in userland by mocking the kernel headers.
- I tested the tests by commenting a line of of each branch in `xxhash.c` one line at a time, and made sure the tests failed.
- It can be run with the following commands:
- ```
- cd test && make googletest && make XXHashUserLandTest && ./XXHashUserLandTest
- ```
-* I also benchmarked the `xxhash` module against upstream xxHash, and made sure that they ran at the same speed.
-
-## Zstd Kernel modules
-
-* The (large) patch is located in `zstd.diff`, which depends on `xxhash.diff`.
-* The header is in `include/linux/zstd.h`.
-* It is split up into `zstd_compress` and `zstd_decompress`, which can be loaded independently.
-* Source files are in `lib/zstd/`.
-* `lib/Kconfig` and `lib/Makefile` need to be modified by applying `lib/Kconfig.diff` and `lib/Makefile.diff` respectively.
- These changes are also included in the `zstd.diff`.
-* `test/UserlandTest.cpp` contains tests for the patch in userland by mocking the kernel headers.
- It can be run with the following commands:
- ```
- cd test && make googletest && make UserlandTest && ./UserlandTest
- ```
-
-## BtrFS
-
-* The patch is located in `btrfs.diff`.
-* Additionally `fs/btrfs/zstd.c` is provided as a source for convenience.
-* The patch seems to be working, it doesn't crash the kernel, and compresses at speeds and ratios that are expected.
- It could still use some more testing for fringe features, like printing options.
-
-### Benchmarks
-
-Benchmarks run on a Ubuntu 14.04 with 2 cores and 4 GiB of RAM.
-The VM is running on a Macbook Pro with a 3.1 GHz Intel Core i7 processor,
-16 GB of ram, and a SSD.
-The kernel running was built from the master branch with the patch.
-
-The compression benchmark is copying 10 copies of the
-unzipped [silesia corpus](http://mattmahoney.net/dc/silesia.html) into a BtrFS
-filesystem mounted with `-o compress-force={none, lzo, zlib, zstd}`.
-The decompression benchmark is timing how long it takes to `tar` all 10 copies
-into `/dev/null`.
-The compression ratio is measured by comparing the output of `df` and `du`.
-See `btrfs-benchmark.sh` for details.
-
-| Algorithm | Compression ratio | Compression speed | Decompression speed |
-|-----------|-------------------|-------------------|---------------------|
-| None | 0.99 | 504 MB/s | 686 MB/s |
-| lzo | 1.66 | 398 MB/s | 442 MB/s |
-| zlib | 2.58 | 65 MB/s | 241 MB/s |
-| zstd 1 | 2.57 | 260 MB/s | 383 MB/s |
-| zstd 3 | 2.71 | 174 MB/s | 408 MB/s |
-| zstd 6 | 2.87 | 70 MB/s | 398 MB/s |
-| zstd 9 | 2.92 | 43 MB/s | 406 MB/s |
-| zstd 12 | 2.93 | 21 MB/s | 408 MB/s |
-| zstd 15 | 3.01 | 11 MB/s | 354 MB/s |
-
-
-## SquashFS
-
-* The patch is located in `squashfs.diff`
-* Additionally `fs/squashfs/zstd_wrapper.c` is provided as a source for convenience.
-* The patch has been tested on the master branch of the kernel.
-
-### Benchmarks
-
-Benchmarks run on a Ubuntu 14.04 with 2 cores and 4 GiB of RAM.
-The VM is running on a Macbook Pro with a 3.1 GHz Intel Core i7 processor,
-16 GB of ram, and a SSD.
-The kernel running was built from the master branch with the patch.
-
-The compression benchmark is the file tree from the SquashFS archive found in the
-Ubuntu 16.10 desktop image (ubuntu-16.10-desktop-amd64.iso).
-The compression benchmark uses mksquashfs with the default block size (128 KB)
-and various compression algorithms/compression levels.
-`xz` and `zstd` are also benchmarked with 256 KB blocks.
-The decompression benchmark is timing how long it takes to `tar` the file tree
-into `/dev/null`.
-See `squashfs-benchmark.sh` for details.
-
-| Algorithm | Compression ratio | Compression speed | Decompression speed |
-|----------------|-------------------|-------------------|---------------------|
-| gzip | 2.92 | 15 MB/s | 128 MB/s |
-| lzo | 2.64 | 9.5 MB/s | 217 MB/s |
-| lz4 | 2.12 | 94 MB/s | 218 MB/s |
-| xz | 3.43 | 5.5 MB/s | 35 MB/s |
-| xz 256 KB | 3.53 | 5.4 MB/s | 40 MB/s |
-| zstd 1 | 2.71 | 96 MB/s | 210 MB/s |
-| zstd 5 | 2.93 | 69 MB/s | 198 MB/s |
-| zstd 10 | 3.01 | 41 MB/s | 225 MB/s |
-| zstd 15 | 3.13 | 11.4 MB/s | 224 MB/s |
-| zstd 16 256 KB | 3.24 | 8.1 MB/s | 210 MB/s |
+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.
projects / thirdparty / zstd.git / commitdiff
