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diff --git a/src/zstd/contrib/linux-kernel/README.md b/src/zstd/contrib/linux-kernel/README.md new file mode 100644 index 000000000..86552b8bd --- /dev/null +++ b/src/zstd/contrib/linux-kernel/README.md @@ -0,0 +1,101 @@ +# Linux Kernel Patch + +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. + +## xxHash kernel module + +* 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 | |