On Thu, Jun 29, 2017 at 3:41 PM, Nick Terrell <terrelln@xxxxxx> wrote:
> Add zstd compression and decompression support to BtrFS. zstd at its
> fastest level compresses almost as well as zlib, while offering much
> faster compression and decompression, approaching lzo speeds.
>
> I benchmarked btrfs with zstd compression against no compression, lzo
> compression, and zlib compression. I benchmarked two scenarios. Copying
> a set of files to btrfs, and then reading the files. Copying a tarball
> to btrfs, extracting it to btrfs, and then reading the extracted files.
> After every operation, I call `sync` and include the sync time.
> Between every pair of operations I unmount and remount the filesystem
> to avoid caching. The benchmark files can be found in the upstream
> zstd source repository under
> `contrib/linux-kernel/{btrfs-benchmark.sh,btrfs-extract-benchmark.sh}`
> [1] [2].
>
> I ran the benchmarks on a Ubuntu 14.04 VM 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 first compression benchmark is copying 10 copies of the unzipped
> Silesia corpus [3] into a BtrFS filesystem mounted with
> `-o compress-force=Method`. The decompression benchmark times 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 the benchmark file
> [1] for details. I benchmarked multiple zstd compression levels, although
> the patch uses zstd level 1.
>
> | Method | Ratio | Compression MB/s | Decompression speed |
> |---------|-------|------------------|---------------------|
> | None | 0.99 | 504 | 686 |
> | lzo | 1.66 | 398 | 442 |
> | zlib | 2.58 | 65 | 241 |
> | zstd 1 | 2.57 | 260 | 383 |
> | zstd 3 | 2.71 | 174 | 408 |
> | zstd 6 | 2.87 | 70 | 398 |
> | zstd 9 | 2.92 | 43 | 406 |
> | zstd 12 | 2.93 | 21 | 408 |
> | zstd 15 | 3.01 | 11 | 354 |
>
As a user looking at this graph the zstd 3 seems like the sweet spot to me,
more then twice as fast as zlib with a bit better compression. Is this
going to be
configurable?
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