Add BtrFS benchmarks

contrib/linux-kernel/README.md

@@ -24,3 +24,29 @@ The patches are based off of the linux kernel master branch (version 4.10).
 * 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 athat are expected.
   It can 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 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            |

contrib/linux-kernel/btrfs-benchmark.sh

@@ -0,0 +1,104 @@
+# !/bin/sh
+set -e
+
+# Benchmarks run 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 and
+# 16 GB of RAM and an SSD.
+
+# silesia is a directory that can be downloaded from
+# http://mattmahoney.net/dc/silesia.html
+# ls -l silesia/
+# total 203M
+# -rwxr-xr-x 1 terrelln 9.8M Apr 12  2002 dickens
+# -rwxr-xr-x 1 terrelln  49M May 31  2002 mozilla
+# -rwxr-xr-x 1 terrelln 9.6M Mar 20  2003 mr
+# -rwxr-xr-x 1 terrelln  32M Apr  2  2002 nci
+# -rwxr-xr-x 1 terrelln 5.9M Jul  4  2002 ooffice
+# -rwxr-xr-x 1 terrelln 9.7M Apr 11  2002 osdb
+# -rwxr-xr-x 1 terrelln 6.4M Apr  2  2002 reymont
+# -rwxr-xr-x 1 terrelln  21M Mar 25  2002 samba
+# -rwxr-xr-x 1 terrelln 7.0M Mar 24  2002 sao
+# -rwxr-xr-x 1 terrelln  40M Mar 25  2002 webster
+# -rwxr-xr-x 1 terrelln 8.1M Apr  4  2002 x-ray
+# -rwxr-xr-x 1 terrelln 5.1M Nov 30  2000 xml
+
+# $HOME is on a ext4 filesystem
+BENCHMARK_DIR="$HOME/silesia/"
+N=10
+
+# Normalize the environment
+sudo umount /mnt/btrfs 2> /dev/null > /dev/null || true
+sudo mount -t btrfs $@ /dev/sda3 /mnt/btrfs
+sudo rm -rf /mnt/btrfs/*
+sync
+sudo umount /mnt/btrfs
+sudo mount -t btrfs $@ /dev/sda3 /mnt/btrfs
+
+# Run the benchmark
+echo "Compression"
+time sh -c "for i in \$(seq $N); do sudo cp -r $BENCHMARK_DIR /mnt/btrfs/\$i; done; sync"
+
+echo "Approximate compression ratio"
+printf "%d / %d\n"                                                             \
+  $(df /mnt/btrfs --output=used -B 1 | tail -n 1)                              \
+  $(sudo du /mnt/btrfs -b -d 0 | tr '\t' '\n' | head -n 1);
+
+# Unmount and remount to avoid any caching
+sudo umount /mnt/btrfs
+sudo mount -t btrfs $@ /dev/sda3 /mnt/btrfs
+
+echo "Decompression"
+time sudo tar -c /mnt/btrfs 2> /dev/null | wc -c > /dev/null
+
+sudo rm -rf /mnt/btrfs/*
+sudo umount /mnt/btrfs
+
+# Run for each of -o compress-force={none, lzo, zlib, zstd} 5 times and take the
+# min time and ratio.
+# Ran zstd with compression levels {1, 3, 6, 9, 12, 15}.
+# Original size: 2119415342 B (using du /mnt/btrfs)
+
+# none
+# compress: 4.205 s
+# decompress: 3.090 s
+# ratio: 0.99
+
+# lzo
+# compress: 5.328 s
+# decompress: 4.793 s
+# ratio: 1.66
+
+# zlib
+# compress: 32.588 s
+# decompress: 8.791 s
+# ratio : 2.58
+
+# zstd 1
+# compress: 8.147 s
+# decompress: 5.527 s
+# ratio : 2.57
+
+# zstd 3
+# compress: 12.207 s
+# decompress: 5.195 s
+# ratio : 2.71
+
+# zstd 6
+# compress: 30.253 s
+# decompress: 5.324 s
+# ratio : 2.87
+
+# zstd 9
+# compress: 49.659 s
+# decompress: 5.220 s
+# ratio : 2.92
+
+# zstd 12
+# compress: 99.245 s
+# decompress: 5.193 s
+# ratio : 2.93
+
+# zstd 15
+# compress: 196.997 s
+# decompress: 5.992 s
+# ratio : 3.01