Commit 5c1aab1d authored by Nick Terrell's avatar Nick Terrell Committed by Chris Mason
Browse files

btrfs: Add zstd support 

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 |

The next benchmark first copies `linux-4.11.6.tar` [4] to btrfs. Then it
measures the compression ratio, extracts the tar, and deletes the tar.
Then it measures the compression ratio again, and `tar`s the extracted
files into `/dev/null`. See the benchmark file [2] for details.

| Method | Tar Ratio | Extract Ratio | Copy (s) | Extract (s)| Read (s) |
|--------|-----------|---------------|----------|------------|----------|
| None   |      0.97 |          0.78 |    0.981 |      5.501 |    8.807 |
| lzo    |      2.06 |          1.38 |    1.631 |      8.458 |    8.585 |
| zlib   |      3.40 |          1.86 |    7.750 |     21.544 |   11.744 |
| zstd 1 |      3.57 |          1.85 |    2.579 |     11.479 |    9.389 |

[1] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/btrfs-benchmark.sh
[2] https://github.com/facebook/zstd/blob/dev/contrib/linux-kernel/btrfs-extract-benchmark.sh
[3] http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia
[4] https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.11.6.tar.xz

zstd source repository: https://github.com/facebook/zstd



Signed-off-by: default avatarNick Terrell <terrelln@fb.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent 73f3d1b4

fs/btrfs/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -6,6 +6,8 @@ config BTRFS_FS 
	select ZLIB_DEFLATE

	select LZO_COMPRESS

	select LZO_DECOMPRESS

	select ZSTD_COMPRESS

	select ZSTD_DECOMPRESS

	select RAID6_PQ

	select XOR_BLOCKS

	select SRCU

fs/btrfs/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -6,7 +6,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \ 
	   transaction.o inode.o file.o tree-defrag.o \

	   extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \

	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \

	   export.o tree-log.o free-space-cache.o zlib.o lzo.o \

	   export.o tree-log.o free-space-cache.o zlib.o lzo.o zstd.o \

	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \

	   reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \

	   uuid-tree.o props.o hash.o free-space-tree.o

fs/btrfs/compression.c

+1 −0
Original line number Diff line number Diff line
@@ -704,6 +704,7 @@ static struct { 
static const struct btrfs_compress_op * const btrfs_compress_op[] = {

	&btrfs_zlib_compress,

	&btrfs_lzo_compress,

	&btrfs_zstd_compress,

};



void __init btrfs_init_compress(void)

fs/btrfs/compression.h

+4 −2
Original line number Diff line number Diff line
@@ -99,8 +99,9 @@ enum btrfs_compression_type { 
	BTRFS_COMPRESS_NONE  = 0,

	BTRFS_COMPRESS_ZLIB  = 1,

	BTRFS_COMPRESS_LZO   = 2,

	BTRFS_COMPRESS_TYPES = 2,

	BTRFS_COMPRESS_LAST  = 3,

	BTRFS_COMPRESS_ZSTD  = 3,

	BTRFS_COMPRESS_TYPES = 3,

	BTRFS_COMPRESS_LAST  = 4,

};



struct btrfs_compress_op {
@@ -128,5 +129,6 @@ struct btrfs_compress_op { 


extern const struct btrfs_compress_op btrfs_zlib_compress;

extern const struct btrfs_compress_op btrfs_lzo_compress;

extern const struct btrfs_compress_op btrfs_zstd_compress;



#endif

fs/btrfs/ctree.h

+1 −0
Original line number Diff line number Diff line
@@ -270,6 +270,7 @@ struct btrfs_super_block { 
	 BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS |		\

	 BTRFS_FEATURE_INCOMPAT_BIG_METADATA |		\

	 BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO |		\

	 BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD |		\

	 BTRFS_FEATURE_INCOMPAT_RAID56 |		\

	 BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF |		\

	 BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA |	\

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