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5c1aab1dd5
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: Nick Terrell <terrelln@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
135 lines
4.0 KiB
C
135 lines
4.0 KiB
C
/*
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* Copyright (C) 2008 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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#ifndef __BTRFS_COMPRESSION_
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#define __BTRFS_COMPRESSION_
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/*
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* We want to make sure that amount of RAM required to uncompress an extent is
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* reasonable, so we limit the total size in ram of a compressed extent to
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* 128k. This is a crucial number because it also controls how easily we can
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* spread reads across cpus for decompression.
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*
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* We also want to make sure the amount of IO required to do a random read is
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* reasonably small, so we limit the size of a compressed extent to 128k.
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*/
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/* Maximum length of compressed data stored on disk */
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#define BTRFS_MAX_COMPRESSED (SZ_128K)
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/* Maximum size of data before compression */
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#define BTRFS_MAX_UNCOMPRESSED (SZ_128K)
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struct compressed_bio {
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/* number of bios pending for this compressed extent */
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refcount_t pending_bios;
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/* the pages with the compressed data on them */
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struct page **compressed_pages;
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/* inode that owns this data */
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struct inode *inode;
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/* starting offset in the inode for our pages */
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u64 start;
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/* number of bytes in the inode we're working on */
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unsigned long len;
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/* number of bytes on disk */
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unsigned long compressed_len;
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/* the compression algorithm for this bio */
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int compress_type;
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/* number of compressed pages in the array */
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unsigned long nr_pages;
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/* IO errors */
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int errors;
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int mirror_num;
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/* for reads, this is the bio we are copying the data into */
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struct bio *orig_bio;
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/*
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* the start of a variable length array of checksums only
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* used by reads
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*/
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u32 sums;
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};
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void btrfs_init_compress(void);
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void btrfs_exit_compress(void);
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int btrfs_compress_pages(int type, struct address_space *mapping,
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u64 start, struct page **pages,
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unsigned long *out_pages,
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unsigned long *total_in,
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unsigned long *total_out);
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int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
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unsigned long start_byte, size_t srclen, size_t destlen);
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int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
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unsigned long total_out, u64 disk_start,
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struct bio *bio);
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blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
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unsigned long len, u64 disk_start,
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unsigned long compressed_len,
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struct page **compressed_pages,
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unsigned long nr_pages);
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blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
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int mirror_num, unsigned long bio_flags);
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enum btrfs_compression_type {
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BTRFS_COMPRESS_NONE = 0,
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BTRFS_COMPRESS_ZLIB = 1,
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BTRFS_COMPRESS_LZO = 2,
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BTRFS_COMPRESS_ZSTD = 3,
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BTRFS_COMPRESS_TYPES = 3,
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BTRFS_COMPRESS_LAST = 4,
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};
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struct btrfs_compress_op {
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struct list_head *(*alloc_workspace)(void);
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void (*free_workspace)(struct list_head *workspace);
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int (*compress_pages)(struct list_head *workspace,
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struct address_space *mapping,
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u64 start,
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struct page **pages,
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unsigned long *out_pages,
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unsigned long *total_in,
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unsigned long *total_out);
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int (*decompress_bio)(struct list_head *workspace,
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struct compressed_bio *cb);
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int (*decompress)(struct list_head *workspace,
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unsigned char *data_in,
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struct page *dest_page,
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unsigned long start_byte,
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size_t srclen, size_t destlen);
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};
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extern const struct btrfs_compress_op btrfs_zlib_compress;
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extern const struct btrfs_compress_op btrfs_lzo_compress;
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extern const struct btrfs_compress_op btrfs_zstd_compress;
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#endif
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