diff options
| -rw-r--r-- | fs/btrfs/compression.c | 33 | ||||
| -rw-r--r-- | fs/btrfs/compression.h | 2 | ||||
| -rw-r--r-- | fs/btrfs/inode.c | 8 |
3 files changed, 39 insertions, 4 deletions
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 3896bd0175ec..883ecc58fd0d 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -1047,3 +1047,36 @@ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start, return 1; } + +/* + * Compression heuristic. + * + * For now is's a naive and optimistic 'return true', we'll extend the logic to + * quickly (compared to direct compression) detect data characteristics + * (compressible/uncompressible) to avoid wasting CPU time on uncompressible + * data. + * + * The following types of analysis can be performed: + * - detect mostly zero data + * - detect data with low "byte set" size (text, etc) + * - detect data with low/high "core byte" set + * + * Return non-zero if the compression should be done, 0 otherwise. + */ +int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) +{ + u64 index = start >> PAGE_SHIFT; + u64 end_index = end >> PAGE_SHIFT; + struct page *page; + int ret = 1; + + while (index <= end_index) { + page = find_get_page(inode->i_mapping, index); + kmap(page); + kunmap(page); + put_page(page); + index++; + } + + return ret; +} diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h index 87f6d3332163..8508ba6b9aef 100644 --- a/fs/btrfs/compression.h +++ b/fs/btrfs/compression.h @@ -129,4 +129,6 @@ struct btrfs_compress_op { extern const struct btrfs_compress_op btrfs_zlib_compress; extern const struct btrfs_compress_op btrfs_lzo_compress; +int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end); + #endif diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 467b9477dac4..0bd008b9e0d1 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -392,7 +392,7 @@ static noinline int add_async_extent(struct async_cow *cow, return 0; } -static inline int inode_need_compress(struct inode *inode) +static inline int inode_need_compress(struct inode *inode, u64 start, u64 end) { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); @@ -405,7 +405,7 @@ static inline int inode_need_compress(struct inode *inode) if (btrfs_test_opt(fs_info, COMPRESS) || BTRFS_I(inode)->flags & BTRFS_INODE_COMPRESS || BTRFS_I(inode)->force_compress) - return 1; + return btrfs_compress_heuristic(inode, start, end); return 0; } @@ -503,7 +503,7 @@ again: * inode has not been flagged as nocompress. This flag can * change at any time if we discover bad compression ratios. */ - if (inode_need_compress(inode)) { + if (inode_need_compress(inode, start, end)) { WARN_ON(pages); pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); if (!pages) { @@ -1576,7 +1576,7 @@ static int run_delalloc_range(void *private_data, struct page *locked_page, } else if (BTRFS_I(inode)->flags & BTRFS_INODE_PREALLOC && !force_cow) { ret = run_delalloc_nocow(inode, locked_page, start, end, page_started, 0, nr_written); - } else if (!inode_need_compress(inode)) { + } else if (!inode_need_compress(inode, start, end)) { ret = cow_file_range(inode, locked_page, start, end, end, page_started, nr_written, 1, NULL); } else { |