[PATCH v5 3/6] Btrfs: implement heuristic sampling logic
From: Timofey Titovets <hidden>
Date: 2017-08-23 00:27:10
Subsystem:
btrfs file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Chris Mason, David Sterba, Alexander Viro, Christian Brauner, Linus Torvalds
Copy sample data from input data range to sample buffer then calculate byte type count for that sample into bucket. Signed-off-by: Timofey Titovets <redacted> --- fs/btrfs/heuristic.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/fs/btrfs/heuristic.c b/fs/btrfs/heuristic.c
index 2c2cadc9dfad..5336638a3b7c 100644
--- a/fs/btrfs/heuristic.c
+++ b/fs/btrfs/heuristic.c@@ -76,20 +76,47 @@ static struct list_head *heuristic_alloc_workspace(void) static int heuristic(struct list_head *ws, struct inode *inode, u64 start, u64 end) { + struct workspace *workspace = list_entry(ws, struct workspace, list); struct page *page; u64 index, index_end; - u8 *input_data; + u8 *in_data; + u32 a, b; + u8 byte; + + /* + * Compression only handle first 128kb of input range + * And just shift over range in loop for compressing it. + * Let's do the same. + */ + if (end - start > BTRFS_MAX_UNCOMPRESSED) + end = start + BTRFS_MAX_UNCOMPRESSED; index = start >> PAGE_SHIFT; index_end = end >> PAGE_SHIFT; + b = 0; for (; index <= index_end; index++) { page = find_get_page(inode->i_mapping, index); - input_data = kmap(page); + in_data = kmap(page); + a = 0; + while (a < PAGE_SIZE-READ_SIZE && b < MAX_SAMPLE_SIZE) { + memcpy(&workspace->sample[b], &in_data[a], READ_SIZE); + a += ITER_SHIFT; + b += READ_SIZE; + } kunmap(page); put_page(page); } + workspace->sample_size = b; + + memset(workspace->bucket, 0, sizeof(*workspace->bucket)*BUCKET_SIZE); + + for (a = 0; a < workspace->sample_size; a++) { + byte = workspace->sample[a]; + workspace->bucket[byte].count++; + } + return 1; } --
2.14.1