| Message ID | 20170724113708.18088-2-nefelim4ag@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, Jul 24, 2017 at 02:37:06PM +0300, Timofey Titovets wrote: > Get small sample from input data > and calculate byte type count for that sample > > Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com> > --- > fs/btrfs/compression.c | 24 ++++++++++++++++++++++-- > fs/btrfs/compression.h | 11 +++++++++++ > 2 files changed, 33 insertions(+), 2 deletions(-) > > diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c > index 63f54bd2d5bb..1501d4fe90cc 100644 > --- a/fs/btrfs/compression.c > +++ b/fs/btrfs/compression.c > @@ -1068,15 +1068,35 @@ 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; > + struct heuristic_bucket_item *bucket; > + int a, b, ret; > + u8 symbol, *input_data; > + > + ret = 1; > + > + bucket = kcalloc(BTRFS_HEURISTIC_BUCKET_SIZE, > + sizeof(struct heuristic_bucket_item), GFP_NOFS); > + > + if (!bucket) > + goto out; > > while (index <= end_index) { > page = find_get_page(inode->i_mapping, index); > - kmap(page); > + input_data = kmap(page); > + a = 0; > + while (a < PAGE_SIZE) { > + for (b = 0; b < BTRFS_HEURISTIC_READ_SIZE; b++) { > + symbol = input_data[a+b]; > + bucket[symbol].count++; > + } > + a += BTRFS_HEURISTIC_ITERATOR_OFFSET; > + } > kunmap(page); > put_page(page); > index++; > } > > +out: > + kfree(bucket); > return ret; > } > diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h > index d1f4eee2d0af..984943e5e1ae 100644 > --- a/fs/btrfs/compression.h > +++ b/fs/btrfs/compression.h > @@ -129,6 +129,17 @@ struct btrfs_compress_op { > extern const struct btrfs_compress_op btrfs_zlib_compress; > extern const struct btrfs_compress_op btrfs_lzo_compress; > > +struct heuristic_bucket_item { > + u8 padding; > + u8 symbol; > + u16 count; > +}; > + > +#define BTRFS_HEURISTIC_READ_SIZE 16 > +#define BTRFS_HEURISTIC_READS_PER_PAGE 8*PAGE_SIZE/4096 I hate magic numbers, why is this 8*PAGE_SIZE/4096? If you want to check every 512 bytes why not just set BTRFS_HEURISTIC_ITERATOR_OFFSET to 512? That makes it easier to understand what you are trying to accomplish. Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c index 63f54bd2d5bb..1501d4fe90cc 100644 --- a/fs/btrfs/compression.c +++ b/fs/btrfs/compression.c @@ -1068,15 +1068,35 @@ 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; + struct heuristic_bucket_item *bucket; + int a, b, ret; + u8 symbol, *input_data; + + ret = 1; + + bucket = kcalloc(BTRFS_HEURISTIC_BUCKET_SIZE, + sizeof(struct heuristic_bucket_item), GFP_NOFS); + + if (!bucket) + goto out; while (index <= end_index) { page = find_get_page(inode->i_mapping, index); - kmap(page); + input_data = kmap(page); + a = 0; + while (a < PAGE_SIZE) { + for (b = 0; b < BTRFS_HEURISTIC_READ_SIZE; b++) { + symbol = input_data[a+b]; + bucket[symbol].count++; + } + a += BTRFS_HEURISTIC_ITERATOR_OFFSET; + } kunmap(page); put_page(page); index++; } +out: + kfree(bucket); return ret; } diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h index d1f4eee2d0af..984943e5e1ae 100644 --- a/fs/btrfs/compression.h +++ b/fs/btrfs/compression.h @@ -129,6 +129,17 @@ struct btrfs_compress_op { extern const struct btrfs_compress_op btrfs_zlib_compress; extern const struct btrfs_compress_op btrfs_lzo_compress; +struct heuristic_bucket_item { + u8 padding; + u8 symbol; + u16 count; +}; + +#define BTRFS_HEURISTIC_READ_SIZE 16 +#define BTRFS_HEURISTIC_READS_PER_PAGE 8*PAGE_SIZE/4096 +#define BTRFS_HEURISTIC_ITERATOR_OFFSET PAGE_SIZE/BTRFS_HEURISTIC_READS_PER_PAGE +#define BTRFS_HEURISTIC_BUCKET_SIZE 256 + int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end); #endif
Get small sample from input data and calculate byte type count for that sample Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com> --- fs/btrfs/compression.c | 24 ++++++++++++++++++++++-- fs/btrfs/compression.h | 11 +++++++++++ 2 files changed, 33 insertions(+), 2 deletions(-)