[PATCH v2 6/8] staging: erofs: introduce LZ4 decompression inplace
yuchao0 at huawei.com
Fri Jun 21 09:50:50 UTC 2019
On 2019/6/21 0:07, Gao Xiang wrote:
> compressed data will be usually loaded into last pages of
> the extent (the last page for 4k) for in-place decompression
> (more specifically, in-place IO), as ilustration below,
> start of compressed logical extent
> | end of this logical extent
> | |
> ... | page 6 | page 7 | page 8 | page 9 | ...
> . ^ . ^
> . |compressed|
> . | data |
> . . .
> |< dstsize >|<margin>|
> oend iend
> op ip
> Therefore, it's possible to do decompression inplace (thus no
> memcpy at all) if the margin is sufficient and safe enough ,
> and it can be implemented only for fixed-size output compression
> compared with fixed-size input compression.
> No memcpy for most of in-place IO (about 99% of enwik9) after
> decompression inplace is implemented and sequential read will
> be improved of course (see the following patches for test results).
>  https://github.com/lz4/lz4/commit/b17f578a919b7e6b078cede2d52be29dd48c8e8c
> Signed-off-by: Gao Xiang <gaoxiang25 at huawei.com>
Reviewed-by: Chao Yu <yuchao0 at huawei.com>
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