[PATCH 0/3] erofs: some decompression improvements

[Gao Xiang]

Hi folks,

This patchset is mainly intended for the upcoming LZMA preparation,
but they still have some benefits to the exist LZ4 decompression.

The first patch looks up compression algorithms on mapping instead
of in the decompression frontend, which is used for the rest patches.

The second patch introduces another compression HEAD (HEAD2) so that
each file can be compressed with two different algorithms at most,
which can be used for the upcoming LZMA compression and LZ4 range
dictionary compression for various data patterns.

The third patch introduces a new readmore decompression strategy to
avoid partial decompression for large big pcluster. It resolves the
randread issue mentioned in the original big pcluster patchset [1]:

randread
Kernel: 5.15.0-rc2+
pclustersize		Vanilla		Patched
 4096			 54.6 MiB/s	 54.0 MiB/s
16384			117.4 MiB/s	143.8 MiB/s
32768			113.6 MiB/s	199.6 MiB/s
65536			 72.8 MiB/s	236.4 MiB/s

The latest version can also be fetched from
git://git.kernel.org/pub/scm/linux/kernel/git/xiang/linux.git -b erofs/readmore

[1] https://lore.kernel.org/r/20210407043927.10623-1-xiang@xxxxxxxxxx

Thanks,
Gao Xiang

Gao Xiang (3):
  erofs: get compression algorithms directly on mapping
  erofs: introduce the secondary compression head
  erofs: introduce readmore decompression strategy

 fs/erofs/compress.h          |   5 --
 fs/erofs/erofs_fs.h          |   8 ++-
 fs/erofs/internal.h          |  28 ++++++++-
 fs/erofs/zdata.c             | 106 ++++++++++++++++++++++++++---------
 fs/erofs/zmap.c              |  57 ++++++++++++-------
 include/trace/events/erofs.h |   2 +-
 6 files changed, 150 insertions(+), 56 deletions(-)

-- 
2.20.1