Hello Sven,

On Sun, Feb 05, 2017 at 08:09:03PM +0100, Sven Schmidt wrote:

This patchset is for updating the LZ4 compression module to a version based
on LZ4 v1.7.3 allowing to use the fast compression algorithm aka LZ4 fast
which provides an "acceleration" parameter as a tradeoff between
high compression ratio and high compression speed.

We want to use LZ4 fast in order to support compression in lustre
and (mostly, based on that) investigate data reduction techniques in behalf of
storage systems.

Also, it will be useful for other users of LZ4 compression, as with LZ4 fast
it is possible to enable applications to use fast and/or high compression
depending on the usecase.
For instance, ZRAM is offering a LZ4 backend and could benefit from an updated
LZ4 in the kernel.

LZ4 homepage: http://www.lz4.org/
LZ4 source repository: https://github.com/lz4/lz4
Source version: 1.7.3

Benchmark (taken from [1], Core i5-4300U @1.9GHz):
----------------|--------------|----------------|----------
Compressor      | Compression  | Decompression  | Ratio
----------------|--------------|----------------|----------
memcpy          |  4200 MB/s   |  4200 MB/s     | 1.000
LZ4 fast 50     |  1080 MB/s   |  2650 MB/s     | 1.375
LZ4 fast 17     |   680 MB/s   |  2220 MB/s     | 1.607
LZ4 fast 5      |   475 MB/s   |  1920 MB/s     | 1.886
LZ4 default     |   385 MB/s   |  1850 MB/s     | 2.101

[1] http://fastcompression.blogspot.de/2015/04/sampling-or-faster-lz4.html

[PATCH 1/5] lib: Update LZ4 compressor module
[PATCH 2/5] lib/decompress_unlz4: Change module to work with new LZ4 module version
[PATCH 3/5] crypto: Change LZ4 modules to work with new LZ4 module version
[PATCH 4/5] fs/pstore: fs/squashfs: Change usage of LZ4 to work with new LZ4 version
[PATCH 5/5] lib/lz4: Remove back-compat wrappers

Today, I did zram-lz4 performance test with fio in current mmotm and
found it makes regression about 20%.

"lz4-update" means current mmots(git://git.cmpxchg.org/linux-mmots.git) so
applied your 5 patches. (But now sure current mmots has recent uptodate
patches)
"revert" means I reverted your 5 patches in current mmots.

                     revert    lz4-update

      seq-write       1547       1339      86.55%
     rand-write      22775      19381      85.10%
       seq-read       7035       5589      79.45%
      rand-read      78556      68479      87.17%
   mixed-seq(R)       1305       1066      81.69%
   mixed-seq(W)       1205        984      81.66%
  mixed-rand(R)      17421      14993      86.06%
  mixed-rand(W)      17391      14968      86.07%

My fio description file

[global]
bs=4k
ioengine=sync
size=100m
numjobs=1
group_reporting
buffer_compress_percentage=30
scramble_buffers=0
filename=/dev/zram0
loops=10
fsync_on_close=1

[seq-write]
bs=64k
rw=write
stonewall

[rand-write]
rw=randwrite
stonewall

[seq-read]
bs=64k
rw=read
stonewall

[rand-read]
rw=randread
stonewall

[mixed-seq]
bs=64k
rw=rw
stonewall

[mixed-rand]
rw=randrw
stonewall