Re: [PATCH v3 0/9] zram: introduce crypto decompress noctx API and use it on zram

[Joonsoo Kim <iamjoonsoo.kim@lge.com>]

On Mon, Sep 21, 2015 at 12:58:12PM +0900, Minchan Kim wrote:
> On Fri, Sep 18, 2015 at 02:19:15PM +0900, Joonsoo Kim wrote:
> > This patchset makes zram to use crypto API in order to support
> > more compression algorithm.
> > 
> > The reason we need to support vairous compression algorithms is that
> > zram's performance is highly depend on workload and compression algorithm
> > and architecture. Every compression algorithm has it's own strong point.
> > For example, zlib is the best for compression ratio, but, it's
> > (de)compression speed is rather slow. Against my expectation, in my kernel
> > build test with zram swap, in low-memory condition on x86, zlib shows best
> > performance than others. In this case, I guess that compression ratio is
> > the most important factor. Unlike this situation, on ARM, maybe fast
> > (de)compression speed is the most important because it's computation speed
> > is slower than x86.
> 
> Fair enough. lzo and lz4 cannot cover all of workloads so surely, there are
> workloads other compressor algorithm can win. As well, we could support
> H/W compressor with crypto support so I think crypto is a way to go.

Hello, Minchan.

Good!

> 
> One thing I have a concern is I don't want to bind some of compressor
> algorithm to zram statically. User can see what kinds of crypto compressor
> support in his system via /proc/crypto and use it dynamically.
> I hope zram supports it.

Okay. I will handle it next version.

> > 
> > Anyway, there is a concern from Sergey to use crypto API in zram. Current
> > crypto API has a limitation that always require tfm object to (de)compress
> > something because some of (de)compression function requires scratch buffer
> > embedded on tfm even if some of (de)compression function doesn't
> > require it. Due to above reason, using crypto API rather than calling
> 
> Nice catch from Sergey!
> 
> > compression library directly causes more memory footprint and this is
> > why zram doesn't use crypto API before.
> > 
> > In this patchset, crypto compress noctx API is introduced to reduce memory
> > footprint caused by maintaining multiple tfm and zram uses it. Before
> > noctx API, zram's performace is down-graded if tfm is insufficient. But,
> > after applying noctx API, performace is restored.
> > 
> > This addresses Sergey's concern perfectly and provides possibility to use
> > various compression algorithm in zram.
> > 
> > Following is zram's read performance number.
> > 
> > * iozone -t 4 -R -r 16K -s 60M -I +Z -i 0 -i 1
> > * max_stream is set to 1
> > * Output is in Kbytes/sec
> > 
> > zram-base vs zram-crypto vs zram-crypto-noctx
> > 
> > Read		10411701.88	6426911.62	9423894.38 
> > Re-read		10017386.62	6428218.88	11000063.50 
> 
> Another patch and number we need to merge this patchset is zlib support
> patchset and number you had experiement.

Okay. Will include.

Thanks.

> > 
> > Thanks.
> > 
> > Joonsoo Kim (7):
> >   crypto: introduce decompression API that can be called via sharable
> >     tfm object
> >   crypto/lzo: support decompress_noctx
> >   crypyo/lz4: support decompress_noctx
> >   crypto/lz4hc: support decompress_noctx
> >   crypto/842: support decompress_noctx
> >   zram: use crypto API for compression
> >   zram: use crypto decompress_noctx API
> > 
> > Sergey Senozhatsky (2):
> >   zram: make stream find and release functions static
> >   zram: pass zstrm down to decompression path
> > 
> >  crypto/842.c                   |   9 +++-
> >  crypto/compress.c              |  36 +++++++++++++++
> >  crypto/crypto_null.c           |   3 +-
> >  crypto/deflate.c               |   3 +-
> >  crypto/lz4.c                   |   9 +++-
> >  crypto/lz4hc.c                 |   9 +++-
> >  crypto/lzo.c                   |   9 +++-
> >  drivers/block/zram/Kconfig     |   8 ++--
> >  drivers/block/zram/Makefile    |   4 +-
> >  drivers/block/zram/zcomp.c     | 102 +++++++++++++++++++++++++++++++----------
> >  drivers/block/zram/zcomp.h     |  42 +++++++----------
> >  drivers/block/zram/zcomp_lz4.c |  47 -------------------
> >  drivers/block/zram/zcomp_lz4.h |  17 -------
> >  drivers/block/zram/zcomp_lzo.c |  47 -------------------
> >  drivers/block/zram/zcomp_lzo.h |  17 -------
> >  drivers/block/zram/zram_drv.c  |  32 +++++++++----
> >  include/linux/crypto.h         |  20 ++++++++
> >  17 files changed, 211 insertions(+), 203 deletions(-)
> >  delete mode 100644 drivers/block/zram/zcomp_lz4.c
> >  delete mode 100644 drivers/block/zram/zcomp_lz4.h
> >  delete mode 100644 drivers/block/zram/zcomp_lzo.c
> >  delete mode 100644 drivers/block/zram/zcomp_lzo.h
> > 
> > -- 
> > 1.9.1
> > 
> --
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