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

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.

>
> 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.

>
> 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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