Date:	Wed, 16 Apr 2014 15:53:53 +0200
From:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv9 0/7] add compressing abstraction and multi stream support


Hi,

I'm a bit late on this patch series (sorry for that) but why are we not
using Crypto API for compression algorithm selection and multi stream
support?  Compared to the earlier patches for zram like the ones we did
in July 2013 [1] this patch series requires us to:

- implement compression algorithm support for each algorithm separately
  (when using Crypto API all compression algorithms supported by Crypto
  API are supported automatically)

- manually set the number of maximum active compression streams (earlier
  patches using Crypto API needed a lot less code and automatically scaled
  number of compression streams to number of online CPUs)

>From what I see the pros of the current patch series are:

- dynamic selection of the compression algorithm

- ability to limit number of active streams below tha number of online CPUs

However I believe that both above features can be also implemented on top of
the code using Crypto API.  What am I missing?

[1] https://lkml.org/lkml/2013/7/30/365

Best regards,
--
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

On Thursday, March 06, 2014 05:11:37 PM Minchan Kim wrote:
> Hello Sergey,
> 
> Sorry for the late.
> 
> Today, I tested this patch and confirm that it's really good.
> I send result for the record.
> 
> In x86(4core and x2 hyper threading, i7, 2.8GHz), I did parallel 4 dd
> test with 200m file like below
> 
> dd if=./test200m.file of=mnt/file1 bs=512k count=1024 oflag=direct &
> dd if=./test200m.file of=mnt/file2 bs=512k count=1024 oflag=direct &
> dd if=./test200m.file of=mnt/file3 bs=512k count=1024 oflag=direct &
> dd if=./test200m.file of=mnt/file4 bs=512k count=1024 oflag=direct &
> wait all backgroud job
> 
> The result is 
> 
> When 1 max_comp_streams, elapsed time is 36.26s
> When 8 max_comp_streams, elapsed time is 4.09s
> 
> In ARM(4core, ARMv7, 1.5GHz), I did iozone test.
> 
>       1 max_comp_streams,      8 max_comp_streams
> ==Initial  write      ==Initial  write
> records:   10         records:   10
> avg:       141964.05  avg:       239632.54
> std:       3532.11    (2.49%)    std:       43863.53  (18.30%)
> max:       147900.45  max:       319046.62
> min:       135363.73  min:       178929.40
> ==Rewrite  ==Rewrite
> records:   10         records:   10
> avg:       144757.46  avg:       247410.80
> std:       4019.19    (2.78%)    std:       37378.42  (15.11%)
> max:       150757.72  max:       293284.84
> min:       135127.55  min:       188984.27
> ==Read     ==Read
> records:   10         records:   10
> avg:       208325.22  avg:       202894.24
> std:       57072.62   (27.40%)   std:       41099.56  (20.26%)
> max:       293428.96  max:       289581.12
> min:       79445.37   min:       157478.27
> ==Re-read  ==Re-read
> records:   10         records:   10
> avg:       204750.36  avg:       237406.96
> std:       36959.99   (18.05%)   std:       41518.36  (17.49%)
> max:       268399.89  max:       286898.13
> min:       154831.28  min:       160326.88
> ==Reverse  Read       ==Reverse  Read
> records:   10         records:   10
> avg:       215043.10  avg:       208946.35
> std:       31239.60   (14.53%)   std:       38859.74  (18.60%)
> max:       251564.57  max:       284481.31
> min:       154719.20  min:       155024.33
> ==Stride   read       ==Stride   read
> records:   10         records:   10
> avg:       227246.54  avg:       198925.10
> std:       31105.89   (13.69%)   std:       30721.86  (15.44%)
> max:       290020.34  max:       227178.70
> min:       157399.46  min:       153592.91
> ==Random   read       ==Random   read
> records:   10         records:   10
> avg:       238239.81  avg:       216298.41
> std:       37276.91   (15.65%)   std:       38194.73  (17.66%)
> max:       291416.20  max:       286345.37
> min:       152734.23  min:       151871.52
> ==Mixed    workload   ==Mixed    workload
> records:   10         records:   10
> avg:       208434.11  avg:       234355.66
> std:       31385.40   (15.06%)   std:       22064.02  (9.41%)
> max:       253990.11  max:       270412.58
> min:       162041.47  min:       186052.12
> ==Random   write      ==Random   write
> records:   10         records:   10
> avg:       142172.54  avg:       290231.28
> std:       6233.67    (4.38%)    std:       46462.35  (16.01%)
> max:       150652.40  max:       338096.54
> min:       130584.14  min:       183253.25
> ==Pwrite   ==Pwrite
> records:   10         records:   10
> avg:       141247.91  avg:       267085.70
> std:       6756.08    (4.78%)    std:       40019.39  (14.98%)
> max:       150239.13  max:       335512.33
> min:       130456.98  min:       180832.45
> ==Pread    ==Pread
> records:   10         records:   10
> avg:       214990.26  avg:       208730.94
> std:       40701.79   (18.93%)   std:       50797.78  (24.34%)
> max:       287060.54  max:       300675.25
> min:       157642.17  min:       156763.98
> 
> So, all write test both x86 and ARM is really huge win
> and I couldn't find any regression!
> 
> Thanks for nice work.
> 
> For all patchset,
> 
> Acked-by: Minchan Kim <minchan@...nel.org>
> 
> On Fri, Feb 28, 2014 at 08:52:00PM +0300, Sergey Senozhatsky wrote:
> > This patchset introduces zcomp compression backend abstraction
> > adding ability to support compression algorithms other than LZO;
> > support for multi compression streams, making parallel compressions
> > possible; adds support for LZ4 compression algorithm.
> > 
> > v8->v9 (reviewed by Andrew Morton):
> > -- add LZ4 backend (+iozone test vs LZO)
> > -- merge patches 'zram: document max_comp_streams' and 'zram: add multi
> >    stream functionality'
> > -- do not extern backend struct from source file
> > -- use find()/release() naming instead of get()/put()
> > -- minor code, commit messages and code comments `nitpicks'
> > -- removed Acked-by Minchan Kim from first two patches, because I've
> >    changed them a bit.
> > 
> > v7->v8 (reviewed by Minchan Kim):
> > -- merge patches 'add multi stream functionality' and 'enable multi
> >    stream compression support in zram'
> > -- return status code from set_max_streams knob and print message on
> >    error
> > -- do not use atomic type for ->avail_strm
> > -- return back: allocate by default only one stream for multi stream backend
> > -- wake sleeping write in zcomp_strm_multi_put() only if we put stream
> >    to idle list
> > -- minor code `nitpicks'
> > 
> > v6->v7 (reviewed by Minchan Kim):
> > -- enable multi and single stream support out of the box (drop
> >    ZRAM_MULTI_STREAM config option)
> > -- add set_max_stream knob, so we can adjust max number of compression
> >    streams in runtime (for multi stream backend at the moment)
> > -- minor code `nitpicks'
> > 
> > v5->v6 (reviewed by Minchan Kim):
> > -- handle single compression stream case separately, using mutex locking,
> >    to address perfomance regression
> > -- handle multi compression stream using spin lock and wait_event()/wake_up()
> > -- make multi compression stream support configurable (ZRAM_MULTI_STREAM
> >    config option)
> > 
> > v4->v5 (reviewed by Minchan Kim):
> > -- renamed zcomp buffer_lock; removed src len and dst len from
> >    compress() and decompress(); not using term `buffer' and
> >    `workmem' in code and documentation; define compress() and
> >    decompress() functions for LZO backend; not using goto's;
> >    do not put idle zcomp_strm to idle list tail.
> > 
> > v3->v4 (reviewed by Minchan Kim):
> > -- renamed compression backend and working memory structs as requested
> >    by Minchan Kim; fixed several issues noted by Minchan Kim.
> > 
> > Sergey Senozhatsky (7):
> >   zram: introduce compressing backend abstraction
> >   zram: use zcomp compressing backends
> >   zram: factor out single stream compression
> >   zram: add multi stream functionality
> >   zram: add set_max_streams knob
> >   zram: make compression algorithm selection possible
> >   zram: add lz4 algorithm backend
> > 
> >  Documentation/ABI/testing/sysfs-block-zram |  17 +-
> >  Documentation/blockdev/zram.txt            |  45 +++-
> >  drivers/block/zram/Kconfig                 |  10 +
> >  drivers/block/zram/Makefile                |   4 +-
> >  drivers/block/zram/zcomp.c                 | 349 +++++++++++++++++++++++++++++
> >  drivers/block/zram/zcomp.h                 |  68 ++++++
> >  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              | 131 ++++++++---
> >  drivers/block/zram/zram_drv.h              |  11 +-
> >  12 files changed, 715 insertions(+), 48 deletions(-)
> >  create mode 100644 drivers/block/zram/zcomp.c
> >  create mode 100644 drivers/block/zram/zcomp.h
> >  create mode 100644 drivers/block/zram/zcomp_lz4.c
> >  create mode 100644 drivers/block/zram/zcomp_lz4.h
> >  create mode 100644 drivers/block/zram/zcomp_lzo.c
> >  create mode 100644 drivers/block/zram/zcomp_lzo.h

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