Re: [PATCH v6 0/5] zram/zsmalloc promotion

[Luigi Semenzato <semenzato@google.com>]

During earlier discussions of zswap there was a plan to make it work
with zsmalloc as an option instead of zbud. Does zbud work for
compression factors better than 2:1?  I have the impression (maybe
wrong) that it does not.  In our use of zram (Chrome OS) typical
overall compression ratios are between 2.5:1 and 3:1.  We would hate
to waste that memory if we switch to zswap.

Thanks!


On Tue, Aug 13, 2013 at 10:55 PM, Minchan Kim <minchan@kernel.org> wrote:
> It's 6th trial of zram/zsmalloc promotion.
> [patch 5, zram: promote zram from staging] explains why we need zram.
>
> Main reason to block promotion is there was no review of zsmalloc part
> while Jens already acked zram part.
>
> At that time, zsmalloc was used for zram, zcache and zswap so everybody
> wanted to make it general and at last, Mel reviewed it.
> Most of review was related to zswap dumping mechanism which can pageout
> compressed page into swap in runtime and zswap gives up using zsmalloc
> and invented a new wheel, zbud. Other reviews were not major.
> http://lkml.indiana.edu/hypermail/linux/kernel/1304.1/04334.html
>
> Zcache don't use zsmalloc either so only zsmalloc user is zram now.
> So I think there is no concern any more.
>
> Patch 1 adds new Kconfig for zram to use page table method instead
> of copy. Andrew suggested it.
>
> Patch 2 adds lots of commnt for zsmalloc.
>
> Patch 3 moves zsmalloc under driver/staging/zram because zram is only
> user for zram now.
>
> Patch 4 makes unmap_kernel_range exportable function because zsmalloc
> have used map_vm_area which is already exported function but zsmalloc
> need to use unmap_kernel_range and it should be built with module.
>
> Patch 5 moves zram from driver/staging to driver/blocks, finally.
>
> It touches mm, staging, blocks so I am not sure who is right position
> maintainer so I will Cc Andrw, Jens and Greg.
>
> This patch is based on next-20130813.
>
> Thanks.
>
> Minchan Kim (4):
>   zsmalloc: add Kconfig for enabling page table method
>   zsmalloc: move it under zram
>   mm: export unmap_kernel_range
>   zram: promote zram from staging
>
> Nitin Cupta (1):
>   zsmalloc: add more comment
>
>  drivers/block/Kconfig                    |    2 +
>  drivers/block/Makefile                   |    1 +
>  drivers/block/zram/Kconfig               |   37 +
>  drivers/block/zram/Makefile              |    3 +
>  drivers/block/zram/zram.txt              |   71 ++
>  drivers/block/zram/zram_drv.c            |  987 +++++++++++++++++++++++++++
>  drivers/block/zram/zsmalloc.c            | 1084 ++++++++++++++++++++++++++++++
>  drivers/staging/Kconfig                  |    4 -
>  drivers/staging/Makefile                 |    2 -
>  drivers/staging/zram/Kconfig             |   25 -
>  drivers/staging/zram/Makefile            |    3 -
>  drivers/staging/zram/zram.txt            |   77 ---
>  drivers/staging/zram/zram_drv.c          |  984 ---------------------------
>  drivers/staging/zram/zram_drv.h          |  125 ----
>  drivers/staging/zsmalloc/Kconfig         |   10 -
>  drivers/staging/zsmalloc/Makefile        |    3 -
>  drivers/staging/zsmalloc/zsmalloc-main.c | 1063 -----------------------------
>  drivers/staging/zsmalloc/zsmalloc.h      |   43 --
>  include/linux/zram.h                     |  123 ++++
>  include/linux/zsmalloc.h                 |   52 ++
>  mm/vmalloc.c                             |    1 +
>  21 files changed, 2361 insertions(+), 2339 deletions(-)
>  create mode 100644 drivers/block/zram/Kconfig
>  create mode 100644 drivers/block/zram/Makefile
>  create mode 100644 drivers/block/zram/zram.txt
>  create mode 100644 drivers/block/zram/zram_drv.c
>  create mode 100644 drivers/block/zram/zsmalloc.c
>  delete mode 100644 drivers/staging/zram/Kconfig
>  delete mode 100644 drivers/staging/zram/Makefile
>  delete mode 100644 drivers/staging/zram/zram.txt
>  delete mode 100644 drivers/staging/zram/zram_drv.c
>  delete mode 100644 drivers/staging/zram/zram_drv.h
>  delete mode 100644 drivers/staging/zsmalloc/Kconfig
>  delete mode 100644 drivers/staging/zsmalloc/Makefile
>  delete mode 100644 drivers/staging/zsmalloc/zsmalloc-main.c
>  delete mode 100644 drivers/staging/zsmalloc/zsmalloc.h
>  create mode 100644 include/linux/zram.h
>  create mode 100644 include/linux/zsmalloc.h
>
> --
> 1.7.9.5
>

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