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Message-ID: <CAA25o9Q1KVHEzdeXJFe9A8K9MULysq_ShWrUBZM4-h=5vmaQ8w@mail.gmail.com>
Date: Wed, 14 Aug 2013 08:53:31 -0700
From: Luigi Semenzato <semenzato@...gle.com>
To: Minchan Kim <minchan@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Jens Axboe <axboe@...nel.dk>,
Seth Jennings <sjenning@...ux.vnet.ibm.com>,
Nitin Gupta <ngupta@...are.org>,
Konrad Rzeszutek Wilk <konrad@...nok.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Pekka Enberg <penberg@...helsinki.fi>,
Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH v6 0/5] zram/zsmalloc promotion
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@...nel.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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