Message-Id: <1353368113-1971-1-git-send-email-minchan@kernel.org>
Date:	Tue, 20 Nov 2012 08:35:10 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Nitin Gupta <ngupta@...are.org>,
	Seth Jennings <sjenning@...ux.vnet.ibm.com>,
	Konrad Rzeszutek Wilk <konrad@...nok.org>,
	Jens Axboe <axboe@...nel.dk>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Luigi Semenzato <semenzato@...gle.com>,
	gaowanlong@...fujitsu.com, Minchan Kim <minchan@...nel.org>
Subject: [PATCH v5 0/3] zram/zsmalloc promotion

This patchset promotes zram/zsmalloc from staging.
Both are very clean and zram have been used by many embedded product
for a long time. For example,major TV companys have used zram as swap
since two years ago and recently our production team released android
smart phone with zram which is used as swap, too. And there is trial
to use zram as swap in ChromeOS project, too. (Although they report
some problem recently, it was not a problem of zram). When you google
zram, you can find various usecase in xda-developers.

The benefit of zram is very clear. With my experience, the benefit
in real practice was to remove jitter of video application.
It would be effect of efficient memory usage by compression but more
issue is whether swap is there or not in the system. As you know,
recent mobile platform have used JAVA so there are lots of anonymous pages.
But embedded system normally doesn't use eMMC or SDCard as swap because
there is wear-leveling issue and latency so we can't reclaim anymous pages.
It sometime ends up making system very slow when it requires to get
contiguous memory and even many file-backed pages are evicted. It's
never what embedded people want it. Zram is one of best solution for that.

Quote from Luigi
"
Since Chrome OS was mentioned: the main reason why we don't use swap
to a disk (rotating or SSD) is because it doesn't degrade gracefully
and leads to a bad interactive experience.  Generally we prefer to
manage RAM at a higher level, by transparently killing and restarting
processes.  But we noticed that zram is fast enough to be competitive
with the latter, and it lets us make more efficient use of the
available RAM.
"

It's time to go out of staging.

Greg, Jens is already OK that zram is located under driver/blocks/.
The issue remained is where we put zsmalloc. The candidate is two
under mm/ or under lib/. Konrad and Nitin wanted to put zsmalloc
into lib/ instead of mm/.

Quote from Nitin
"
I think mm/ directory should only contain the code which is intended
for global use such as the slab allocator, page reclaim code etc.
zsmalloc is used by only one (or possibly two) drivers, so lib/ seems
to be the right place.
"

Quote from Konrand
"
I like the idea of keeping it in /lib or /mm. Actually 'lib' sounds more
appropriate since it is dealing with storing a bunch of pages in a nice
layout for great density purposes.
"

In fact, there is some history about that.

Why I put zsmalloc into under mm firstly was that Andrew had a concern
about using strut page's some fields freely in zsmalloc so he wanted
to maintain it in mm/ if I remember correctly.

So I and Nitin tried to ask the opinion to akpm several times
(at least 6 and even I sent such patch a few month ago) but didn't get
any reply from him or any mm guys so I guess mm guys doesn't have any
concern about that any more.

In point of view that it's an another slab-like allocator,
it might be proper under mm but it's not popular as current mm's
allocators(/SLUB/SLOB and page allocator).

Frankly speaking, I don't care whether we put it to mm/ or lib/.
It seems contributors(ex, Nitin, Konrad, Pekka, Seth and Dan) like lib/
and other mm guys are still silent. That's why I am biased into lib/ now.

If someone yell we should keep it to mm/ by logical claim, I can change
my mind easily. Please raise your hand.

If Andrew doesn't have a concern about that any more, I would like to
locate it into /lib.

This patchset is based on next-20121115.

Minchan Kim (3):
  zsmalloc: promote to lib/
  zram: promote zram from staging
  zram: select ZSMALLOC when ZRAM is configured

 drivers/block/Kconfig                    |    1 +
 drivers/block/Makefile                   |    1 +
 drivers/block/zram/Kconfig               |   26 +
 drivers/block/zram/Makefile              |    3 +
 drivers/block/zram/zram.txt              |   76 +++
 drivers/block/zram/zram_drv.c            |  776 ++++++++++++++++++++++
 drivers/block/zram/zram_drv.h            |  119 ++++
 drivers/block/zram/zram_sysfs.c          |  225 +++++++
 drivers/staging/Kconfig                  |    4 -
 drivers/staging/Makefile                 |    2 -
 drivers/staging/zcache/zcache-main.c     |    4 +-
 drivers/staging/zram/Kconfig             |   25 -
 drivers/staging/zram/Makefile            |    3 -
 drivers/staging/zram/zram.txt            |   76 ---
 drivers/staging/zram/zram_drv.c          |  776 ----------------------
 drivers/staging/zram/zram_drv.h          |  120 ----
 drivers/staging/zram/zram_sysfs.c        |  225 -------
 drivers/staging/zsmalloc/Kconfig         |   10 -
 drivers/staging/zsmalloc/Makefile        |    3 -
 drivers/staging/zsmalloc/zsmalloc-main.c | 1064 ------------------------------
 drivers/staging/zsmalloc/zsmalloc.h      |   43 --
 include/linux/zsmalloc.h                 |   43 ++
 lib/Kconfig                              |   18 +
 lib/Makefile                             |    1 +
 lib/zsmalloc.c                           | 1064 ++++++++++++++++++++++++++++++
 25 files changed, 2355 insertions(+), 2353 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/zram_drv.h
 create mode 100644 drivers/block/zram/zram_sysfs.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/zram/zram_sysfs.c
 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/zsmalloc.h
 create mode 100644 lib/zsmalloc.c

-- 
1.7.9.5

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