zram/zsmalloc promotion

PATCH Superseded Minchan Kim 4 participants 10 messages Nov 2, 2012 – Nov 19, 2012 1 message not in the archive

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Memory management Staging Block layer Library code +2 more subsystems

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Minchan Kim

author maintainer

2012-11-02 07:06 UTC #0 lore raw

v4 cover 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.
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, Seth and Dan) like lib/ and 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-20121102.

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

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Minchan Kim

author maintainer

2012-11-02 07:06 UTC #1 lore raw

PATCH v4 1/3 zsmalloc: promote to lib/

This patch promotes the slab-based zsmalloc memory allocator from the staging tree to lib/

zcache/zram depends on this allocator for storing compressed RAM pages in an efficient way under system wide memory pressure where high-order (greater than 0) page allocation are very likely to fail.

For more information on zsmalloc and its internals, read the documentation at the top of the zsmalloc.c file.

Signed-off-by Minchan Kim <[email protected]>

---
 drivers/staging/Kconfig                  |    2 -
 drivers/staging/Makefile                 |    1 -
 drivers/staging/zcache/zcache-main.c     |    4 +-
 drivers/staging/zram/zram_drv.h          |    3 +-
 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 ++++++++++++++++++++++++++++++
 12 files changed, 1129 insertions(+), 1127 deletions(-)
 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

drivers/staging/Kconfig +0 -2

index 231a272..d3f4bed 100644
@@ -76,8 +76,6 @@ source "drivers/staging/zram/Kconfig"
 
 source "drivers/staging/zcache/Kconfig"
 
-source "drivers/staging/zsmalloc/Kconfig"
-
 source "drivers/staging/wlags49_h2/Kconfig"
 
 source "drivers/staging/wlags49_h25/Kconfig"

drivers/staging/Makefile +0 -1

index 2b291c0..ff8133d 100644
@@ -33,7 +33,6 @@ obj-$(CONFIG_DX_SEP)            += sep/
 obj-$(CONFIG_IIO)		+= iio/
 obj-$(CONFIG_ZRAM)		+= zram/
 obj-$(CONFIG_ZCACHE)		+= zcache/
-obj-$(CONFIG_ZSMALLOC)		+= zsmalloc/
 obj-$(CONFIG_WLAGS49_H2)	+= wlags49_h2/
 obj-$(CONFIG_WLAGS49_H25)	+= wlags49_h25/
 obj-$(CONFIG_FB_SM7XX)		+= sm7xxfb/

drivers/staging/zcache/zcache-main.c +2 -2

index 52b43b7..34b2c5c 100644
@@ -32,9 +32,9 @@
 #include <linux/crypto.h>
 #include <linux/string.h>
 #include <linux/idr.h>
-#include "tmem.h"
+#include <linux/zsmalloc.h>
 
-#include "../zsmalloc/zsmalloc.h"
+#include "tmem.h"
 
 #ifdef CONFIG_CLEANCACHE
 #include <linux/cleancache.h>

drivers/staging/zram/zram_drv.h +1 -2

index df2eec4..1e72965 100644
@@ -17,8 +17,7 @@
 
 #include <linux/spinlock.h>
 #include <linux/mutex.h>
-
-#include "../zsmalloc/zsmalloc.h"
+#include <linux/zsmalloc.h>
 
 /*
  * Some arbitrary value. This is just to catch

drivers/staging/zsmalloc/Kconfig deleted +0 ~~-10~~

deleted file mode 100644
index 9084565..0000000
@@ -1,10 +0,0 @@
-config ZSMALLOC
-	tristate "Memory allocator for compressed pages"
-	default n
-	help
-	  zsmalloc is a slab-based memory allocator designed to store
-	  compressed RAM pages.  zsmalloc uses virtual memory mapping
-	  in order to reduce fragmentation.  However, this results in a
-	  non-standard allocator interface where a handle, not a pointer, is
-	  returned by an alloc().  This handle must be mapped in order to
-	  access the allocated space.

drivers/staging/zsmalloc/Makefile deleted +0 -3

deleted file mode 100644
index b134848..0000000
@@ -1,3 +0,0 @@
-zsmalloc-y 		:= zsmalloc-main.o
-
-obj-$(CONFIG_ZSMALLOC)	+= zsmalloc.o

drivers/staging/zsmalloc/zsmalloc-main.c deleted +0 ~~-1064~~

1,064 lines not on this page · raw message

drivers/staging/zsmalloc/zsmalloc.h deleted +0 ~~-43~~

43 lines not on this page · raw message

include/linux/zsmalloc.h new file +43 -0

43 lines not on this page · raw message

lib/Kconfig +18 -0

index 4b31a46..9b1db85 100644
@@ -216,6 +216,24 @@ config DECOMPRESS_LZO
 config GENERIC_ALLOCATOR
 	boolean
 
+config ZSMALLOC
+       tristate "Memory allocator for compressed pages"
+       default n
+       help
+         zsmalloc is a slab-based memory allocator designed to store
+         compressed RAM pages.  zsmalloc uses a memory pool that combines
+         single pages into higher order pages by linking them together
+         using the fields of the struct page. Allocations are then
+         mapped through copy buffers or VM mapping, in order to reduce
+         memory pool fragmentation and increase allocation success rate under
+         memory pressure.
+
+         This results in a non-standard allocator interface where
+         a handle, not a pointer, is returned by the allocation function.
+         This handle must be mapped in order to access the allocated space.
+
+         If unsure, say N.
+
 #
 # reed solomon support is select'ed if needed
 #

lib/Makefile +1 -0

index e91b9df..47438f6 100644
@@ -64,6 +64,7 @@ obj-$(CONFIG_CRC7)	+= crc7.o
 obj-$(CONFIG_LIBCRC32C)	+= libcrc32c.o
 obj-$(CONFIG_CRC8)	+= crc8.o
 obj-$(CONFIG_GENERIC_ALLOCATOR) += genalloc.o
+obj-$(CONFIG_ZSMALLOC) += zsmalloc.o
 
 obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/
 obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/

lib/zsmalloc.c new file +1064 -0

1,064 lines not on this page · raw message

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Pekka Enberg

Acked-by on v4 1/3

2012-11-02 08:22 UTC #2 lore raw

Re: [PATCH v4 1/3] zsmalloc: promote to lib/

Quoted 8 lines · Minchan Kim

This patch promotes the slab-based zsmalloc memory allocator from the staging tree to lib/
zcache/zram depends on this allocator for storing compressed RAM pages in an efficient way under system wide memory pressure where high-order (greater than 0) page allocation are very likely to fail.

Quoted 4 lines

For more information on zsmalloc and its internals, read the documentation at the top of the zsmalloc.c file.
Signed-off-by Minchan Kim <[email protected]>

Acked-by Pekka Enberg <[email protected]>

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Minchan Kim

author maintainer

2012-11-02 07:06 UTC #3 lore raw

PATCH v4 2/3 zram: promote zram from staging

In reply to Minchan Kim

It's time to promote zram from staging because zram lives in staging for a long time and is improved by many contributors so code is very clean. Most important issue, zram's dependency with x86 is solved by making zsmalloc portable. In addition, many embedded product uses zram in real practice so I think there is no reason to prevent promotion now.

Cc Seth Jennings <[email protected]>

Cc Nitin Gupta <[email protected]>

Acked-by Pekka Enberg <[email protected]>

Signed-off-by Minchan Kim <[email protected]>

---
 drivers/block/Kconfig             |    1 +
 drivers/block/Makefile            |    1 +
 drivers/block/zram/Kconfig        |   25 ++
 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           |    2 -
 drivers/staging/Makefile          |    1 -
 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   |  119 ------
 drivers/staging/zram/zram_sysfs.c |  225 -----------
 16 files changed, 1226 insertions(+), 1227 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

drivers/block/Kconfig +1 -0

index 824e09c..f96a93b 100644
@@ -290,6 +290,7 @@ config BLK_DEV_CRYPTOLOOP
 	  cryptoloop device.
 
 source "drivers/block/drbd/Kconfig"
+source "drivers/block/zram/Kconfig"
 
 config BLK_DEV_NBD
 	tristate "Network block device support"

drivers/block/Makefile +1 -0

index 17e82df..7300159 100644
@@ -30,6 +30,7 @@ obj-$(CONFIG_BLK_DEV_UMEM)	+= umem.o
 obj-$(CONFIG_BLK_DEV_NBD)	+= nbd.o
 obj-$(CONFIG_BLK_DEV_CRYPTOLOOP) += cryptoloop.o
 obj-$(CONFIG_VIRTIO_BLK)	+= virtio_blk.o
+obj-$(CONFIG_ZRAM)		+= zram/
 
 obj-$(CONFIG_VIODASD)		+= viodasd.o
 obj-$(CONFIG_BLK_DEV_SX8)	+= sx8.o

drivers/block/zram/Kconfig new file +25 -0

new file mode 100644
index 0000000..be5abe8
@@ -0,0 +1,25 @@
+config ZRAM
+	tristate "Compressed RAM block device support"
+	depends on BLOCK && SYSFS && ZSMALLOC
+	select LZO_COMPRESS
+	select LZO_DECOMPRESS
+	default n
+	help
+	  Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
+	  Pages written to these disks are compressed and stored in memory
+	  itself. These disks allow very fast I/O and compression provides
+	  good amounts of memory savings.
+
+	  It has several use cases, for example: /tmp storage, use as swap
+	  disks and maybe many more.
+
+	  See zram.txt for more information.
+	  Project home: http://compcache.googlecode.com/
+
+config ZRAM_DEBUG
+	bool "Compressed RAM block device debug support"
+	depends on ZRAM
+	default n
+	help
+	  This option adds additional debugging code to the compressed
+	  RAM block device driver.

drivers/block/zram/Makefile new file +3 -0

new file mode 100644
index 0000000..7f4a301
@@ -0,0 +1,3 @@
+zram-y	:=	zram_drv.o zram_sysfs.o
+
+obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/block/zram/zram.txt new file +76 -0

76 lines not on this page · raw message

drivers/block/zram/zram_drv.c new file +776 -0

776 lines not on this page · raw message

drivers/block/zram/zram_drv.h new file +119 -0

119 lines not on this page · raw message

drivers/block/zram/zram_sysfs.c new file +225 -0

225 lines not on this page · raw message

drivers/staging/Kconfig +0 -2

index d3f4bed..3eb5ef7 100644
@@ -72,8 +72,6 @@ source "drivers/staging/sep/Kconfig"
 
 source "drivers/staging/iio/Kconfig"
 
-source "drivers/staging/zram/Kconfig"
-
 source "drivers/staging/zcache/Kconfig"
 
 source "drivers/staging/wlags49_h2/Kconfig"

drivers/staging/Makefile +0 -1

index ff8133d..8ae9f9c 100644
@@ -31,7 +31,6 @@ obj-$(CONFIG_VME_BUS)		+= vme/
 obj-$(CONFIG_IPACK_BUS)		+= ipack/
 obj-$(CONFIG_DX_SEP)            += sep/
 obj-$(CONFIG_IIO)		+= iio/
-obj-$(CONFIG_ZRAM)		+= zram/
 obj-$(CONFIG_ZCACHE)		+= zcache/
 obj-$(CONFIG_WLAGS49_H2)	+= wlags49_h2/
 obj-$(CONFIG_WLAGS49_H25)	+= wlags49_h25/

drivers/staging/zram/Kconfig deleted +0 ~~-25~~

deleted file mode 100644
index be5abe8..0000000
@@ -1,25 +0,0 @@
-config ZRAM
-	tristate "Compressed RAM block device support"
-	depends on BLOCK && SYSFS && ZSMALLOC
-	select LZO_COMPRESS
-	select LZO_DECOMPRESS
-	default n
-	help
-	  Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
-	  Pages written to these disks are compressed and stored in memory
-	  itself. These disks allow very fast I/O and compression provides
-	  good amounts of memory savings.
-
-	  It has several use cases, for example: /tmp storage, use as swap
-	  disks and maybe many more.
-
-	  See zram.txt for more information.
-	  Project home: http://compcache.googlecode.com/
-
-config ZRAM_DEBUG
-	bool "Compressed RAM block device debug support"
-	depends on ZRAM
-	default n
-	help
-	  This option adds additional debugging code to the compressed
-	  RAM block device driver.

drivers/staging/zram/Makefile deleted +0 -3

deleted file mode 100644
index 7f4a301..0000000
@@ -1,3 +0,0 @@
-zram-y	:=	zram_drv.o zram_sysfs.o
-
-obj-$(CONFIG_ZRAM)	+=	zram.o

drivers/staging/zram/zram.txt deleted +0 ~~-76~~

76 lines not on this page · raw message

drivers/staging/zram/zram_drv.c deleted +0 ~~-776~~

776 lines not on this page · raw message

drivers/staging/zram/zram_drv.h deleted +0 ~~-119~~

119 lines not on this page · raw message

drivers/staging/zram/zram_sysfs.c deleted +0 ~~-225~~

225 lines not on this page · raw message

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Minchan Kim

author maintainer

2012-11-02 07:06 UTC #4 lore raw

PATCH v4 3/3 zram: select ZSMALLOC when ZRAM is configured

In reply to Minchan Kim

At the monent, we can configure zram in driver/block once zsmalloc in /lib menu is configured firstly. It's not convenient.

User can configure zram in driver/block regardless of zsmalloc enabling by this patch.

Signed-off-by Minchan Kim <[email protected]>

---
 drivers/block/zram/Kconfig |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

drivers/block/zram/Kconfig +2 -1

index be5abe8..ee23a86 100644
@@ -1,6 +1,7 @@
 config ZRAM
 	tristate "Compressed RAM block device support"
-	depends on BLOCK && SYSFS && ZSMALLOC
+	depends on BLOCK && SYSFS
+	select ZSMALLOC
 	select LZO_COMPRESS
 	select LZO_DECOMPRESS
 	default n

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Pekka Enberg

Acked-by on v4 3/3

2012-11-02 08:23 UTC #5 lore raw

Re: [PATCH v4 3/3] zram: select ZSMALLOC when ZRAM is configured

Quoted 7 lines · Minchan Kim

At the monent, we can configure zram in driver/block once zsmalloc in /lib menu is configured firstly. It's not convenient.
User can configure zram in driver/block regardless of zsmalloc enabling by this patch.
Signed-off-by Minchan Kim <[email protected]>

Acked-by Pekka Enberg <[email protected]>

Andrew Morton

maintainer

2012-11-06 23:32 UTC #6 lore raw

In reply to Minchan Kim

Quoted 1 line · On Fri, 2 Nov 2012 16:12:44 +0900 Minchan Kim <[email protected]> wrote:

This patchset promotes zram/zsmalloc from staging.

The changelogs are distressingly short of *reasons* for doing this!

Quoted 2 lines

Both are very clean and zram have been used by many embedded product for a long time.

Well that's interesting.

Which embedded products? How are they using zram and what benefit are they observing from it, in what scenarios?

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Minchan Kim

author maintainer

2012-11-07 10:38 UTC #8 lore raw

Hi Andrew,

Quoted 7 lines · Andrew Morton

Quoted 1 line · On Fri, 2 Nov 2012 16:12:44 +0900 Minchan Kim <[email protected]> wrote:
This patchset promotes zram/zsmalloc from staging.
The changelogs are distressingly short of *reasons* for doing this!

Quoted 8 lines

Quoted 2 lines
Both are very clean and zram have been used by many embedded product for a long time.
Well that's interesting.
Which embedded products? How are they using zram and what benefit are they observing from it, in what scenarios?

At least, 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.

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.

It's very hard to type with mobile phone. :(

Signature · 2 lines

Kind regards,
Minchan Kim

Luigi Semenzato

2012-11-07 16:40 UTC #9 lore raw

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.

As Minchan said, the zram module in itself appears to work fine. We are hitting other mm issues (one of which was recently fixed) which most likely are exposed by the different patterns of memory allocation when using zram.

Quoted 37 lines · Minchan Kim

Hi Andrew,
Quoted 7 lines · Andrew Morton
Quoted 1 line · On Fri, 2 Nov 2012 16:12:44 +0900 Minchan Kim <[email protected]> wrote:
This patchset promotes zram/zsmalloc from staging.
The changelogs are distressingly short of *reasons* for doing this!
Quoted 8 lines
Quoted 2 lines
Both are very clean and zram have been used by many embedded product for a long time.
Well that's interesting.
Which embedded products? How are they using zram and what benefit are they observing from it, in what scenarios?
At least, 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.
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.

Quoted 5 lines

It's very hard to type with mobile phone. :(
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Kind regards,
Minchan Kim

Minchan Kim

author maintainer

2012-11-19 01:20 UTC #10 lore raw

In reply to Minchan Kim

Andrew?

Quoted 42 lines · Minchan Kim

Hi Andrew,
Quoted 7 lines · Andrew Morton
Quoted 1 line · On Fri, 2 Nov 2012 16:12:44 +0900 Minchan Kim <[email protected]> wrote:
This patchset promotes zram/zsmalloc from staging.
The changelogs are distressingly short of *reasons* for doing this!
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Both are very clean and zram have been used by many embedded product for a long time.
Well that's interesting.
Which embedded products? How are they using zram and what benefit are they observing from it, in what scenarios?
At least, 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.
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.
It's very hard to type with mobile phone. :(
Signature · 2 lines
Kind regards,
Minchan Kim

Signature · 8 lines

Kind regards,
Minchan Kim

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