zsmalloc: move it under mm

This patch moves zsmalloc under mm directory.

Before that, description will explain why we have needed custom
allocator.

Zsmalloc is a new slab-based memory allocator for storing compressed
pages.  It is designed for low fragmentation and high allocation success
rate on large object, but <= PAGE_SIZE allocations.

zsmalloc differs from the kernel slab allocator in two primary ways to
achieve these design goals.

zsmalloc never requires high order page allocations to back slabs, or
"size classes" in zsmalloc terms.  Instead it allows multiple
single-order pages to be stitched together into a "zspage" which backs
the slab.  This allows for higher allocation success rate under memory
pressure.

Also, zsmalloc allows objects to span page boundaries within the zspage.
This allows for lower fragmentation than could be had with the kernel
slab allocator for objects between PAGE_SIZE/2 and PAGE_SIZE.  With the
kernel slab allocator, if a page compresses to 60% of it original size,
the memory savings gained through compression is lost in fragmentation
because another object of the same size can't be stored in the leftover
space.

This ability to span pages results in zsmalloc allocations not being
directly addressable by the user.  The user is given an
non-dereferencable handle in response to an allocation request.  That
handle must be mapped, using zs_map_object(), which returns a pointer to
the mapped region that can be used.  The mapping is necessary since the
object data may reside in two different noncontigious pages.

The zsmalloc fulfills the allocation needs for zram perfectly

Bug 200034063

[sjenning@linux.vnet.ibm.com: borrow Seth's quote]
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Bob Liu <bob.liu@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit bcf1647d0899666f0fb90d176abf63bae22abb7c)
Change-Id: I5817d822fc5d81404c4b1310919bdeff2f4cde54
Signed-off-by: Sri Krishna chowdary <schowdary@nvidia.com>

diff --git a/drivers/staging/Kconfig b/drivers/staging/Kconfig
index cfb11200ef90b28823b54051ac6f91b7c941cb3f..6bdbcf6e6f0c3064c78b0ddf1a440fe1812e8f8f 100644 (file)
--- a/drivers/staging/Kconfig
+++ b/drivers/staging/Kconfig
@@ -72,8 +72,6 @@ source "drivers/staging/sep/Kconfig"
 
 source "drivers/staging/iio/Kconfig"
 
-source "drivers/staging/zsmalloc/Kconfig"
-
 source "drivers/staging/zram/Kconfig"
 
 source "drivers/staging/wlags49_h2/Kconfig"

diff --git a/drivers/staging/Makefile b/drivers/staging/Makefile
index e213eec10d2759181cca90cde7b8423338b979e4..5f635699cafb5ee21694b69657d0026da01ccefb 100644 (file)
--- a/drivers/staging/Makefile
+++ b/drivers/staging/Makefile
@@ -32,7 +32,6 @@ obj-$(CONFIG_VME_BUS)         += vme/
 obj-$(CONFIG_DX_SEP)            += sep/
 obj-$(CONFIG_IIO)              += iio/
 obj-$(CONFIG_ZRAM)             += zram/
-obj-$(CONFIG_ZSMALLOC)         += zsmalloc/
 obj-$(CONFIG_WLAGS49_H2)       += wlags49_h2/
 obj-$(CONFIG_WLAGS49_H25)      += wlags49_h25/
 obj-$(CONFIG_FB_SM7XX)         += sm7xxfb/

diff --git a/drivers/staging/zram/zram_drv.h b/drivers/staging/zram/zram_drv.h
index 97a3acf6ab7613ebf4cee59710511162a9719fa0..d8f6596513c3c7b8a853d66fc9746f3607fe0352 100644 (file)
--- a/drivers/staging/zram/zram_drv.h
+++ b/drivers/staging/zram/zram_drv.h
@@ -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

diff --git a/drivers/staging/zsmalloc/Kconfig b/drivers/staging/zsmalloc/Kconfig
deleted file mode 100644 (file)
index 7fab032..0000000
--- a/drivers/staging/zsmalloc/Kconfig
+++ /dev/null
@@ -1,10 +0,0 @@
-config ZSMALLOC
-       bool "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.

diff --git a/drivers/staging/zsmalloc/Makefile b/drivers/staging/zsmalloc/Makefile
deleted file mode 100644 (file)
index b134848..0000000
--- a/drivers/staging/zsmalloc/Makefile
+++ /dev/null
@@ -1,3 +0,0 @@
-zsmalloc-y             := zsmalloc-main.o
-
-obj-$(CONFIG_ZSMALLOC) += zsmalloc.o

diff --git a/drivers/staging/zsmalloc/zsmalloc.h b/include/linux/zsmalloc.h
similarity index 100%
rename from drivers/staging/zsmalloc/zsmalloc.h
rename to include/linux/zsmalloc.h

diff --git a/mm/Kconfig b/mm/Kconfig
index ee2e00031ebf2695776b6286f63b72a08697ac72..e85fb9ea4fe11154e3ae9db2a90a6790a725b297 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -478,3 +478,28 @@ config FRONTSWAP
          and swap data is stored as normal on the matching swap device.
 
          If unsure, say Y to enable frontswap.
+
+config ZSMALLOC
+       bool "Memory allocator for compressed pages"
+       depends on MMU
+       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.
+
+config PGTABLE_MAPPING
+       bool "Use page table mapping to access object in zsmalloc"
+       depends on ZSMALLOC
+       help
+         By default, zsmalloc uses a copy-based object mapping method to
+         access allocations that span two pages. However, if a particular
+         architecture (ex, ARM) performs VM mapping faster than copying,
+         then you should select this. This causes zsmalloc to use page table
+         mapping rather than copying for object mapping.
+
+         You can check speed with zsmalloc benchmark[1].
+         [1] https://github.com/spartacus06/zsmalloc

diff --git a/mm/Makefile b/mm/Makefile
index 72c5acb9345fddc928cafdeb8c0a0bad3279f6b4..b5ae0b0cc26c4b1975989a80c91694cd6c1d946e 100644 (file)
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -58,3 +58,4 @@ obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
 obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o
 obj-$(CONFIG_CLEANCACHE) += cleancache.o
 obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
+obj-$(CONFIG_ZSMALLOC) += zsmalloc.o

diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/mm/zsmalloc.c
similarity index 99%
rename from drivers/staging/zsmalloc/zsmalloc-main.c
rename to mm/zsmalloc.c
index 288f58252a18659baf0912be92270caf850f8007..6ad98bb06411ba17626047c00311b3660bca0ff8 100644 (file)
--- a/drivers/staging/zsmalloc/zsmalloc-main.c
+++ b/mm/zsmalloc.c
@@ -78,8 +78,7 @@
 #include <linux/hardirq.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
-
-#include "zsmalloc.h"
+#include <linux/zsmalloc.h>
 
 /*
  * This must be power of 2 and greater than of equal to sizeof(link_free).