powerpc/44x: Support 16K/64K base page sizes on 44x
This adds support for 16k and 64k page sizes on PowerPC 44x processors.
The PGDIR table is much smaller than a page when using 16k or 64k
pages (512 and 32 bytes respectively) so we allocate the PGDIR with
kzalloc() instead of __get_free_pages().
One PTE table covers rather a large memory area when using 16k or 64k
pages (32MB or 512MB respectively), so we can easily put FIXMAP and
PKMAP in the area covered by one PTE table.
Signed-off-by: Yuri Tikhonov <yur@emcraft.com>
Signed-off-by: Vladimir Panfilov <pvr@emcraft.com>
Signed-off-by: Ilya Yanok <yanok@emcraft.com>
Acked-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index f7f5448..1af2257 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -405,23 +405,53 @@
depends on PPC64
default n
-config PPC_64K_PAGES
- bool "64k page size"
- depends on PPC64
- select PPC_HAS_HASH_64K
+choice
+ prompt "Page size"
+ default PPC_4K_PAGES
help
- This option changes the kernel logical page size to 64k. On machines
- without processor support for 64k pages, the kernel will simulate
- them by loading each individual 4k page on demand transparently,
- while on hardware with such support, it will be used to map
- normal application pages.
+ Select the kernel logical page size. Increasing the page size
+ will reduce software overhead at each page boundary, allow
+ hardware prefetch mechanisms to be more effective, and allow
+ larger dma transfers increasing IO efficiency and reducing
+ overhead. However the utilization of memory will increase.
+ For example, each cached file will using a multiple of the
+ page size to hold its contents and the difference between the
+ end of file and the end of page is wasted.
+
+ Some dedicated systems, such as software raid serving with
+ accelerated calculations, have shown significant increases.
+
+ If you configure a 64 bit kernel for 64k pages but the
+ processor does not support them, then the kernel will simulate
+ them with 4k pages, loading them on demand, but with the
+ reduced software overhead and larger internal fragmentation.
+ For the 32 bit kernel, a large page option will not be offered
+ unless it is supported by the configured processor.
+
+ If unsure, choose 4K_PAGES.
+
+config PPC_4K_PAGES
+ bool "4k page size"
+
+config PPC_16K_PAGES
+ bool "16k page size" if 44x
+
+config PPC_64K_PAGES
+ bool "64k page size" if 44x || PPC_STD_MMU_64
+ select PPC_HAS_HASH_64K if PPC_STD_MMU_64
+
+endchoice
config FORCE_MAX_ZONEORDER
int "Maximum zone order"
- range 9 64 if PPC_64K_PAGES
- default "9" if PPC_64K_PAGES
- range 13 64 if PPC64 && !PPC_64K_PAGES
- default "13" if PPC64 && !PPC_64K_PAGES
+ range 9 64 if PPC_STD_MMU_64 && PPC_64K_PAGES
+ default "9" if PPC_STD_MMU_64 && PPC_64K_PAGES
+ range 13 64 if PPC_STD_MMU_64 && !PPC_64K_PAGES
+ default "13" if PPC_STD_MMU_64 && !PPC_64K_PAGES
+ range 9 64 if PPC_STD_MMU_32 && PPC_16K_PAGES
+ default "9" if PPC_STD_MMU_32 && PPC_16K_PAGES
+ range 7 64 if PPC_STD_MMU_32 && PPC_64K_PAGES
+ default "7" if PPC_STD_MMU_32 && PPC_64K_PAGES
range 11 64
default "11"
help
@@ -441,7 +471,7 @@
config PPC_SUBPAGE_PROT
bool "Support setting protections for 4k subpages"
- depends on PPC_64K_PAGES
+ depends on PPC_STD_MMU_64 && PPC_64K_PAGES
help
This option adds support for a system call to allow user programs
to set access permissions (read/write, readonly, or no access)