- 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