Merge branch 'fbdev-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[pandora-kernel.git] / mm / Kconfig

diff --git a/mm/Kconfig b/mm/Kconfig
index e9c0c61..8ca47a5 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -347,3 +347,26 @@ config NEED_PER_CPU_KM
        depends on !SMP
        bool
        default y
+
+config CLEANCACHE
+       bool "Enable cleancache driver to cache clean pages if tmem is present"
+       default n
+       help
+         Cleancache can be thought of as a page-granularity victim cache
+         for clean pages that the kernel's pageframe replacement algorithm
+         (PFRA) would like to keep around, but can't since there isn't enough
+         memory.  So when the PFRA "evicts" a page, it first attempts to use
+         cleancacne code to put the data contained in that page into
+         "transcendent memory", memory that is not directly accessible or
+         addressable by the kernel and is of unknown and possibly
+         time-varying size.  And when a cleancache-enabled
+         filesystem wishes to access a page in a file on disk, it first
+         checks cleancache to see if it already contains it; if it does,
+         the page is copied into the kernel and a disk access is avoided.
+         When a transcendent memory driver is available (such as zcache or
+         Xen transcendent memory), a significant I/O reduction
+         may be achieved.  When none is available, all cleancache calls
+         are reduced to a single pointer-compare-against-NULL resulting
+         in a negligible performance hit.
+
+         If unsure, say Y to enable cleancache