uncachedev: mmap memory that is not cached by CPUs2013.1archived-2013.1

This patch creates a new character device, uncachedev.
Pages of RAM allocated by this device are not cached by
CPUs.

Uses for such pages:
1) Determining *very* pessimistic emperical worst-
   case execution times.
2) Compare against performance with caches (quantify
   the avg. case benefit).
3) Deterministic memory accesses (access cannot cause a
   cache eviction.)
4) Theoretically, increased performance can be achieved
   by storing infrequently accessed data in uncache pages.

uncachedev allocates pages with the pgprot_noncached() page
attribute for user applications. Since pages allocated by
uncachedev are not locked in memory by default, applications
with any access level may mmap pages with uncachedev.

Limitations:
1) Uncache pages must be MAP_PRIVATE.
2) Remapping not supported.

Usage (user level):
	int size = NR_PAGES*PAGE_SIZE;
	int fd = open("/dev/litmus/uncache", O_RDWR);
	char *data = mmap(NULL, size, PROT_READ | PROT_WRITE,
					MAP_PRIVATE, fd, 0);
	<...do stuff...>
	munmap(data, size);

1 files changed, 1 insertions, 0 deletions

diff --git a/litmus/Makefile b/litmus/Makefile
index d26ca7076b62..2bddc94a399f 100644
--- a/litmus/Makefile
+++ b/litmus/Makefile
@@ -18,6 +18,7 @@ obj-y     = sched_plugin.o litmus.o \
             bheap.o \
             binheap.o \
             ctrldev.o \
+            uncachedev.o \
             sched_gsn_edf.o \
             sched_psn_edf.o \
             sched_pfp.o