perf_event: Provide vmalloc() based mmap() backing

Some architectures such as Sparc, ARM and MIPS (basically
everything with flush_dcache_page()) need to deal with dcache
aliases by carefully placing pages in both kernel and user maps.

These architectures typically have to use vmalloc_user() for this.

However, on other architectures, vmalloc() is not needed and has
the downsides of being more restricted and slower than regular
allocations.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: David Miller <davem@davemloft.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1254830228.21044.272.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

init/Kconfig

@@ -921,6 +921,11 @@ config HAVE_PERF_EVENTS
 	help
 	  See tools/perf/design.txt for details.
 
+config PERF_USE_VMALLOC
+	bool
+	help
+	  See tools/perf/design.txt for details
+
 menu "Kernel Performance Events And Counters"
 
 config PERF_EVENTS
@@ -976,6 +981,19 @@ config PERF_COUNTERS
 
 	  Say N if unsure.
 
+config DEBUG_PERF_USE_VMALLOC
+	default n
+	bool "Debug: use vmalloc to back perf mmap() buffers"
+	depends on PERF_EVENTS && DEBUG_KERNEL
+	select PERF_USE_VMALLOC
+	help
+	 Use vmalloc memory to back perf mmap() buffers.
+
+	 Mostly useful for debugging the vmalloc code on platforms
+	 that don't require it.
+
+	 Say N if unsure.
+
 endmenu
 
 config VM_EVENT_COUNTERS