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>

arch/sparc/Kconfig

@@ -26,6 +26,7 @@ config SPARC
 	select RTC_CLASS
 	select RTC_DRV_M48T59
 	select HAVE_PERF_EVENTS
+	select PERF_USE_VMALLOC
 	select HAVE_DMA_ATTRS
 	select HAVE_DMA_API_DEBUG
 
@@ -48,6 +49,7 @@ config SPARC64
 	select RTC_DRV_SUN4V
 	select RTC_DRV_STARFIRE
 	select HAVE_PERF_EVENTS
+	select PERF_USE_VMALLOC
 
 config ARCH_DEFCONFIG
 	string

include/linux/perf_event.h

@@ -442,6 +442,7 @@ enum perf_callchain_context {
 #include <linux/hrtimer.h>
 #include <linux/fs.h>
 #include <linux/pid_namespace.h>
+#include <linux/workqueue.h>
 #include <asm/atomic.h>
 
 #define PERF_MAX_STACK_DEPTH		255
@@ -513,6 +514,10 @@ struct file;
 
 struct perf_mmap_data {
 	struct rcu_head			rcu_head;
+#ifdef CONFIG_PERF_USE_VMALLOC
+	struct work_struct		work;
+#endif
+	int				data_order;
 	int				nr_pages;	/* nr of data pages  */
 	int				writable;	/* are we writable   */
 	int				nr_locked;	/* nr pages mlocked  */

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