gem_tiled_swapping: Purge all page/swap caches first

Reset the system to a vanilla state before we query how much RAM/swap
space is available for our testing.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

lib/igt_aux.h

@@ -61,6 +61,7 @@ void igt_wait_for_keypress(void);
 
 /* These are separate to allow easier testing when porting, see the comment at
  * the bottom of intel_os.c. */
+void intel_purge_vm_caches(void);
 uint64_t intel_get_avail_ram_mb(void);
 uint64_t intel_get_total_ram_mb(void);
 uint64_t intel_get_total_swap_mb(void);

lib/intel_os.c

@@ -185,6 +185,19 @@ intel_get_total_swap_mb(void)
 	return retval / (1024*1024);
 }
 
+void
+intel_purge_vm_caches(void)
+{
+	int fd;
+
+	fd = open("/proc/sys/vm/drop_caches", O_RDWR);
+	if (fd < 0)
+		return;
+
+	write(fd, "3\n", 2);
+	close(fd);
+}
+
 
 /*
  * When testing a port to a new platform, create a standalone test binary

tests/gem_tiled_swapping.c

@@ -102,6 +102,7 @@ igt_simple_main
 	current_tiling_mode = I915_TILING_X;
 
 	igt_skip_on_simulation();
+	intel_purge_vm_caches();
 
 	fd = drm_open_any();
 	/* need slightly more than available memory */