gem_tiled_swapping: Limit to available memory

If there is not enough free RAM+swap for us to execute our test, we will
hit OOM, so check first.

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. */
+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

@@ -85,6 +85,40 @@ intel_get_total_ram_mb(void)
 	return retval / (1024*1024);
 }
 
+/**
+ * intel_get_avail_ram_mb:
+ *
+ * Returns:
+ * The amount of unused system RAM available in MB.
+ */
+uint64_t
+intel_get_avail_ram_mb(void)
+{
+	uint64_t retval;
+
+#ifdef HAVE_STRUCT_SYSINFO_TOTALRAM /* Linux */
+	struct sysinfo sysinf;
+	int ret;
+
+	ret = sysinfo(&sysinf);
+	assert(ret == 0);
+
+	retval = sysinf.freeram;
+	retval *= sysinf.mem_unit;
+#elif defined(_SC_PAGESIZE) && defined(_SC_PHYS_PAGES) /* Solaris */
+	long pagesize, npages;
+
+	pagesize = sysconf(_SC_PAGESIZE);
+        npages = sysconf(_SC_AVPHYS_PAGES);
+
+	retval = (uint64_t) pagesize * npages;
+#else
+#error "Unknown how to get available RAM for this OS"
+#endif
+
+	return retval / (1024*1024);
+}
+
 /**
  * intel_get_total_swap_mb:
  *