Fix free memory calculation.

base/sys_info_unittest.cc

Index: base/sys_info_unittest.cc
diff --git a/base/sys_info_unittest.cc b/base/sys_info_unittest.cc
index c3b85077071a8ead6a263947fc109e374516a761..f5ef3974b640b4c79f9643327c7353c8de2ce167 100644
--- a/base/sys_info_unittest.cc
+++ b/base/sys_info_unittest.cc
@@ -6,6 +6,7 @@
 
 #include "base/environment.h"
 #include "base/files/file_util.h"
+#include "base/process/process_metrics.h"
 #include "base/sys_info.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
@@ -29,6 +30,32 @@ TEST_F(SysInfoTest, AmountOfMem) {
   EXPECT_GE(base::SysInfo::AmountOfVirtualMemory(), 0);
 }
 
+#if defined(OS_LINUX) || defined(OS_ANDROID)
+TEST_F(SysInfoTest, AmountOfAvailablePhysicalMemory) {
+  // Note: info is in _K_bytes.
+  base::SystemMemoryInfoKB info;
+  ASSERT_TRUE(base::GetSystemMemoryInfo(&info));
+  EXPECT_GT(info.free, 0);
+
+  if (info.available != 0) {
+    // If there is MemAvailable from kernel.
+    EXPECT_LT(info.available, info.total);
+    const int64_t amount = base::SysInfo::AmountOfAvailablePhysicalMemory(info);
+    // We aren't actually testing that it's correct, just that it's sane.
+    EXPECT_GT(amount, info.free * 1024);
+    EXPECT_LT(amount, info.available * 1024);
+    // Simulate as if there is no MemAvailable.
+    info.available = 0;

[Michael K. (Yandex Team), 2017/03/09 10:40:56]

The answer on yours:
If we are running on modern kernel/bot with MemAvailable, we check both
variants:
* inside this "if" block - case #1;
* zero out info.available and just after this block - case #2.

+  }
+
+  // There is no MemAvailable. Check the fallback logic.
+  const int64_t amount = base::SysInfo::AmountOfAvailablePhysicalMemory(info);
+  // We aren't actually testing that it's correct, just that it's sane.
+  EXPECT_GT(amount, info.free * 1024);
+  EXPECT_LT(amount, info.total * 1024);
+}
+#endif  // defined(OS_LINUX) || defined(OS_ANDROID)
+
 TEST_F(SysInfoTest, AmountOfFreeDiskSpace) {
   // We aren't actually testing that it's correct, just that it's sane.
   FilePath tmp_path;