[memory-infra] Implement PollFastMemoryTotal in ProcessMetricsMemoryDumpProvider.

components/tracing/common/process_metrics_memory_dump_provider_unittest.cc

Index: components/tracing/common/process_metrics_memory_dump_provider_unittest.cc
diff --git a/components/tracing/common/process_metrics_memory_dump_provider_unittest.cc b/components/tracing/common/process_metrics_memory_dump_provider_unittest.cc
index 821f3c22ae49192646662241ada0768fe847efb1..9c1afb8cce88a4cab2da4e67cec032b489ae9675 100644
--- a/components/tracing/common/process_metrics_memory_dump_provider_unittest.cc
+++ b/components/tracing/common/process_metrics_memory_dump_provider_unittest.cc
@@ -12,6 +12,7 @@
 #include "base/trace_event/process_memory_dump.h"
 #include "base/trace_event/process_memory_maps.h"
 #include "base/trace_event/process_memory_totals.h"
+#include "base/trace_event/trace_config_memory_test_util.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -234,4 +235,21 @@ TEST(ProcessMetricsMemoryDumpProviderTest, ParseProcSmaps) {
 }
 #endif  // defined(OS_LINUX) || defined(OS_ANDROID)
 
+TEST(ProcessMetricsMemoryDumpProviderTest, TestPollFastMemoryTotal) {
+  ProcessMetricsMemoryDumpProvider mdp(base::kNullProcessId);
+  mdp.SetFastMemoryPollingEnabled(true);
+  uint64_t value;
+  for (int i = 0; i < 4; i++) {

[Primiano Tucci (use gerrit), 2016/12/13 20:02:39]

I think a slighly better approach would be:
PollFastMemoryTotal(&total1)
kBufSize  = 16 * 1024 * 1024;
auto x = MakeUnique<char[]>(kBufSize);
memset(x.get, 0x42, kFourMB);
PollFastMemoryTotal(&total2);
EXPECT_GT(total2 - total1, kBufSize / 2)

The rationale of the /2 in the test is: gtest in the meantime could do some
frees that make the difference not exactly  16 MB. If you see an increment of at
least half you call it a day.

[ssid, 2016/12/14 02:59:32]

Done.

[ssid, 2016/12/14 06:18:58]

Release builds do not make the memory resident even after memset.
I have to add this line to make it resident:
for (int i = 0; i < kBufSize; i += (buf[i] == 0x42);
Removed this bit and testing the parsing code with temp file.

+    mdp.PollFastMemoryTotal(&value);
+    EXPECT_GT(value, 0u);
+  }
+#if defined(OS_LINUX) || defined(OS_ANDROID)
+  EXPECT_GT(mdp.proc_statm_file_, 0);

[Primiano Tucci (use gerrit), 2016/12/13 20:02:39]

s/GT/GE/.
In an extremely unlikely scenario, one might close all file descriptors and if
yours is the first open() will get fd 0.
will almost never happen, but for pure sake of consistency this should be >= 0

[ssid, 2016/12/14 02:59:32]

Done.

+  mdp.SetFastMemoryPollingEnabled(false);
+  EXPECT_EQ(-1, mdp.proc_statm_file_);
+#else
+  mdp.SetFastMemoryPollingEnabled(false);
+#endif
+}
+
 }  // namespace tracing