[memory-infra] Implement PollFastMemoryTotal in ProcessMetricsMemoryDumpProvider.

components/tracing/common/process_metrics_memory_dump_provider_unittest.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/tracing/common/process_metrics_memory_dump_provider.h"
 
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/files/file_util.h"
 #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"
 
 namespace tracing {
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
 namespace {
 const char kTestSmaps1[] =
     "00400000-004be000 r-xp 00000000 fc:01 1234              /file/1\n"
     "Size:                760 kB\n"
@@ skipping 202 matching lines @@
   EXPECT_EQ("", regions_2[0].mapped_file);
   EXPECT_EQ(32 * 1024UL, regions_2[0].byte_stats_proportional_resident);
   EXPECT_EQ(16 * 1024UL, regions_2[0].byte_stats_shared_clean_resident);
   EXPECT_EQ(12 * 1024UL, regions_2[0].byte_stats_shared_dirty_resident);
   EXPECT_EQ(8 * 1024UL, regions_2[0].byte_stats_private_clean_resident);
   EXPECT_EQ(4 * 1024UL, regions_2[0].byte_stats_private_dirty_resident);
   EXPECT_EQ(0 * 1024UL, regions_2[0].byte_stats_swapped);
 }
 #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