Pass the histogram shared memory region on child process launch.
This CL, behind a flag, updates the create/share flow for the histogram shared memory region between the browser process and its child processes. This allows the child processes to immediately allocate metrics from the shared memory region instead of waiting until the first browser/child IPC.
For the renderer, the shared memory region and allocator are created before the child is launched. This was already the case for the other child processes.
In the browser, the child process hosts expose the shared memory region to the ChildProcessLauncher/Helper so that the handle to the shared memory region passed to the child process on launch.
In the child, the metrics service initializes its histogram allocator to use the shared memory, on seeing the --histogram-shared-memory-region parameter.
See:
* go/improve-chrome-subprocess-metrics
Bug: 1028263, 1290457
Change-Id: I3dc7d59c42b6588dbf8ea31ca05254470d0a8b30
Low-Coverage-Reason: COVERAGE_UNDERREPORTED (crbug.com/1512202)
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4568968
Reviewed-by: Alexei Svitkine <[email protected]>
Reviewed-by: Camille Lamy <[email protected]>
Code-Coverage: [email protected] <[email protected]>
Reviewed-by: Robert Sesek <[email protected]>
Reviewed-by: Mark Seaborn <[email protected]>
Commit-Queue: Roger McFarlane <[email protected]>
Reviewed-by: Daniel Cheng <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1251503}
diff --git a/base/metrics/histogram_shared_memory_unittest.cc b/base/metrics/histogram_shared_memory_unittest.cc
index cfea625..5f24b1b 100644
--- a/base/metrics/histogram_shared_memory_unittest.cc
+++ b/base/metrics/histogram_shared_memory_unittest.cc
@@ -3,19 +3,184 @@
// found in the LICENSE file.
#include "base/metrics/histogram_shared_memory.h"
+
+#include "base/base_switches.h"
+#include "base/command_line.h"
+#include "base/metrics/persistent_histogram_allocator.h"
+#include "base/process/launch.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/test/multiprocess_test.h"
+#include "base/test/scoped_feature_list.h"
+#include "base/test/test_timeouts.h"
+#include "base/unguessable_token.h"
+#include "build/build_config.h"
#include "testing/gtest/include/gtest/gtest.h"
+#include "testing/multiprocess_func_list.h"
+
+#if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#include "base/files/platform_file.h"
+#include "base/posix/global_descriptors.h"
+#endif
namespace base {
+namespace {
-TEST(HistogramSharedMemory, Default) {
- HistogramSharedMemory default_constructed;
- EXPECT_FALSE(default_constructed.IsValid());
+constexpr size_t kArbitrarySize = 64 << 10;
+
+#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
+constexpr GlobalDescriptors::Key kArbitraryDescriptorKey = 42;
+#endif
+
+} // namespace
+
+TEST(HistogramSharedMemoryTest, Create) {
+ UnsafeSharedMemoryRegion region;
+
+ constexpr int kProcessId = 1234;
+ constexpr int kProcessType = 5678;
+ constexpr char kProcessName[] = "TestProcess";
+
+ auto shared_memory = HistogramSharedMemory::Create(
+ kProcessId, {kProcessType, kProcessName, kArbitrarySize});
+
+ ASSERT_TRUE(shared_memory.has_value());
+
+ ASSERT_TRUE(shared_memory->region.IsValid());
+ EXPECT_EQ(kArbitrarySize, shared_memory->region.GetSize());
+
+ ASSERT_TRUE(shared_memory->allocator);
+ EXPECT_EQ(kArbitrarySize, shared_memory->allocator->size());
}
-TEST(HistogramSharedMemory, Create) {
- auto memory = HistogramSharedMemory::Create(1234, {"Test", 1 << 20});
- ASSERT_TRUE(memory.has_value());
- EXPECT_TRUE(memory->IsValid());
+TEST(HistogramSharedMemoryTest, PassSharedMemoryRegion_Disabled) {
+ // Ensure the feature is disabled.
+ test::ScopedFeatureList feature_list;
+ feature_list.InitAndDisableFeature(kPassHistogramSharedMemoryOnLaunch);
+
+ // Create a shared memory region to pass.
+ auto memory = UnsafeSharedMemoryRegion::Create(kArbitrarySize);
+ ASSERT_TRUE(memory.IsValid());
+
+ // Initialize the command line and launch options.
+ CommandLine command_line = GetMultiProcessTestChildBaseCommandLine();
+ command_line.AppendSwitchASCII("type", "test-child");
+ LaunchOptions launch_options;
+
+#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
+ ScopedFD descriptor_to_share;
+#endif
+
+ // Update the launch parameters.
+ HistogramSharedMemory::AddToLaunchParameters(memory.Duplicate(),
+#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
+ kArbitraryDescriptorKey,
+ descriptor_to_share,
+#endif // BUILDFLAG(IS_POSIX)
+ &command_line, &launch_options);
+
+ // The metrics shared memory handle should NOT be added to the command line.
+ EXPECT_FALSE(command_line.HasSwitch(switches::kMetricsSharedMemoryHandle));
+}
+
+MULTIPROCESS_TEST_MAIN(InitFromLaunchParameters) {
+// On POSIX we generally use the descriptor map to look up inherited handles.
+// On most POSIX platforms we have to manually sure the mapping is updated,
+// for the purposes of this test.
+//
+// Note:
+// - This doesn't apply on Apple platforms (which use Rendezvous Keys)
+// - On Android the global descriptor table is managed by the launcher
+// service, so we don't have to manually update the mapping here.
+#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE) && !BUILDFLAG(IS_ANDROID)
+ GlobalDescriptors::GetInstance()->Set(
+ kArbitraryDescriptorKey,
+ kArbitraryDescriptorKey + GlobalDescriptors::kBaseDescriptor);
+#endif
+
+ EXPECT_FALSE(GlobalHistogramAllocator::Get());
+ // Simulate launching with the serialized parameters.
+
+ HistogramSharedMemory::InitFromLaunchParameters(
+ *CommandLine::ForCurrentProcess());
+ EXPECT_TRUE(GlobalHistogramAllocator::Get());
+ return 0;
+}
+
+using HistogramSharedMemoryTest = ::testing::TestWithParam<bool>;
+
+INSTANTIATE_TEST_SUITE_P(All,
+ HistogramSharedMemoryTest,
+ ::testing::Values(/*launch_options.elevated=*/false
+#if BUILDFLAG(IS_WIN)
+ ,
+ /*launch_options.elevated=*/true
+#endif
+ ));
+
+TEST_P(HistogramSharedMemoryTest, PassSharedMemoryRegion_Enabled) {
+ // Ensure the feature is enabled.
+ test::ScopedFeatureList feature_list;
+ feature_list.InitAndEnableFeature(kPassHistogramSharedMemoryOnLaunch);
+
+ // Create a shared memory region to pass.
+ auto memory = UnsafeSharedMemoryRegion::Create(kArbitrarySize);
+ ASSERT_TRUE(memory.IsValid());
+
+ // Initialize the command line and launch options.
+ CommandLine command_line = GetMultiProcessTestChildBaseCommandLine();
+ command_line.AppendSwitchASCII("type", "test-child");
+ LaunchOptions launch_options;
+
+ // On windows, check both the elevated and non-elevated launches.
+#if BUILDFLAG(IS_WIN)
+ launch_options.start_hidden = true;
+ launch_options.elevated = GetParam();
+#elif BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
+ ScopedFD descriptor_to_share;
+#endif
+
+ // Update the launch parameters.
+ HistogramSharedMemory::AddToLaunchParameters(memory.Duplicate(),
+#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
+ kArbitraryDescriptorKey,
+ descriptor_to_share,
+#endif
+ &command_line, &launch_options);
+
+ // The metrics shared memory handle should be added to the command line.
+ ASSERT_TRUE(command_line.HasSwitch(switches::kMetricsSharedMemoryHandle));
+ SCOPED_TRACE(
+ command_line.GetSwitchValueASCII(switches::kMetricsSharedMemoryHandle));
+
+#if BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
+ // On posix, AddToLaunchParameters() ignores the launch options and instead
+ // returns the descriptor to be shared. This is because the browser child
+ // launcher helper manages a separate list of files to share via the zygote,
+ // if available. If, like in this test scenario, there's ultimately no zygote
+ // to use, launch helper updates the launch options to share the descriptor
+ // mapping relative to a base descriptor.
+ launch_options.fds_to_remap.emplace_back(descriptor_to_share.get(),
+ kArbitraryDescriptorKey);
+ // GlobalDescriptors::GetInstance()->Set(kArbitraryDescriptorKey,
+ // descriptor_to_share);
+#if !BUILDFLAG(IS_ANDROID)
+ for (auto& pair : launch_options.fds_to_remap) {
+ pair.second += base::GlobalDescriptors::kBaseDescriptor;
+ }
+#endif // !BUILDFLAG(IS_ANDROID)
+#endif // BUILDFLAG(IS_POSIX) && !BUILDFLAG(IS_APPLE)
+
+ // Launch the child process.
+ Process process = SpawnMultiProcessTestChild("InitFromLaunchParameters",
+ command_line, launch_options);
+
+ // The child process returns non-zero if it could not open the shared memory
+ // region based on the launch parameters.
+ int exit_code;
+ EXPECT_TRUE(WaitForMultiprocessTestChildExit(
+ process, TestTimeouts::action_timeout(), &exit_code));
+ EXPECT_EQ(0, exit_code);
}
} // namespace base
