Index: base/metrics/field_trial.cc |
diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc |
index 4f3e0c76fcd58c606f3b98f90718f8dc63538d5f..dfcd18b39e049d20e3fb0fd7738027254021180c 100644 |
--- a/base/metrics/field_trial.cc |
+++ b/base/metrics/field_trial.cc |
@@ -35,9 +35,35 @@ const char kActivationMarker = '*'; |
// for now while the implementation is fleshed out (e.g. data format, single |
// shared memory segment). See https://codereview.chromium.org/2365273004/ and |
// crbug.com/653874 |
-#if defined(OS_WIN) |
const bool kUseSharedMemoryForFieldTrials = false; |
-#endif |
+ |
+// Constants for the field trial allocator. |
+const char kAllocatorName[] = "field_trial_allocator"; |
+const uint32_t kFieldTrialType = 0xABA17E13 + 1; // Version #1 of type |
bcwhite
2016/10/14 14:23:46
// SHA1(FieldTrialEntry) v1
So that others know w
lawrencewu
2016/10/19 16:21:28
Done.
|
+ |
+// We create one FieldTrialEntry struct per field trial in shared memory (via |
+// field_trial_allocator). It contains whether or not it's activated, and the |
+// offset from the start of the allocated memory to the group name. We don't |
+// need the offset into the trial name because that's always a fixed position |
+// from the start of the struct. Two strings will be appended to the end of this |
+// structure in allocated memory, so the result will look like this: |
+// --------------------------------- |
+// | fte | trial_name | group_name | |
+// --------------------------------- |
+struct FieldTrialEntry { |
+ bool activated; |
+ uint32_t group_name_offset; |
+}; |
+ |
+char* GetTrialName(FieldTrialEntry* fte) { |
Alexei Svitkine (slow)
2016/10/17 14:46:50
Make this actually a member of FieldTrialEntry - i
lawrencewu
2016/10/19 16:21:28
Done.
|
+ char* src = (char*)fte; |
Alexei Svitkine (slow)
2016/10/17 14:46:50
Per the style guide, you must use C++ style casts
lawrencewu
2016/10/19 16:21:28
Done.
|
+ return src + sizeof(FieldTrialEntry); |
+} |
+ |
+char* GetGroupName(FieldTrialEntry* fte) { |
+ char* src = (char*)fte; |
+ return src + fte->group_name_offset; |
+} |
// Created a time value based on |year|, |month| and |day_of_month| parameters. |
Time CreateTimeFromParams(int year, int month, int day_of_month) { |
@@ -132,6 +158,8 @@ const int FieldTrial::kDefaultGroupNumber = 0; |
bool FieldTrial::enable_benchmarking_ = false; |
int FieldTrialList::kNoExpirationYear = 0; |
+base::SharedPersistentMemoryAllocator* FieldTrialList::field_trial_allocator = |
+ nullptr; |
//------------------------------------------------------------------------------ |
// FieldTrial methods and members. |
@@ -577,23 +605,19 @@ void FieldTrialList::CreateTrialsFromCommandLine( |
#if defined(OS_WIN) |
if (cmd_line.HasSwitch(field_trial_handle_switch)) { |
std::string arg = cmd_line.GetSwitchValueASCII(field_trial_handle_switch); |
- size_t token = arg.find(","); |
- int field_trial_handle = std::stoi(arg.substr(0, token)); |
- int field_trial_length = std::stoi(arg.substr(token + 1, arg.length())); |
+ int field_trial_handle = std::stoi(arg); |
HANDLE handle = reinterpret_cast<HANDLE>(field_trial_handle); |
base::SharedMemoryHandle shm_handle = |
base::SharedMemoryHandle(handle, base::GetCurrentProcId()); |
// Gets deleted when it gets out of scope, but that's OK because we need it |
- // only for the duration of this call currently anyway. |
- base::SharedMemory shared_memory(shm_handle, false); |
- shared_memory.Map(field_trial_length); |
+ // only for the duration of this method. |
+ std::unique_ptr<base::SharedMemory> shm( |
+ new base::SharedMemory(shm_handle, false)); |
+ shm.get()->Map(4 << 10); // 4 KiB = one page |
- char* field_trial_state = static_cast<char*>(shared_memory.memory()); |
- bool result = FieldTrialList::CreateTrialsFromString( |
- std::string(field_trial_state), std::set<std::string>()); |
- DCHECK(result); |
+ FieldTrialList::CreateTrialsFromSharedMemory(std::move(shm)); |
return; |
} |
#endif |
@@ -606,37 +630,71 @@ void FieldTrialList::CreateTrialsFromCommandLine( |
} |
} |
+#if defined(OS_WIN) |
+// static |
+void FieldTrialList::AppendFieldTrialHandleIfNeeded( |
+ base::HandlesToInheritVector& handles) { |
+ if (field_trial_allocator) { |
+ handles.push_back( |
+ field_trial_allocator->shared_memory()->handle().GetHandle()); |
+ } |
+} |
+#endif |
+ |
+// static |
+void FieldTrialList::CreateTrialsFromSharedMemory( |
+ std::unique_ptr<base::SharedMemory> shm) { |
+ base::SharedPersistentMemoryAllocator shalloc(std::move(shm), 0, |
+ kAllocatorName, true); |
+ base::PersistentMemoryAllocator::Iterator iter(&shalloc); |
+ |
+ base::SharedPersistentMemoryAllocator::Reference ref; |
+ while ((ref = iter.GetNextOfType(kFieldTrialType)) != |
+ base::SharedPersistentMemoryAllocator::kReferenceNull) { |
+ FieldTrialEntry* fte = |
+ shalloc.GetAsObject<FieldTrialEntry>(ref, kFieldTrialType); |
+ char* trial_name = GetTrialName(fte); |
+ char* group_name = GetGroupName(fte); |
+ FieldTrial* trial = CreateFieldTrial(trial_name, group_name); |
+ |
+ if (fte->activated) { |
+ // Call |group()| to mark the trial as "used" and notify observers, if |
+ // any. This is useful to ensure that field trials created in child |
+ // processes are properly reported in crash reports. |
+ trial->group(); |
+ } |
+ } |
+} |
+ |
// static |
-std::unique_ptr<base::SharedMemory> FieldTrialList::CopyFieldTrialStateToFlags( |
+void FieldTrialList::CopyFieldTrialStateToFlags( |
const char* field_trial_handle_switch, |
base::CommandLine* cmd_line) { |
+#if defined(OS_WIN) |
+ // Use shared memory to pass the state if the feature is enabled, otherwise |
+ // fallback to passing it via the command line as a string. |
+ if (kUseSharedMemoryForFieldTrials) { |
+ base::SharedMemory* shm = field_trial_allocator->shared_memory(); |
+ |
+ // HANDLE is just typedef'd to void *. We basically cast the handle into an |
+ // int (uintptr_t, to be exact), stringify the int, and pass it as a |
+ // command-line flag. The child process will do the reverse conversions to |
+ // retrieve the handle. See http://stackoverflow.com/a/153077 |
+ auto uintptr_handle = |
+ reinterpret_cast<uintptr_t>(shm->handle().GetHandle()); |
+ std::string field_trial_handle = std::to_string(uintptr_handle); |
+ |
+ cmd_line->AppendSwitchASCII(field_trial_handle_switch, field_trial_handle); |
+ return; |
+ } |
+#endif |
+ |
std::string field_trial_states; |
base::FieldTrialList::AllStatesToString(&field_trial_states); |
if (!field_trial_states.empty()) { |
-// Use shared memory to pass the state if the feature is enabled, otherwise |
-// fallback to passing it via the command line as a string. |
-#if defined(OS_WIN) |
- if (kUseSharedMemoryForFieldTrials) { |
- std::unique_ptr<base::SharedMemory> shm(new base::SharedMemory()); |
- size_t length = field_trial_states.size() + 1; |
- shm->CreateAndMapAnonymous(length); |
- memcpy(shm->memory(), field_trial_states.c_str(), length); |
- |
- // HANDLE is just typedef'd to void * |
- auto uintptr_handle = |
- reinterpret_cast<std::uintptr_t>(shm->handle().GetHandle()); |
- std::string field_trial_handle = |
- std::to_string(uintptr_handle) + "," + std::to_string(length); |
- |
- cmd_line->AppendSwitchASCII(field_trial_handle_switch, |
- field_trial_handle); |
- return shm; |
- } |
-#endif |
cmd_line->AppendSwitchASCII(switches::kForceFieldTrials, |
field_trial_states); |
} |
- return std::unique_ptr<base::SharedMemory>(nullptr); |
} |
// static |
@@ -694,12 +752,56 @@ void FieldTrialList::NotifyFieldTrialGroupSelection(FieldTrial* field_trial) { |
if (!field_trial->enable_field_trial_) |
return; |
+ if (kUseSharedMemoryForFieldTrials) { |
+ FieldTrialList::UpdateFieldTrialAllocator(field_trial); |
Alexei Svitkine (slow)
2016/10/17 14:46:50
Please make this lazy.
That is, someone could use
lawrencewu
2016/10/19 16:21:28
Done.
|
+ } |
+ |
global_->observer_list_->Notify( |
FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized, |
field_trial->trial_name(), field_trial->group_name_internal()); |
} |
// static |
+void FieldTrialList::UpdateFieldTrialAllocator(FieldTrial* field_trial) { |
+ // Create the allocator if not already created. |
+ if (field_trial_allocator == nullptr) { |
+ std::unique_ptr<base::SharedMemory> shm(new base::SharedMemory()); |
+ shm->CreateAndMapAnonymous(4 << 10); // 4 KiB = one page |
+ |
+ field_trial_allocator = new base::SharedPersistentMemoryAllocator( |
+ std::move(shm), 0, kAllocatorName, false); |
bcwhite
2016/10/14 14:23:46
If you call
allocator->CreateTrackingHistograms(k
lawrencewu
2016/10/19 16:21:28
asvitkine and I decided to punt on this for later,
|
+ } |
+ |
+ // We allocate just enough memory to fit the FTE struct, trial name, and group |
+ // name. |
+ FieldTrial::State trial_state; |
+ field_trial->GetState(&trial_state); |
+ |
+ std::string trial_name; |
+ trial_state.trial_name.CopyToString(&trial_name); |
+ size_t trial_name_size = trial_name.size() + 1; |
+ |
+ std::string group_name; |
+ trial_state.group_name.CopyToString(&group_name); |
+ size_t group_name_size = group_name.size() + 1; |
+ |
+ uint32_t trial_name_offset = sizeof(FieldTrialEntry); |
+ uint32_t group_name_offset = trial_name_offset + trial_name_size; |
+ size_t size = sizeof(FieldTrialEntry) + trial_name_size + group_name_size; |
+ |
+ base::SharedPersistentMemoryAllocator::Reference ref = |
+ field_trial_allocator->Allocate(size, kFieldTrialType); |
bcwhite
2016/10/14 14:23:46
You need to handle the failure case here. If the
lawrencewu
2016/10/19 16:21:29
Done.
|
+ |
+ char* dst = field_trial_allocator->GetAsObject<char>(ref, kFieldTrialType); |
+ FieldTrialEntry fte = {trial_state.activated, group_name_offset}; |
+ memcpy(dst, &fte, sizeof(FieldTrialEntry)); |
+ memcpy(dst + trial_name_offset, trial_name.c_str(), trial_name_size); |
+ memcpy(dst + group_name_offset, group_name.c_str(), group_name_size); |
+ |
+ field_trial_allocator->MakeIterable(ref); |
+} |
+ |
+// static |
size_t FieldTrialList::GetFieldTrialCount() { |
if (!global_) |
return 0; |