Index: base/metrics/field_trial.cc |
diff --git a/base/metrics/field_trial.cc b/base/metrics/field_trial.cc |
index 4f3e0c76fcd58c606f3b98f90718f8dc63538d5f..911c8e5ee9842759c3c820929e268098e6a6dbd6 100644 |
--- a/base/metrics/field_trial.cc |
+++ b/base/metrics/field_trial.cc |
@@ -12,6 +12,7 @@ |
#include "base/command_line.h" |
#include "base/feature_list.h" |
#include "base/logging.h" |
+#include "base/process/memory.h" |
#include "base/rand_util.h" |
#include "base/strings/string_number_conversions.h" |
#include "base/strings/string_util.h" |
@@ -35,10 +36,42 @@ 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; |
+ |
+// Constants for the field trial allocator. |
+const char kAllocatorName[] = "FieldTrialAllocator"; |
+const uint32_t kFieldTrialType = 0xABA17E13 + 1; // SHA1(FieldTrialEntry) v1 |
+#if !defined(OS_NACL) |
+const size_t kFieldTrialAllocationSize = 4 << 10; // 4 KiB = one page |
#endif |
+// 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 | |
+// --------------------------------- |
+// TODO(lawrencewu): Actually update the activated flag. |
+struct FieldTrialEntry { |
+ bool activated; |
+ uint32_t group_name_offset; |
+ |
+ const char* GetTrialName() const { |
+ const char* src = |
+ reinterpret_cast<char*>(const_cast<FieldTrialEntry*>(this)); |
+ return src + sizeof(FieldTrialEntry); |
+ } |
+ |
+ const char* GetGroupName() const { |
+ const char* src = |
+ reinterpret_cast<char*>(const_cast<FieldTrialEntry*>(this)); |
+ return src + this->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) { |
DCHECK_GT(year, 1970); |
@@ -124,6 +157,27 @@ bool ParseFieldTrialsString(const std::string& trials_string, |
return true; |
} |
+void AddForceFieldTrialsFlag(CommandLine* cmd_line) { |
+ std::string field_trial_states; |
+ FieldTrialList::AllStatesToString(&field_trial_states); |
+ if (!field_trial_states.empty()) { |
+ cmd_line->AppendSwitchASCII(switches::kForceFieldTrials, |
+ field_trial_states); |
+ } |
+} |
+ |
+#if defined(OS_WIN) |
+HANDLE CreateReadOnlyHandle(SharedPersistentMemoryAllocator* allocator) { |
+ HANDLE src = allocator->shared_memory()->handle().GetHandle(); |
+ ProcessHandle process = GetCurrentProcess(); |
+ DWORD access = SECTION_MAP_READ | SECTION_QUERY; |
+ HANDLE dst; |
+ if (!::DuplicateHandle(process, src, process, &dst, access, true, 0)) |
+ return nullptr; |
+ return dst; |
+} |
+#endif |
+ |
} // namespace |
// statics |
@@ -570,30 +624,28 @@ bool FieldTrialList::CreateTrialsFromString( |
// static |
void FieldTrialList::CreateTrialsFromCommandLine( |
- const base::CommandLine& cmd_line, |
+ const CommandLine& cmd_line, |
const char* field_trial_handle_switch) { |
DCHECK(global_); |
-#if defined(OS_WIN) |
+#if defined(OS_WIN) && !defined(OS_NACL) |
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())); |
+ size_t field_trial_length = std::stoi(arg.substr(token + 1, arg.length())); |
HANDLE handle = reinterpret_cast<HANDLE>(field_trial_handle); |
- base::SharedMemoryHandle shm_handle = |
- base::SharedMemoryHandle(handle, base::GetCurrentProcId()); |
+ SharedMemoryHandle shm_handle = |
+ SharedMemoryHandle(handle, 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<SharedMemory> shm(new SharedMemory(shm_handle, true)); |
+ if (!shm.get()->Map(field_trial_length)) |
+ TerminateBecauseOutOfMemory(field_trial_length); |
- 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 +658,77 @@ void FieldTrialList::CreateTrialsFromCommandLine( |
} |
} |
+#if defined(OS_WIN) |
+// static |
+void FieldTrialList::AppendFieldTrialHandleIfNeeded( |
+ HandlesToInheritVector* handles) { |
+ if (!global_) |
+ return; |
+ if (kUseSharedMemoryForFieldTrials) { |
+ InstantiateFieldTrialAllocatorIfNeeded(); |
+ if (global_->readonly_allocator_handle_) |
+ handles->push_back(global_->readonly_allocator_handle_); |
+ } |
+} |
+#endif |
+ |
// static |
-std::unique_ptr<base::SharedMemory> FieldTrialList::CopyFieldTrialStateToFlags( |
+void FieldTrialList::CreateTrialsFromSharedMemory( |
+ std::unique_ptr<SharedMemory> shm) { |
+ const SharedPersistentMemoryAllocator shalloc(std::move(shm), 0, |
+ kAllocatorName, true); |
+ PersistentMemoryAllocator::Iterator iter(&shalloc); |
+ |
+ SharedPersistentMemoryAllocator::Reference ref; |
+ while ((ref = iter.GetNextOfType(kFieldTrialType)) != |
+ SharedPersistentMemoryAllocator::kReferenceNull) { |
+ const FieldTrialEntry* entry = |
+ shalloc.GetAsObject<const FieldTrialEntry>(ref, kFieldTrialType); |
+ FieldTrial* trial = |
+ CreateFieldTrial(entry->GetTrialName(), entry->GetGroupName()); |
+ |
+ if (entry->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 |
+void FieldTrialList::CopyFieldTrialStateToFlags( |
const char* field_trial_handle_switch, |
- base::CommandLine* cmd_line) { |
- 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. |
+ CommandLine* cmd_line) { |
#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; |
+ // 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) { |
+ InstantiateFieldTrialAllocatorIfNeeded(); |
+ // If the readonly handle didn't get duplicated properly, then fallback to |
+ // original behavior. |
+ if (!global_->readonly_allocator_handle_) { |
+ AddForceFieldTrialsFlag(cmd_line); |
+ return; |
} |
-#endif |
- cmd_line->AppendSwitchASCII(switches::kForceFieldTrials, |
- field_trial_states); |
+ |
+ // 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>(global_->readonly_allocator_handle_); |
+ size_t field_trial_length = |
+ global_->field_trial_allocator_->shared_memory()->mapped_size(); |
+ std::string field_trial_handle = std::to_string(uintptr_handle) + "," + |
+ std::to_string(field_trial_length); |
+ |
+ cmd_line->AppendSwitchASCII(field_trial_handle_switch, field_trial_handle); |
+ return; |
} |
- return std::unique_ptr<base::SharedMemory>(nullptr); |
+#endif |
+ |
+ AddForceFieldTrialsFlag(cmd_line); |
} |
// static |
@@ -689,16 +781,96 @@ void FieldTrialList::NotifyFieldTrialGroupSelection(FieldTrial* field_trial) { |
if (field_trial->group_reported_) |
return; |
field_trial->group_reported_ = true; |
- } |
- if (!field_trial->enable_field_trial_) |
- return; |
+ if (!field_trial->enable_field_trial_) |
+ return; |
+ |
+ if (kUseSharedMemoryForFieldTrials) { |
+ field_trial->AddToAllocatorWhileLocked( |
+ global_->field_trial_allocator_.get()); |
+ } |
+ } |
global_->observer_list_->Notify( |
FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized, |
field_trial->trial_name(), field_trial->group_name_internal()); |
} |
+#if !defined(OS_NACL) |
+// static |
+void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() { |
+ AutoLock auto_lock(global_->lock_); |
+ // Create the allocator if not already created and add all existing trials. |
+ if (global_->field_trial_allocator_ != nullptr) |
+ return; |
+ |
+ std::unique_ptr<SharedMemory> shm(new SharedMemory()); |
+ if (!shm->CreateAndMapAnonymous(kFieldTrialAllocationSize)) |
+ TerminateBecauseOutOfMemory(kFieldTrialAllocationSize); |
+ |
+ // TODO(lawrencewu): call UpdateTrackingHistograms() when all field trials |
+ // have been registered (perhaps in the destructor?) |
+ global_->field_trial_allocator_.reset(new SharedPersistentMemoryAllocator( |
+ std::move(shm), 0, kAllocatorName, false)); |
+ global_->field_trial_allocator_->CreateTrackingHistograms(kAllocatorName); |
+ |
+ // Add all existing field trials. |
+ for (const auto& registered : global_->registered_) { |
+ registered.second->AddToAllocatorWhileLocked( |
+ global_->field_trial_allocator_.get()); |
+ } |
+ |
+#if defined(OS_WIN) |
+ // Set |readonly_allocator_handle_| so we can pass it to be inherited and via |
+ // the command line. |
+ global_->readonly_allocator_handle_ = |
+ CreateReadOnlyHandle(global_->field_trial_allocator_.get()); |
+#endif |
+} |
+#endif |
+ |
+void FieldTrial::AddToAllocatorWhileLocked( |
+ SharedPersistentMemoryAllocator* allocator) { |
+ // Don't do anything if the allocator hasn't been instantiated yet. |
+ if (allocator == nullptr) |
+ return; |
+ |
+ State trial_state; |
+ if (!GetState(&trial_state)) |
+ return; |
+ |
+ size_t trial_name_size = trial_state.trial_name.size() + 1; |
+ size_t group_name_size = trial_state.group_name.size() + 1; |
+ size_t size = sizeof(FieldTrialEntry) + trial_name_size + group_name_size; |
+ |
+ // Allocate just enough memory to fit the FieldTrialEntry struct, trial name, |
+ // and group name. |
+ SharedPersistentMemoryAllocator::Reference ref = |
+ allocator->Allocate(size, kFieldTrialType); |
+ if (ref == SharedPersistentMemoryAllocator::kReferenceNull) |
+ return; |
+ |
+ // Calculate offsets into the shared memory segment. |
+ FieldTrialEntry* entry = |
+ allocator->GetAsObject<FieldTrialEntry>(ref, kFieldTrialType); |
+ uint32_t trial_name_offset = sizeof(FieldTrialEntry); |
+ uint32_t group_name_offset = trial_name_offset + trial_name_size; |
+ |
+ // Copy over the data. |
+ entry->activated = trial_state.activated; |
+ entry->group_name_offset = group_name_offset; |
+ char* trial_name = reinterpret_cast<char*>(entry) + trial_name_offset; |
+ char* group_name = reinterpret_cast<char*>(entry) + group_name_offset; |
+ memcpy(trial_name, trial_state.trial_name.data(), trial_name_size); |
+ memcpy(group_name, trial_state.group_name.data(), group_name_size); |
+ |
+ // Null terminate the strings. |
+ trial_name[trial_state.trial_name.size()] = '\0'; |
+ group_name[trial_state.group_name.size()] = '\0'; |
+ |
+ allocator->MakeIterable(ref); |
+} |
+ |
// static |
size_t FieldTrialList::GetFieldTrialCount() { |
if (!global_) |