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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #include "base/metrics/field_trial.h" | 5 #include "base/metrics/field_trial.h" |
6 | 6 |
7 #include <algorithm> | 7 #include <algorithm> |
8 #include <utility> | 8 #include <utility> |
9 | 9 |
10 #include "base/base_switches.h" | 10 #include "base/base_switches.h" |
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28 const char kPersistentStringSeparator = '/'; // Currently a slash. | 28 const char kPersistentStringSeparator = '/'; // Currently a slash. |
29 | 29 |
30 // Define a marker character to be used as a prefix to a trial name on the | 30 // Define a marker character to be used as a prefix to a trial name on the |
31 // command line which forces its activation. | 31 // command line which forces its activation. |
32 const char kActivationMarker = '*'; | 32 const char kActivationMarker = '*'; |
33 | 33 |
34 // Use shared memory to communicate field trial (experiment) state. Set to false | 34 // Use shared memory to communicate field trial (experiment) state. Set to false |
35 // for now while the implementation is fleshed out (e.g. data format, single | 35 // for now while the implementation is fleshed out (e.g. data format, single |
36 // shared memory segment). See https://codereview.chromium.org/2365273004/ and | 36 // shared memory segment). See https://codereview.chromium.org/2365273004/ and |
37 // crbug.com/653874 | 37 // crbug.com/653874 |
38 #if defined(OS_WIN) | |
39 const bool kUseSharedMemoryForFieldTrials = false; | 38 const bool kUseSharedMemoryForFieldTrials = false; |
40 #endif | 39 |
40 // Constants for the field trial allocator. | |
41 const char kAllocatorName[] = "FieldTrialAllocator"; | |
42 const uint32_t kFieldTrialType = 0xABA17E13 + 1; // SHA1(FieldTrialEntry) v1 | |
43 | |
44 // We create one FieldTrialEntry struct per field trial in shared memory (via | |
45 // field_trial_allocator). It contains whether or not it's activated, and the | |
46 // offset from the start of the allocated memory to the group name. We don't | |
47 // need the offset into the trial name because that's always a fixed position | |
48 // from the start of the struct. Two strings will be appended to the end of this | |
49 // structure in allocated memory, so the result will look like this: | |
50 // --------------------------------- | |
51 // | fte | trial_name | group_name | | |
52 // --------------------------------- | |
53 struct FieldTrialEntry { | |
54 bool activated; | |
55 uint32_t group_name_offset; | |
56 | |
57 const char* GetTrialName() const { | |
58 const char* src = | |
59 reinterpret_cast<char*>(const_cast<FieldTrialEntry*>(this)); | |
60 return src + sizeof(FieldTrialEntry); | |
61 } | |
62 | |
63 const char* GetGroupName() const { | |
64 const char* src = | |
65 reinterpret_cast<char*>(const_cast<FieldTrialEntry*>(this)); | |
66 return src + this->group_name_offset; | |
67 } | |
68 }; | |
41 | 69 |
42 // Created a time value based on |year|, |month| and |day_of_month| parameters. | 70 // Created a time value based on |year|, |month| and |day_of_month| parameters. |
43 Time CreateTimeFromParams(int year, int month, int day_of_month) { | 71 Time CreateTimeFromParams(int year, int month, int day_of_month) { |
44 DCHECK_GT(year, 1970); | 72 DCHECK_GT(year, 1970); |
45 DCHECK_GT(month, 0); | 73 DCHECK_GT(month, 0); |
46 DCHECK_LT(month, 13); | 74 DCHECK_LT(month, 13); |
47 DCHECK_GT(day_of_month, 0); | 75 DCHECK_GT(day_of_month, 0); |
48 DCHECK_LT(day_of_month, 32); | 76 DCHECK_LT(day_of_month, 32); |
49 | 77 |
50 Time::Exploded exploded; | 78 Time::Exploded exploded; |
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122 entries->push_back(entry); | 150 entries->push_back(entry); |
123 } | 151 } |
124 return true; | 152 return true; |
125 } | 153 } |
126 | 154 |
127 } // namespace | 155 } // namespace |
128 | 156 |
129 // statics | 157 // statics |
130 const int FieldTrial::kNotFinalized = -1; | 158 const int FieldTrial::kNotFinalized = -1; |
131 const int FieldTrial::kDefaultGroupNumber = 0; | 159 const int FieldTrial::kDefaultGroupNumber = 0; |
160 const int kFieldTrialAllocationSize = 4 << 10; // 4 KiB = one page | |
132 bool FieldTrial::enable_benchmarking_ = false; | 161 bool FieldTrial::enable_benchmarking_ = false; |
133 | 162 |
134 int FieldTrialList::kNoExpirationYear = 0; | 163 int FieldTrialList::kNoExpirationYear = 0; |
135 | 164 |
136 //------------------------------------------------------------------------------ | 165 //------------------------------------------------------------------------------ |
137 // FieldTrial methods and members. | 166 // FieldTrial methods and members. |
138 | 167 |
139 FieldTrial::EntropyProvider::~EntropyProvider() { | 168 FieldTrial::EntropyProvider::~EntropyProvider() { |
140 } | 169 } |
141 | 170 |
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325 observer_list_(new ObserverListThreadSafe<FieldTrialList::Observer>( | 354 observer_list_(new ObserverListThreadSafe<FieldTrialList::Observer>( |
326 ObserverListBase<FieldTrialList::Observer>::NOTIFY_EXISTING_ONLY)) { | 355 ObserverListBase<FieldTrialList::Observer>::NOTIFY_EXISTING_ONLY)) { |
327 DCHECK(!global_); | 356 DCHECK(!global_); |
328 DCHECK(!used_without_global_); | 357 DCHECK(!used_without_global_); |
329 global_ = this; | 358 global_ = this; |
330 | 359 |
331 Time two_years_from_build_time = GetBuildTime() + TimeDelta::FromDays(730); | 360 Time two_years_from_build_time = GetBuildTime() + TimeDelta::FromDays(730); |
332 Time::Exploded exploded; | 361 Time::Exploded exploded; |
333 two_years_from_build_time.LocalExplode(&exploded); | 362 two_years_from_build_time.LocalExplode(&exploded); |
334 kNoExpirationYear = exploded.year; | 363 kNoExpirationYear = exploded.year; |
364 | |
365 field_trial_allocator = nullptr; | |
366 #if defined(OS_WIN) | |
367 readonly_allocator_handle = 0; | |
368 #endif | |
335 } | 369 } |
336 | 370 |
337 FieldTrialList::~FieldTrialList() { | 371 FieldTrialList::~FieldTrialList() { |
338 AutoLock auto_lock(lock_); | 372 AutoLock auto_lock(lock_); |
339 while (!registered_.empty()) { | 373 while (!registered_.empty()) { |
340 RegistrationMap::iterator it = registered_.begin(); | 374 RegistrationMap::iterator it = registered_.begin(); |
341 it->second->Release(); | 375 it->second->Release(); |
342 registered_.erase(it->first); | 376 registered_.erase(it->first); |
343 } | 377 } |
344 DCHECK_EQ(this, global_); | 378 DCHECK_EQ(this, global_); |
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579 std::string arg = cmd_line.GetSwitchValueASCII(field_trial_handle_switch); | 613 std::string arg = cmd_line.GetSwitchValueASCII(field_trial_handle_switch); |
580 size_t token = arg.find(","); | 614 size_t token = arg.find(","); |
581 int field_trial_handle = std::stoi(arg.substr(0, token)); | 615 int field_trial_handle = std::stoi(arg.substr(0, token)); |
582 int field_trial_length = std::stoi(arg.substr(token + 1, arg.length())); | 616 int field_trial_length = std::stoi(arg.substr(token + 1, arg.length())); |
583 | 617 |
584 HANDLE handle = reinterpret_cast<HANDLE>(field_trial_handle); | 618 HANDLE handle = reinterpret_cast<HANDLE>(field_trial_handle); |
585 base::SharedMemoryHandle shm_handle = | 619 base::SharedMemoryHandle shm_handle = |
586 base::SharedMemoryHandle(handle, base::GetCurrentProcId()); | 620 base::SharedMemoryHandle(handle, base::GetCurrentProcId()); |
587 | 621 |
588 // Gets deleted when it gets out of scope, but that's OK because we need it | 622 // Gets deleted when it gets out of scope, but that's OK because we need it |
589 // only for the duration of this call currently anyway. | 623 // only for the duration of this method. |
590 base::SharedMemory shared_memory(shm_handle, false); | 624 std::unique_ptr<base::SharedMemory> shm( |
591 shared_memory.Map(field_trial_length); | 625 new base::SharedMemory(shm_handle, true)); |
592 | 626 if (shm.get()->Map(field_trial_length)) |
Alexei Svitkine (slow)
2016/10/21 18:20:26
I think we should treat this failure as fatal (i.e
lawrencewu
2016/10/21 20:23:13
Done.
| |
593 char* field_trial_state = static_cast<char*>(shared_memory.memory()); | 627 FieldTrialList::CreateTrialsFromSharedMemory(std::move(shm)); |
594 bool result = FieldTrialList::CreateTrialsFromString( | |
595 std::string(field_trial_state), std::set<std::string>()); | |
596 DCHECK(result); | |
597 return; | 628 return; |
598 } | 629 } |
599 #endif | 630 #endif |
600 | 631 |
601 if (cmd_line.HasSwitch(switches::kForceFieldTrials)) { | 632 if (cmd_line.HasSwitch(switches::kForceFieldTrials)) { |
602 bool result = FieldTrialList::CreateTrialsFromString( | 633 bool result = FieldTrialList::CreateTrialsFromString( |
603 cmd_line.GetSwitchValueASCII(switches::kForceFieldTrials), | 634 cmd_line.GetSwitchValueASCII(switches::kForceFieldTrials), |
604 std::set<std::string>()); | 635 std::set<std::string>()); |
605 DCHECK(result); | 636 DCHECK(result); |
606 } | 637 } |
607 } | 638 } |
608 | 639 |
640 #if defined(OS_WIN) | |
641 // static | |
642 void FieldTrialList::AppendFieldTrialHandleIfNeeded( | |
643 base::HandlesToInheritVector* handles) { | |
644 FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded(); | |
645 | |
646 // Need to get a new, read-only handle to share to the child. | |
647 handles->push_back(global_->readonly_allocator_handle); | |
648 } | |
649 #endif | |
650 | |
651 // static | |
652 void FieldTrialList::CreateTrialsFromSharedMemory( | |
653 std::unique_ptr<base::SharedMemory> shm) { | |
654 const base::SharedPersistentMemoryAllocator shalloc(std::move(shm), 0, | |
655 kAllocatorName, true); | |
656 base::PersistentMemoryAllocator::Iterator iter(&shalloc); | |
657 | |
658 base::SharedPersistentMemoryAllocator::Reference ref; | |
659 while ((ref = iter.GetNextOfType(kFieldTrialType)) != | |
660 base::SharedPersistentMemoryAllocator::kReferenceNull) { | |
661 const FieldTrialEntry* entry = | |
662 shalloc.GetAsObject<const FieldTrialEntry>(ref, kFieldTrialType); | |
663 FieldTrial* trial = | |
664 CreateFieldTrial(entry->GetTrialName(), entry->GetGroupName()); | |
665 | |
666 if (entry->activated) { | |
667 // Call |group()| to mark the trial as "used" and notify observers, if | |
668 // any. This is useful to ensure that field trials created in child | |
669 // processes are properly reported in crash reports. | |
670 trial->group(); | |
671 } | |
672 } | |
673 } | |
674 | |
609 // static | 675 // static |
610 std::unique_ptr<base::SharedMemory> FieldTrialList::CopyFieldTrialStateToFlags( | 676 void FieldTrialList::CopyFieldTrialStateToFlags( |
611 const char* field_trial_handle_switch, | 677 const char* field_trial_handle_switch, |
612 base::CommandLine* cmd_line) { | 678 base::CommandLine* cmd_line) { |
679 #if defined(OS_WIN) | |
680 // Use shared memory to pass the state if the feature is enabled, otherwise | |
681 // fallback to passing it via the command line as a string. | |
682 if (kUseSharedMemoryForFieldTrials) { | |
683 FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded(); | |
684 // HANDLE is just typedef'd to void *. We basically cast the handle into an | |
685 // int (uintptr_t, to be exact), stringify the int, and pass it as a | |
686 // command-line flag. The child process will do the reverse conversions to | |
687 // retrieve the handle. See http://stackoverflow.com/a/153077 | |
688 auto uintptr_handle = | |
689 reinterpret_cast<uintptr_t>(global_->readonly_allocator_handle); | |
690 size_t field_trial_length = | |
691 global_->field_trial_allocator->shared_memory()->mapped_size(); | |
692 std::string field_trial_handle = std::to_string(uintptr_handle) + "," + | |
693 std::to_string(field_trial_length); | |
694 | |
695 cmd_line->AppendSwitchASCII(field_trial_handle_switch, field_trial_handle); | |
696 return; | |
697 } | |
698 #endif | |
699 | |
613 std::string field_trial_states; | 700 std::string field_trial_states; |
614 base::FieldTrialList::AllStatesToString(&field_trial_states); | 701 base::FieldTrialList::AllStatesToString(&field_trial_states); |
615 if (!field_trial_states.empty()) { | 702 if (!field_trial_states.empty()) { |
616 // Use shared memory to pass the state if the feature is enabled, otherwise | |
617 // fallback to passing it via the command line as a string. | |
618 #if defined(OS_WIN) | |
619 if (kUseSharedMemoryForFieldTrials) { | |
620 std::unique_ptr<base::SharedMemory> shm(new base::SharedMemory()); | |
621 size_t length = field_trial_states.size() + 1; | |
622 shm->CreateAndMapAnonymous(length); | |
623 memcpy(shm->memory(), field_trial_states.c_str(), length); | |
624 | |
625 // HANDLE is just typedef'd to void * | |
626 auto uintptr_handle = | |
627 reinterpret_cast<std::uintptr_t>(shm->handle().GetHandle()); | |
628 std::string field_trial_handle = | |
629 std::to_string(uintptr_handle) + "," + std::to_string(length); | |
630 | |
631 cmd_line->AppendSwitchASCII(field_trial_handle_switch, | |
632 field_trial_handle); | |
633 return shm; | |
634 } | |
635 #endif | |
636 cmd_line->AppendSwitchASCII(switches::kForceFieldTrials, | 703 cmd_line->AppendSwitchASCII(switches::kForceFieldTrials, |
637 field_trial_states); | 704 field_trial_states); |
638 } | 705 } |
639 return std::unique_ptr<base::SharedMemory>(nullptr); | |
640 } | 706 } |
641 | 707 |
642 // static | 708 // static |
643 FieldTrial* FieldTrialList::CreateFieldTrial( | 709 FieldTrial* FieldTrialList::CreateFieldTrial( |
644 const std::string& name, | 710 const std::string& name, |
645 const std::string& group_name) { | 711 const std::string& group_name) { |
646 DCHECK(global_); | 712 DCHECK(global_); |
647 DCHECK_GE(name.size(), 0u); | 713 DCHECK_GE(name.size(), 0u); |
648 DCHECK_GE(group_name.size(), 0u); | 714 DCHECK_GE(group_name.size(), 0u); |
649 if (name.empty() || group_name.empty() || !global_) | 715 if (name.empty() || group_name.empty() || !global_) |
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682 // static | 748 // static |
683 void FieldTrialList::NotifyFieldTrialGroupSelection(FieldTrial* field_trial) { | 749 void FieldTrialList::NotifyFieldTrialGroupSelection(FieldTrial* field_trial) { |
684 if (!global_) | 750 if (!global_) |
685 return; | 751 return; |
686 | 752 |
687 { | 753 { |
688 AutoLock auto_lock(global_->lock_); | 754 AutoLock auto_lock(global_->lock_); |
689 if (field_trial->group_reported_) | 755 if (field_trial->group_reported_) |
690 return; | 756 return; |
691 field_trial->group_reported_ = true; | 757 field_trial->group_reported_ = true; |
758 | |
759 if (!field_trial->enable_field_trial_) | |
760 return; | |
761 | |
762 if (kUseSharedMemoryForFieldTrials) { | |
Alexei Svitkine (slow)
2016/10/21 18:20:26
Nit: No {}'s for 1-line ifs.
lawrencewu
2016/10/21 20:23:13
Done.
| |
763 FieldTrialList::UpdateFieldTrialAllocatorWhileLocked(field_trial); | |
764 } | |
692 } | 765 } |
693 | 766 |
694 if (!field_trial->enable_field_trial_) | |
695 return; | |
696 | |
697 global_->observer_list_->Notify( | 767 global_->observer_list_->Notify( |
698 FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized, | 768 FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized, |
699 field_trial->trial_name(), field_trial->group_name_internal()); | 769 field_trial->trial_name(), field_trial->group_name_internal()); |
700 } | 770 } |
701 | 771 |
702 // static | 772 // static |
773 void FieldTrialList::InstantiateFieldTrialAllocatorIfNeeded() { | |
774 AutoLock auto_lock(global_->lock_); | |
775 // Create the allocator if not already created and add all existing trials. | |
776 if (global_->field_trial_allocator == nullptr) { | |
Alexei Svitkine (slow)
2016/10/21 18:20:26
Nit: Change this to != and an early return
lawrencewu
2016/10/21 20:23:13
Done.
| |
777 std::unique_ptr<base::SharedMemory> shm(new base::SharedMemory()); | |
778 shm->CreateAndMapAnonymous(kFieldTrialAllocationSize); | |
779 | |
780 // TODO(lawrencewu): call UpdateTrackingHistograms() when all field trials | |
781 // have been registered (perhaps in the destructor?) | |
782 global_->field_trial_allocator.reset( | |
783 new base::SharedPersistentMemoryAllocator(std::move(shm), 0, | |
784 kAllocatorName, false)); | |
785 global_->field_trial_allocator->CreateTrackingHistograms(kAllocatorName); | |
786 | |
787 // Add all existing field trials. | |
788 for (const auto& registered : global_->registered_) { | |
789 FieldTrialList::UpdateFieldTrialAllocatorWhileLocked(registered.second); | |
790 } | |
791 | |
792 #if defined(OS_WIN) | |
793 // Duplicate and set |readonly_allocator_handle| so we can pass it to be | |
794 // inherited and via the command line. | |
795 HANDLE src = | |
Alexei Svitkine (slow)
2016/10/21 18:20:26
Can you make a helper function for this in the ano
lawrencewu
2016/10/21 20:23:13
Done.
| |
796 global_->field_trial_allocator->shared_memory()->handle().GetHandle(); | |
797 ProcessHandle process = GetCurrentProcess(); | |
798 DWORD access = SECTION_MAP_READ | SECTION_QUERY; | |
799 ::DuplicateHandle(process, src, process, | |
800 &(global_->readonly_allocator_handle), access, true, 0); | |
Alexei Svitkine (slow)
2016/10/21 18:20:26
Nit: No need for ()'s
lawrencewu
2016/10/21 20:23:13
Acknowledged but don't need this anymore.
| |
801 #endif | |
802 } | |
803 } | |
804 | |
805 // static | |
806 void FieldTrialList::UpdateFieldTrialAllocatorWhileLocked( | |
807 FieldTrial* field_trial) { | |
Alexei Svitkine (slow)
2016/10/21 18:20:26
Sorry for going back and forth on this, but how ab
lawrencewu
2016/10/21 20:23:13
Done.
| |
808 // Don't do anything if the allocator hasn't been instantiated yet. | |
809 if (global_->field_trial_allocator == nullptr) | |
810 return; | |
811 | |
812 // We allocate just enough memory to fit the FTE struct, trial name, and group | |
813 // name. If there's no more memory available, quit early. | |
814 FieldTrial::State trial_state; | |
815 field_trial->GetState(&trial_state); | |
816 | |
817 std::string trial_name; | |
818 trial_state.trial_name.CopyToString(&trial_name); | |
819 size_t trial_name_size = trial_name.size() + 1; | |
820 | |
821 std::string group_name; | |
822 trial_state.group_name.CopyToString(&group_name); | |
823 size_t group_name_size = group_name.size() + 1; | |
824 | |
825 uint32_t trial_name_offset = sizeof(FieldTrialEntry); | |
826 uint32_t group_name_offset = trial_name_offset + trial_name_size; | |
827 size_t size = sizeof(FieldTrialEntry) + trial_name_size + group_name_size; | |
828 | |
829 base::SharedPersistentMemoryAllocator::Reference ref = | |
830 global_->field_trial_allocator->Allocate(size, kFieldTrialType); | |
831 if (ref == base::SharedPersistentMemoryAllocator::kReferenceNull) | |
832 return; | |
833 | |
834 FieldTrialEntry* dst = | |
835 global_->field_trial_allocator->GetAsObject<FieldTrialEntry>( | |
836 ref, kFieldTrialType); | |
837 FieldTrialEntry entry = {trial_state.activated, group_name_offset}; | |
838 *dst = entry; | |
839 memcpy(reinterpret_cast<char*>(dst) + trial_name_offset, trial_name.c_str(), | |
840 trial_name_size); | |
841 memcpy(reinterpret_cast<char*>(dst) + group_name_offset, group_name.c_str(), | |
842 group_name_size); | |
843 | |
844 global_->field_trial_allocator->MakeIterable(ref); | |
845 } | |
846 | |
847 // static | |
703 size_t FieldTrialList::GetFieldTrialCount() { | 848 size_t FieldTrialList::GetFieldTrialCount() { |
704 if (!global_) | 849 if (!global_) |
705 return 0; | 850 return 0; |
706 AutoLock auto_lock(global_->lock_); | 851 AutoLock auto_lock(global_->lock_); |
707 return global_->registered_.size(); | 852 return global_->registered_.size(); |
708 } | 853 } |
709 | 854 |
710 // static | 855 // static |
711 const FieldTrial::EntropyProvider* | 856 const FieldTrial::EntropyProvider* |
712 FieldTrialList::GetEntropyProviderForOneTimeRandomization() { | 857 FieldTrialList::GetEntropyProviderForOneTimeRandomization() { |
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732 return; | 877 return; |
733 } | 878 } |
734 AutoLock auto_lock(global_->lock_); | 879 AutoLock auto_lock(global_->lock_); |
735 CHECK(!global_->PreLockedFind(trial->trial_name())) << trial->trial_name(); | 880 CHECK(!global_->PreLockedFind(trial->trial_name())) << trial->trial_name(); |
736 trial->AddRef(); | 881 trial->AddRef(); |
737 trial->SetTrialRegistered(); | 882 trial->SetTrialRegistered(); |
738 global_->registered_[trial->trial_name()] = trial; | 883 global_->registered_[trial->trial_name()] = trial; |
739 } | 884 } |
740 | 885 |
741 } // namespace base | 886 } // namespace base |
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