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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 // FieldTrial is a class for handling details of statistical experiments | 5 // FieldTrial is a class for handling details of statistical experiments |
6 // performed by actual users in the field (i.e., in a shipped or beta product). | 6 // performed by actual users in the field (i.e., in a shipped or beta product). |
7 // All code is called exclusively on the UI thread currently. | 7 // All code is called exclusively on the UI thread currently. |
8 // | 8 // |
9 // The simplest example is an experiment to see whether one of two options | 9 // The simplest example is an experiment to see whether one of two options |
10 // produces "better" results across our user population. In that scenario, UMA | 10 // produces "better" results across our user population. In that scenario, UMA |
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58 #include <stdint.h> | 58 #include <stdint.h> |
59 | 59 |
60 #include <map> | 60 #include <map> |
61 #include <memory> | 61 #include <memory> |
62 #include <set> | 62 #include <set> |
63 #include <string> | 63 #include <string> |
64 #include <vector> | 64 #include <vector> |
65 | 65 |
66 #include "base/base_export.h" | 66 #include "base/base_export.h" |
67 #include "base/command_line.h" | 67 #include "base/command_line.h" |
68 #include "base/files/file.h" | |
68 #include "base/gtest_prod_util.h" | 69 #include "base/gtest_prod_util.h" |
69 #include "base/macros.h" | 70 #include "base/macros.h" |
70 #include "base/memory/ref_counted.h" | 71 #include "base/memory/ref_counted.h" |
71 #include "base/memory/shared_memory.h" | 72 #include "base/memory/shared_memory.h" |
72 #include "base/metrics/persistent_memory_allocator.h" | 73 #include "base/metrics/persistent_memory_allocator.h" |
73 #include "base/observer_list_threadsafe.h" | 74 #include "base/observer_list_threadsafe.h" |
74 #include "base/process/launch.h" | 75 #include "base/process/launch.h" |
75 #include "base/strings/string_piece.h" | 76 #include "base/strings/string_piece.h" |
76 #include "base/synchronization/lock.h" | 77 #include "base/synchronization/lock.h" |
77 #include "base/time/time.h" | 78 #include "base/time/time.h" |
78 | 79 |
80 // On systems that use the zygote process to spawn child processes, we must | |
81 // retrieve the correct fd using the mapping in GlobalDescriptors. | |
82 #if defined(OS_POSIX) && !defined(OS_NACL) && !defined(OS_MACOSX) && \ | |
83 !defined(OS_ANDROID) | |
84 #define POSIX_WITH_ZYGOTE 1 | |
Alexei Svitkine (slow)
2016/11/28 16:56:13
I don't think we should define this in the header
lawrencewu
2016/11/29 14:38:07
Done.
| |
85 #endif | |
86 | |
79 namespace base { | 87 namespace base { |
80 | 88 |
81 class FieldTrialList; | 89 class FieldTrialList; |
82 | 90 |
83 class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> { | 91 class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> { |
84 public: | 92 public: |
85 typedef int Probability; // Probability type for being selected in a trial. | 93 typedef int Probability; // Probability type for being selected in a trial. |
86 | 94 |
87 // TODO(665129): Make private again after crash has been resolved. | 95 // TODO(665129): Make private again after crash has been resolved. |
88 typedef SharedPersistentMemoryAllocator::Reference FieldTrialRef; | 96 typedef SharedPersistentMemoryAllocator::Reference FieldTrialRef; |
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496 | 504 |
497 // Achieves the same thing as CreateTrialsFromString, except wraps the logic | 505 // Achieves the same thing as CreateTrialsFromString, except wraps the logic |
498 // by taking in the trials from the command line, either via shared memory | 506 // by taking in the trials from the command line, either via shared memory |
499 // handle or command line argument. | 507 // handle or command line argument. |
500 // If using shared memory to pass around the list of field trials, then | 508 // If using shared memory to pass around the list of field trials, then |
501 // expects |field_trial_handle_switch| command line argument to | 509 // expects |field_trial_handle_switch| command line argument to |
502 // contain the shared memory handle. | 510 // contain the shared memory handle. |
503 // If not, then create the trials as before (using the kForceFieldTrials | 511 // If not, then create the trials as before (using the kForceFieldTrials |
504 // switch). Needs the |field_trial_handle_switch| argument to be passed in | 512 // switch). Needs the |field_trial_handle_switch| argument to be passed in |
505 // since base/ can't depend on content/. | 513 // since base/ can't depend on content/. |
506 static void CreateTrialsFromCommandLine( | 514 static void CreateTrialsFromCommandLine(const base::CommandLine& cmd_line, |
507 const base::CommandLine& cmd_line, | 515 const char* field_trial_handle_switch, |
508 const char* field_trial_handle_switch); | 516 const int field_trial_handle); |
Alexei Svitkine (slow)
2016/11/28 16:56:13
Nit: No reason to mark primitive params (int) as c
lawrencewu
2016/11/29 14:38:07
Done.
| |
509 | 517 |
510 #if defined(OS_WIN) | 518 #if defined(OS_WIN) |
511 // On Windows, we need to explicitly pass down any handles to be inherited. | 519 // On Windows, we need to explicitly pass down any handles to be inherited. |
512 // This function adds the shared memory handle to field trial state to the | 520 // This function adds the shared memory handle to field trial state to the |
513 // list of handles to be inherited. | 521 // list of handles to be inherited. |
514 static void AppendFieldTrialHandleIfNeeded( | 522 static void AppendFieldTrialHandleIfNeeded( |
515 base::HandlesToInheritVector* handles); | 523 base::HandlesToInheritVector* handles); |
524 #elif defined(OS_POSIX) | |
525 // On POSIX, we also need to explicitly pass down this file descriptor that | |
526 // should be shared with the child process. Returns kInvalidPlatformFile if no | |
527 // handle exists or was not initialized properly. | |
528 static PlatformFile GetFieldTrialHandle(); | |
516 #endif | 529 #endif |
517 | 530 |
518 // Adds a switch to the command line containing the field trial state as a | 531 // Adds a switch to the command line containing the field trial state as a |
519 // string (if not using shared memory to share field trial state), or the | 532 // string (if not using shared memory to share field trial state), or the |
520 // shared memory handle + length. | 533 // shared memory handle + length. |
521 // Needs the |field_trial_handle_switch| argument to be passed in since base/ | 534 // Needs the |field_trial_handle_switch| argument to be passed in since base/ |
522 // can't depend on content/. | 535 // can't depend on content/. |
523 static void CopyFieldTrialStateToFlags(const char* field_trial_handle_switch, | 536 static void CopyFieldTrialStateToFlags(const char* field_trial_handle_switch, |
524 base::CommandLine* cmd_line); | 537 base::CommandLine* cmd_line); |
525 | 538 |
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551 static size_t GetFieldTrialCount(); | 564 static size_t GetFieldTrialCount(); |
552 | 565 |
553 private: | 566 private: |
554 // Allow tests to access our innards for testing purposes. | 567 // Allow tests to access our innards for testing purposes. |
555 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); | 568 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, InstantiateAllocator); |
556 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); | 569 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, AddTrialsToAllocator); |
557 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, | 570 FRIEND_TEST_ALL_PREFIXES(FieldTrialListTest, |
558 DoNotAddSimulatedFieldTrialsToAllocator); | 571 DoNotAddSimulatedFieldTrialsToAllocator); |
559 | 572 |
560 #if defined(OS_WIN) | 573 #if defined(OS_WIN) |
561 // Takes in |handle| that should have been retrieved from the command line and | 574 // Takes in |handle_switch| from the command line which represents the shared |
562 // creates a SharedMemoryHandle from it, and then calls | 575 // memory handle for field trials, parses it, and creates the field trials. |
563 // CreateTrialsFromSharedMemory(). Returns true on success, false on failure. | 576 // Returns true on success, false on failure. |
564 static bool CreateTrialsFromWindowsHandle(HANDLE handle); | 577 static bool CreateTrialsFromHandleSwitch(const std::string& handle_switch); |
565 #endif | 578 #endif |
566 | 579 |
580 #if defined(POSIX_WITH_ZYGOTE) | |
581 // On POSIX systems that use the zygote, we look up the correct fd that backs | |
582 // the shared memory segment containing the field trials by looking it up via | |
583 // an fd key in GlobalDescriptors. Returns true on success, false on failure. | |
584 static bool CreateTrialsFromFdKey(const int fd_key); | |
Alexei Svitkine (slow)
2016/11/28 16:56:13
Nit: No const
lawrencewu
2016/11/29 14:38:07
Done.
| |
585 #endif | |
586 | |
587 // Takes an unmapped SharedMemoryHandle, creates a SharedMemory object from it | |
588 // and maps it with the correct size. | |
589 static bool CreateTrialsFromSharedMemoryHandle(SharedMemoryHandle shm_handle); | |
590 | |
567 // Expects a mapped piece of shared memory |shm| that was created from the | 591 // Expects a mapped piece of shared memory |shm| that was created from the |
568 // browser process's field_trial_allocator and shared via the command line. | 592 // browser process's field_trial_allocator and shared via the command line. |
569 // This function recreates the allocator, iterates through all the field | 593 // This function recreates the allocator, iterates through all the field |
570 // trials in it, and creates them via CreateFieldTrial(). Returns true if | 594 // trials in it, and creates them via CreateFieldTrial(). Returns true if |
571 // successful and false otherwise. | 595 // successful and false otherwise. |
572 static bool CreateTrialsFromSharedMemory( | 596 static bool CreateTrialsFromSharedMemory( |
573 std::unique_ptr<base::SharedMemory> shm); | 597 std::unique_ptr<base::SharedMemory> shm); |
574 | 598 |
575 // Instantiate the field trial allocator, add all existing field trials to it, | 599 // Instantiate the field trial allocator, add all existing field trials to it, |
576 // and duplicates its handle to a read-only handle, which gets stored in | 600 // and duplicates its handle to a read-only handle, which gets stored in |
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620 | 644 |
621 // List of observers to be notified when a group is selected for a FieldTrial. | 645 // List of observers to be notified when a group is selected for a FieldTrial. |
622 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; | 646 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; |
623 | 647 |
624 // Allocator in shared memory containing field trial data. Used in both | 648 // Allocator in shared memory containing field trial data. Used in both |
625 // browser and child processes, but readonly in the child. | 649 // browser and child processes, but readonly in the child. |
626 // In the future, we may want to move this to a more generic place if we want | 650 // In the future, we may want to move this to a more generic place if we want |
627 // to start passing more data other than field trials. | 651 // to start passing more data other than field trials. |
628 std::unique_ptr<FieldTrialAllocator> field_trial_allocator_ = nullptr; | 652 std::unique_ptr<FieldTrialAllocator> field_trial_allocator_ = nullptr; |
629 | 653 |
630 #if defined(OS_WIN) | |
631 // Readonly copy of the handle to the allocator. Needs to be a member variable | 654 // Readonly copy of the handle to the allocator. Needs to be a member variable |
632 // because it's needed from both CopyFieldTrialStateToFlags() and | 655 // because it's needed from both CopyFieldTrialStateToFlags() and |
633 // AppendFieldTrialHandleIfNeeded(). | 656 // AppendFieldTrialHandleIfNeeded(). |
634 HANDLE readonly_allocator_handle_ = nullptr; | 657 PlatformFile readonly_allocator_handle_ = kInvalidPlatformFile; |
635 #endif | |
636 | 658 |
637 // Tracks whether CreateTrialsFromCommandLine() has been called. | 659 // Tracks whether CreateTrialsFromCommandLine() has been called. |
638 bool create_trials_from_command_line_called_ = false; | 660 bool create_trials_from_command_line_called_ = false; |
639 | 661 |
640 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); | 662 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); |
641 }; | 663 }; |
642 | 664 |
643 } // namespace base | 665 } // namespace base |
644 | 666 |
645 #endif // BASE_METRICS_FIELD_TRIAL_H_ | 667 #endif // BASE_METRICS_FIELD_TRIAL_H_ |
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