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test-cpu-profiler.cc
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1 // Copyright 2010 the V8 project authors. All rights reserved.
2 //
3 // Tests of profiles generator and utilities.
4 
5 #include "v8.h"
6 #include "cpu-profiler-inl.h"
7 #include "cctest.h"
8 #include "../include/v8-profiler.h"
9 
10 using i::CodeEntry;
11 using i::CpuProfile;
12 using i::CpuProfiler;
13 using i::CpuProfilesCollection;
14 using i::ProfileGenerator;
15 using i::ProfileNode;
16 using i::ProfilerEventsProcessor;
17 using i::TokenEnumerator;
18 
19 
20 TEST(StartStop) {
21  CpuProfilesCollection profiles;
22  ProfileGenerator generator(&profiles);
23  ProfilerEventsProcessor processor(&generator);
24  processor.Start();
25  processor.Stop();
26  processor.Join();
27 }
28 
29 static v8::Persistent<v8::Context> env;
30 
31 static void InitializeVM() {
32  if (env.IsEmpty()) env = v8::Context::New();
33  v8::HandleScope scope;
34  env->Enter();
35 }
36 
37 static inline i::Address ToAddress(int n) {
38  return reinterpret_cast<i::Address>(n);
39 }
40 
41 static void EnqueueTickSampleEvent(ProfilerEventsProcessor* proc,
42  i::Address frame1,
43  i::Address frame2 = NULL,
44  i::Address frame3 = NULL) {
45  i::TickSample* sample = proc->TickSampleEvent();
46  sample->pc = frame1;
47  sample->tos = frame1;
48  sample->frames_count = 0;
49  if (frame2 != NULL) {
50  sample->stack[0] = frame2;
51  sample->frames_count = 1;
52  }
53  if (frame3 != NULL) {
54  sample->stack[1] = frame3;
55  sample->frames_count = 2;
56  }
57 }
58 
59 namespace {
60 
61 class TestSetup {
62  public:
63  TestSetup()
64  : old_flag_prof_browser_mode_(i::FLAG_prof_browser_mode) {
65  i::FLAG_prof_browser_mode = false;
66  }
67 
68  ~TestSetup() {
69  i::FLAG_prof_browser_mode = old_flag_prof_browser_mode_;
70  }
71 
72  private:
73  bool old_flag_prof_browser_mode_;
74 };
75 
76 } // namespace
77 
78 TEST(CodeEvents) {
79  InitializeVM();
80  TestSetup test_setup;
81  CpuProfilesCollection profiles;
82  profiles.StartProfiling("", 1);
83  ProfileGenerator generator(&profiles);
84  ProfilerEventsProcessor processor(&generator);
85  processor.Start();
86 
87  // Enqueue code creation events.
88  i::HandleScope scope;
89  const char* aaa_str = "aaa";
90  i::Handle<i::String> aaa_name = FACTORY->NewStringFromAscii(
91  i::Vector<const char>(aaa_str, i::StrLength(aaa_str)));
92  processor.CodeCreateEvent(i::Logger::FUNCTION_TAG,
93  *aaa_name,
94  HEAP->empty_string(),
95  0,
96  ToAddress(0x1000),
97  0x100,
98  ToAddress(0x10000));
99  processor.CodeCreateEvent(i::Logger::BUILTIN_TAG,
100  "bbb",
101  ToAddress(0x1200),
102  0x80);
103  processor.CodeCreateEvent(i::Logger::STUB_TAG, 5, ToAddress(0x1300), 0x10);
104  processor.CodeCreateEvent(i::Logger::BUILTIN_TAG,
105  "ddd",
106  ToAddress(0x1400),
107  0x80);
108  processor.CodeMoveEvent(ToAddress(0x1400), ToAddress(0x1500));
109  processor.CodeCreateEvent(i::Logger::STUB_TAG, 3, ToAddress(0x1600), 0x10);
110  processor.CodeCreateEvent(i::Logger::STUB_TAG, 4, ToAddress(0x1605), 0x10);
111  // Enqueue a tick event to enable code events processing.
112  EnqueueTickSampleEvent(&processor, ToAddress(0x1000));
113 
114  processor.Stop();
115  processor.Join();
116 
117  // Check the state of profile generator.
118  CodeEntry* entry1 = generator.code_map()->FindEntry(ToAddress(0x1000));
119  CHECK_NE(NULL, entry1);
120  CHECK_EQ(aaa_str, entry1->name());
121  CodeEntry* entry2 = generator.code_map()->FindEntry(ToAddress(0x1200));
122  CHECK_NE(NULL, entry2);
123  CHECK_EQ("bbb", entry2->name());
124  CodeEntry* entry3 = generator.code_map()->FindEntry(ToAddress(0x1300));
125  CHECK_NE(NULL, entry3);
126  CHECK_EQ("5", entry3->name());
127  CHECK_EQ(NULL, generator.code_map()->FindEntry(ToAddress(0x1400)));
128  CodeEntry* entry4 = generator.code_map()->FindEntry(ToAddress(0x1500));
129  CHECK_NE(NULL, entry4);
130  CHECK_EQ("ddd", entry4->name());
131  CHECK_EQ(NULL, generator.code_map()->FindEntry(ToAddress(0x1600)));
132 }
133 
134 
135 template<typename T>
136 static int CompareProfileNodes(const T* p1, const T* p2) {
137  return strcmp((*p1)->entry()->name(), (*p2)->entry()->name());
138 }
139 
140 TEST(TickEvents) {
141  TestSetup test_setup;
142  CpuProfilesCollection profiles;
143  profiles.StartProfiling("", 1);
144  ProfileGenerator generator(&profiles);
145  ProfilerEventsProcessor processor(&generator);
146  processor.Start();
147 
148  processor.CodeCreateEvent(i::Logger::BUILTIN_TAG,
149  "bbb",
150  ToAddress(0x1200),
151  0x80);
152  processor.CodeCreateEvent(i::Logger::STUB_TAG, 5, ToAddress(0x1300), 0x10);
153  processor.CodeCreateEvent(i::Logger::BUILTIN_TAG,
154  "ddd",
155  ToAddress(0x1400),
156  0x80);
157  EnqueueTickSampleEvent(&processor, ToAddress(0x1210));
158  EnqueueTickSampleEvent(&processor, ToAddress(0x1305), ToAddress(0x1220));
159  EnqueueTickSampleEvent(&processor,
160  ToAddress(0x1404),
161  ToAddress(0x1305),
162  ToAddress(0x1230));
163 
164  processor.Stop();
165  processor.Join();
166  CpuProfile* profile =
167  profiles.StopProfiling(TokenEnumerator::kNoSecurityToken, "", 1);
168  CHECK_NE(NULL, profile);
169 
170  // Check call trees.
171  const i::List<ProfileNode*>* top_down_root_children =
172  profile->top_down()->root()->children();
173  CHECK_EQ(1, top_down_root_children->length());
174  CHECK_EQ("bbb", top_down_root_children->last()->entry()->name());
175  const i::List<ProfileNode*>* top_down_bbb_children =
176  top_down_root_children->last()->children();
177  CHECK_EQ(1, top_down_bbb_children->length());
178  CHECK_EQ("5", top_down_bbb_children->last()->entry()->name());
179  const i::List<ProfileNode*>* top_down_stub_children =
180  top_down_bbb_children->last()->children();
181  CHECK_EQ(1, top_down_stub_children->length());
182  CHECK_EQ("ddd", top_down_stub_children->last()->entry()->name());
183  const i::List<ProfileNode*>* top_down_ddd_children =
184  top_down_stub_children->last()->children();
185  CHECK_EQ(0, top_down_ddd_children->length());
186 
187  const i::List<ProfileNode*>* bottom_up_root_children_unsorted =
188  profile->bottom_up()->root()->children();
189  CHECK_EQ(3, bottom_up_root_children_unsorted->length());
190  i::List<ProfileNode*> bottom_up_root_children(3);
191  bottom_up_root_children.AddAll(*bottom_up_root_children_unsorted);
192  bottom_up_root_children.Sort(&CompareProfileNodes);
193  CHECK_EQ("5", bottom_up_root_children[0]->entry()->name());
194  CHECK_EQ("bbb", bottom_up_root_children[1]->entry()->name());
195  CHECK_EQ("ddd", bottom_up_root_children[2]->entry()->name());
196  const i::List<ProfileNode*>* bottom_up_stub_children =
197  bottom_up_root_children[0]->children();
198  CHECK_EQ(1, bottom_up_stub_children->length());
199  CHECK_EQ("bbb", bottom_up_stub_children->last()->entry()->name());
200  const i::List<ProfileNode*>* bottom_up_bbb_children =
201  bottom_up_root_children[1]->children();
202  CHECK_EQ(0, bottom_up_bbb_children->length());
203  const i::List<ProfileNode*>* bottom_up_ddd_children =
204  bottom_up_root_children[2]->children();
205  CHECK_EQ(1, bottom_up_ddd_children->length());
206  CHECK_EQ("5", bottom_up_ddd_children->last()->entry()->name());
207  const i::List<ProfileNode*>* bottom_up_ddd_stub_children =
208  bottom_up_ddd_children->last()->children();
209  CHECK_EQ(1, bottom_up_ddd_stub_children->length());
210  CHECK_EQ("bbb", bottom_up_ddd_stub_children->last()->entry()->name());
211 }
212 
213 
214 // http://crbug/51594
215 // This test must not crash.
216 TEST(CrashIfStoppingLastNonExistentProfile) {
217  InitializeVM();
218  TestSetup test_setup;
219  CpuProfiler::SetUp();
220  CpuProfiler::StartProfiling("1");
221  CpuProfiler::StopProfiling("2");
222  CpuProfiler::StartProfiling("1");
223  CpuProfiler::StopProfiling("");
224  CpuProfiler::TearDown();
225 }
226 
227 
228 // http://code.google.com/p/v8/issues/detail?id=1398
229 // Long stacks (exceeding max frames limit) must not be erased.
230 TEST(Issue1398) {
231  TestSetup test_setup;
232  CpuProfilesCollection profiles;
233  profiles.StartProfiling("", 1);
234  ProfileGenerator generator(&profiles);
235  ProfilerEventsProcessor processor(&generator);
236  processor.Start();
237 
238  processor.CodeCreateEvent(i::Logger::BUILTIN_TAG,
239  "bbb",
240  ToAddress(0x1200),
241  0x80);
242 
243  i::TickSample* sample = processor.TickSampleEvent();
244  sample->pc = ToAddress(0x1200);
245  sample->tos = 0;
246  sample->frames_count = i::TickSample::kMaxFramesCount;
247  for (int i = 0; i < sample->frames_count; ++i) {
248  sample->stack[i] = ToAddress(0x1200);
249  }
250 
251  processor.Stop();
252  processor.Join();
253  CpuProfile* profile =
254  profiles.StopProfiling(TokenEnumerator::kNoSecurityToken, "", 1);
255  CHECK_NE(NULL, profile);
256 
257  int actual_depth = 0;
258  const ProfileNode* node = profile->top_down()->root();
259  while (node->children()->length() > 0) {
260  node = node->children()->last();
261  ++actual_depth;
262  }
263 
264  CHECK_EQ(1 + i::TickSample::kMaxFramesCount, actual_depth); // +1 for PC.
265 }
266 
267 
268 TEST(DeleteAllCpuProfiles) {
269  InitializeVM();
270  TestSetup test_setup;
271  CpuProfiler::SetUp();
272  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
273  CpuProfiler::DeleteAllProfiles();
274  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
275 
276  CpuProfiler::StartProfiling("1");
277  CpuProfiler::StopProfiling("1");
278  CHECK_EQ(1, CpuProfiler::GetProfilesCount());
279  CpuProfiler::DeleteAllProfiles();
280  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
281  CpuProfiler::StartProfiling("1");
282  CpuProfiler::StartProfiling("2");
283  CpuProfiler::StopProfiling("2");
284  CpuProfiler::StopProfiling("1");
285  CHECK_EQ(2, CpuProfiler::GetProfilesCount());
286  CpuProfiler::DeleteAllProfiles();
287  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
288 
289  // Test profiling cancellation by the 'delete' command.
290  CpuProfiler::StartProfiling("1");
291  CpuProfiler::StartProfiling("2");
292  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
293  CpuProfiler::DeleteAllProfiles();
294  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
295 
296  CpuProfiler::TearDown();
297 }
298 
299 
300 TEST(DeleteCpuProfile) {
301  v8::HandleScope scope;
302  LocalContext env;
303 
304  CHECK_EQ(0, v8::CpuProfiler::GetProfilesCount());
305  v8::Local<v8::String> name1 = v8::String::New("1");
306  v8::CpuProfiler::StartProfiling(name1);
307  const v8::CpuProfile* p1 = v8::CpuProfiler::StopProfiling(name1);
308  CHECK_NE(NULL, p1);
309  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
310  unsigned uid1 = p1->GetUid();
311  CHECK_EQ(p1, v8::CpuProfiler::FindProfile(uid1));
312  const_cast<v8::CpuProfile*>(p1)->Delete();
313  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
314  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid1));
315 
316  v8::Local<v8::String> name2 = v8::String::New("2");
317  v8::CpuProfiler::StartProfiling(name2);
318  const v8::CpuProfile* p2 = v8::CpuProfiler::StopProfiling(name2);
319  CHECK_NE(NULL, p2);
320  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
321  unsigned uid2 = p2->GetUid();
322  CHECK_NE(static_cast<int>(uid1), static_cast<int>(uid2));
323  CHECK_EQ(p2, v8::CpuProfiler::FindProfile(uid2));
324  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid1));
325  v8::Local<v8::String> name3 = v8::String::New("3");
326  v8::CpuProfiler::StartProfiling(name3);
327  const v8::CpuProfile* p3 = v8::CpuProfiler::StopProfiling(name3);
328  CHECK_NE(NULL, p3);
329  CHECK_EQ(2, v8::CpuProfiler::GetProfilesCount());
330  unsigned uid3 = p3->GetUid();
331  CHECK_NE(static_cast<int>(uid1), static_cast<int>(uid3));
332  CHECK_EQ(p3, v8::CpuProfiler::FindProfile(uid3));
333  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid1));
334  const_cast<v8::CpuProfile*>(p2)->Delete();
335  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
336  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid2));
337  CHECK_EQ(p3, v8::CpuProfiler::FindProfile(uid3));
338  const_cast<v8::CpuProfile*>(p3)->Delete();
339  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
340  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid3));
341  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid2));
342  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid1));
343 }
344 
345 
346 TEST(DeleteCpuProfileDifferentTokens) {
347  v8::HandleScope scope;
348  LocalContext env;
349 
350  CHECK_EQ(0, v8::CpuProfiler::GetProfilesCount());
351  v8::Local<v8::String> name1 = v8::String::New("1");
352  v8::CpuProfiler::StartProfiling(name1);
353  const v8::CpuProfile* p1 = v8::CpuProfiler::StopProfiling(name1);
354  CHECK_NE(NULL, p1);
355  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
356  unsigned uid1 = p1->GetUid();
357  CHECK_EQ(p1, v8::CpuProfiler::FindProfile(uid1));
358  v8::Local<v8::String> token1 = v8::String::New("token1");
359  const v8::CpuProfile* p1_t1 = v8::CpuProfiler::FindProfile(uid1, token1);
360  CHECK_NE(NULL, p1_t1);
361  CHECK_NE(p1, p1_t1);
362  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
363  const_cast<v8::CpuProfile*>(p1)->Delete();
364  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
365  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid1));
366  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid1, token1));
367  const_cast<v8::CpuProfile*>(p1_t1)->Delete();
368  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
369 
370  v8::Local<v8::String> name2 = v8::String::New("2");
371  v8::CpuProfiler::StartProfiling(name2);
372  v8::Local<v8::String> token2 = v8::String::New("token2");
373  const v8::CpuProfile* p2_t2 = v8::CpuProfiler::StopProfiling(name2, token2);
374  CHECK_NE(NULL, p2_t2);
375  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
376  unsigned uid2 = p2_t2->GetUid();
377  CHECK_NE(static_cast<int>(uid1), static_cast<int>(uid2));
378  const v8::CpuProfile* p2 = v8::CpuProfiler::FindProfile(uid2);
379  CHECK_NE(p2_t2, p2);
380  v8::Local<v8::String> name3 = v8::String::New("3");
381  v8::CpuProfiler::StartProfiling(name3);
382  const v8::CpuProfile* p3 = v8::CpuProfiler::StopProfiling(name3);
383  CHECK_NE(NULL, p3);
384  CHECK_EQ(2, v8::CpuProfiler::GetProfilesCount());
385  unsigned uid3 = p3->GetUid();
386  CHECK_NE(static_cast<int>(uid1), static_cast<int>(uid3));
387  CHECK_EQ(p3, v8::CpuProfiler::FindProfile(uid3));
388  const_cast<v8::CpuProfile*>(p2_t2)->Delete();
389  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
390  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid2));
391  CHECK_EQ(p3, v8::CpuProfiler::FindProfile(uid3));
392  const_cast<v8::CpuProfile*>(p2)->Delete();
393  CHECK_EQ(1, v8::CpuProfiler::GetProfilesCount());
394  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid2));
395  CHECK_EQ(p3, v8::CpuProfiler::FindProfile(uid3));
396  const_cast<v8::CpuProfile*>(p3)->Delete();
397  CHECK_EQ(0, CpuProfiler::GetProfilesCount());
398  CHECK_EQ(NULL, v8::CpuProfiler::FindProfile(uid3));
399 }
v8::internal::Address
byte * Address
Definition: globals.h:157
CHECK_EQ
#define CHECK_EQ(expected, value)
Definition: checks.h:219
TEST
TEST(StartStop)
Definition: test-cpu-profiler.cc:20
v8::String::New
static V8EXPORT Local< String > New(const char *data, int length=-1)
Definition: api.cc:4779
sample
TickSample * sample
Definition: test-log-stack-tracer.cc:62
v8::CpuProfiler::FindProfile
static const CpuProfile * FindProfile(unsigned uid, Handle< Value > security_token=Handle< Value >())
Definition: api.cc:6098
v8::internal::TickSample::stack
Address stack[kMaxFramesCount]
Definition: platform.h:728
v8::internal::List::last
T & last() const
Definition: list.h:91
v8::CpuProfiler::StartProfiling
static void StartProfiling(Handle< String > title)
Definition: api.cc:6109
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#define CHECK_NE(unexpected, value)
Definition: checks.h:223
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int StrLength(const char *string)
Definition: utils.h:234
T
#define T(name, string, precedence)
Definition: token.cc:48
v8::internal::CodeEntry
Definition: profile-generator.h:93
v8::internal::TickSample::kMaxFramesCount
static const int kMaxFramesCount
Definition: platform.h:727
HEAP
#define HEAP
Definition: isolate.h:1433
v8::CpuProfiler::GetProfilesCount
static int GetProfilesCount()
Definition: api.cc:6080
NULL
activate correct semantics for inheriting readonliness enable harmony semantics for typeof enable harmony enable harmony proxies enable all harmony harmony_scoping harmony_proxies harmony_scoping tracks arrays with only smi values automatically unbox arrays of doubles use crankshaft use hydrogen range analysis use hydrogen global value numbering use function inlining maximum number of AST nodes considered for a single inlining loop invariant code motion print statistics for hydrogen trace generated IR for specified phases trace register allocator trace range analysis trace representation types environment for every instruction put a break point before deoptimizing polymorphic inlining perform array bounds checks elimination use dead code elimination trace on stack replacement optimize closures cache optimized code for closures functions with arguments object loop weight for representation inference allow uint32 values on optimize frames if they are used only in safe operations track parallel recompilation enable all profiler experiments number of stack frames inspected by the profiler call recompile stub directly when self optimizing trigger profiler ticks based on counting instead of timing weight back edges by jump distance for interrupt triggering percentage of ICs that must have type info to allow optimization watch_ic_patching retry_self_opt interrupt_at_exit extra verbose compilation tracing generate extra emit comments in code disassembly enable use of SSE3 instructions if available enable use of CMOV instruction if available enable use of SAHF instruction if enable use of VFP3 instructions if available this implies enabling ARMv7 and VFP2 enable use of VFP2 instructions if available enable use of SDIV and UDIV instructions if enable loading bit constant by means of movw movt instruction enable unaligned accesses for enable use of MIPS FPU instructions if NULL
Definition: flag-definitions.h:300
v8::Handle::IsEmpty
bool IsEmpty() const
Definition: v8.h:209
FACTORY
#define FACTORY
Definition: isolate.h:1434
v8::CpuProfile::GetUid
unsigned GetUid() const
Definition: api.cc:6048
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static Persistent< Context > New(ExtensionConfiguration *extensions=NULL, Handle< ObjectTemplate > global_template=Handle< ObjectTemplate >(), Handle< Value > global_object=Handle< Value >())
Definition: api.cc:4411
v8::CpuProfiler::StopProfiling
static const CpuProfile * StopProfiling(Handle< String > title, Handle< Value > security_token=Handle< Value >())
Definition: api.cc:6116
v8::Local
Definition: v8.h:106
generator
activate correct semantics for inheriting readonliness enable harmony semantics for typeof enable harmony enable harmony proxies enable all harmony harmony_scoping harmony_proxies harmony_scoping tracks arrays with only smi values automatically unbox arrays of doubles use crankshaft use hydrogen range analysis use hydrogen global value numbering use function inlining maximum number of AST nodes considered for a single inlining loop invariant code motion print statistics for hydrogen trace generated IR for specified phases trace register allocator trace range analysis trace representation types environment for every instruction put a break point before deoptimizing polymorphic inlining perform array bounds checks elimination use dead code elimination trace on stack replacement optimize closures cache optimized code for closures functions with arguments object loop weight for representation inference allow uint32 values on optimize frames if they are used only in safe operations track parallel recompilation enable all profiler experiments number of stack frames inspected by the profiler call recompile stub directly when self optimizing trigger profiler ticks based on counting instead of timing weight back edges by jump distance for interrupt triggering percentage of ICs that must have type info to allow optimization watch_ic_patching retry_self_opt interrupt_at_exit extra verbose compilation tracing generate extra emit comments in code disassembly enable use of SSE3 instructions if available enable use of CMOV instruction if available enable use of SAHF instruction if enable use of VFP3 instructions if available this implies enabling ARMv7 and VFP2 enable use of VFP2 instructions if available enable use of SDIV and UDIV instructions if enable loading bit constant by means of movw movt instruction enable unaligned accesses for enable use of MIPS FPU instructions if expose natives in global object expose gc extension number of stack frames to capture disable builtin natives files print a stack trace if an assertion failure occurs use random jit cookie to mask large constants trace lazy optimization use adaptive optimizations prepare for turning on always opt minimum length for automatic enable preparsing maximum number of optimization attempts before giving up cache prototype transitions automatically set the debug break flag when debugger commands are in the queue always cause a debug break before aborting maximum length of function source code printed in a stack trace max size of the new max size of the old max size of executable always perform global GCs print one trace line following each garbage collection do not print trace line after scavenger collection print more details following each garbage collection print amount of external allocated memory after each time it is adjusted flush code that we expect not to use again before full gc do incremental marking steps track object counts and memory usage use caching Perform compaction on every full GC Never perform compaction on full GC testing only Compact code space on full incremental collections Default seed for initializing random generator(0, the default, means to use system random).") DEFINE_bool(use_verbose_printer