1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "src/v8.h"
6 
7 #include "src/runtime-profiler.h"
8 
9 #include "src/assembler.h"
10 #include "src/base/platform/platform.h"
11 #include "src/bootstrapper.h"
12 #include "src/code-stubs.h"
13 #include "src/compilation-cache.h"
14 #include "src/execution.h"
15 #include "src/full-codegen.h"
16 #include "src/global-handles.h"
17 #include "src/heap/mark-compact.h"
18 #include "src/isolate-inl.h"
19 #include "src/scopeinfo.h"
20 
21 namespace v8 {
22 namespace internal {
23 
24 
25 // Number of times a function has to be seen on the stack before it is
26 // optimized.
27 static const int kProfilerTicksBeforeOptimization = 2;
28 // If the function optimization was disabled due to high deoptimization count,
29 // but the function is hot and has been seen on the stack this number of times,
30 // then we try to reenable optimization for this function.
31 static const int kProfilerTicksBeforeReenablingOptimization = 250;
32 // If a function does not have enough type info (according to
33 // FLAG_type_info_threshold), but has seen a huge number of ticks,
34 // optimize it as it is.
35 static const int kTicksWhenNotEnoughTypeInfo = 100;
36 // We only have one byte to store the number of ticks.
37 STATIC_ASSERT(kProfilerTicksBeforeOptimization < 256);
38 STATIC_ASSERT(kProfilerTicksBeforeReenablingOptimization < 256);
39 STATIC_ASSERT(kTicksWhenNotEnoughTypeInfo < 256);
40 
41 // Maximum size in bytes of generate code for a function to allow OSR.
42 static const int kOSRCodeSizeAllowanceBase =
43     100 * FullCodeGenerator::kCodeSizeMultiplier;
44 
45 static const int kOSRCodeSizeAllowancePerTick =
46     4 * FullCodeGenerator::kCodeSizeMultiplier;
47 
48 // Maximum size in bytes of generated code for a function to be optimized
49 // the very first time it is seen on the stack.
50 static const int kMaxSizeEarlyOpt =
51     5 * FullCodeGenerator::kCodeSizeMultiplier;
52 
53 
RuntimeProfiler(Isolate * isolate)54 RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
55     : isolate_(isolate),
56       any_ic_changed_(false) {
57 }
58 
59 
GetICCounts(Code * shared_code,int * ic_with_type_info_count,int * ic_generic_count,int * ic_total_count,int * type_info_percentage,int * generic_percentage)60 static void GetICCounts(Code* shared_code, int* ic_with_type_info_count,
61                         int* ic_generic_count, int* ic_total_count,
62                         int* type_info_percentage, int* generic_percentage) {
63   *ic_total_count = 0;
64   *ic_generic_count = 0;
65   *ic_with_type_info_count = 0;
66   Object* raw_info = shared_code->type_feedback_info();
67   if (raw_info->IsTypeFeedbackInfo()) {
68     TypeFeedbackInfo* info = TypeFeedbackInfo::cast(raw_info);
69     *ic_with_type_info_count = info->ic_with_type_info_count();
70     *ic_generic_count = info->ic_generic_count();
71     *ic_total_count = info->ic_total_count();
72   }
73   if (*ic_total_count > 0) {
74     *type_info_percentage = 100 * *ic_with_type_info_count / *ic_total_count;
75     *generic_percentage = 100 * *ic_generic_count / *ic_total_count;
76   } else {
77     *type_info_percentage = 100;  // Compared against lower bound.
78     *generic_percentage = 0;      // Compared against upper bound.
79   }
80 }
81 
82 
Optimize(JSFunction * function,const char * reason)83 void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
84   DCHECK(function->IsOptimizable());
85 
86   if (FLAG_trace_opt && function->PassesFilter(FLAG_hydrogen_filter)) {
87     PrintF("[marking ");
88     function->ShortPrint();
89     PrintF(" for recompilation, reason: %s", reason);
90     if (FLAG_type_info_threshold > 0) {
91       int typeinfo, generic, total, type_percentage, generic_percentage;
92       GetICCounts(function->shared()->code(), &typeinfo, &generic, &total,
93                   &type_percentage, &generic_percentage);
94       PrintF(", ICs with typeinfo: %d/%d (%d%%)", typeinfo, total,
95              type_percentage);
96       PrintF(", generic ICs: %d/%d (%d%%)", generic, total, generic_percentage);
97     }
98     PrintF("]\n");
99   }
100 
101 
102   if (isolate_->concurrent_recompilation_enabled() &&
103       !isolate_->bootstrapper()->IsActive()) {
104     if (isolate_->concurrent_osr_enabled() &&
105         isolate_->optimizing_compiler_thread()->IsQueuedForOSR(function)) {
106       // Do not attempt regular recompilation if we already queued this for OSR.
107       // TODO(yangguo): This is necessary so that we don't install optimized
108       // code on a function that is already optimized, since OSR and regular
109       // recompilation race.  This goes away as soon as OSR becomes one-shot.
110       return;
111     }
112     DCHECK(!function->IsInOptimizationQueue());
113     function->MarkForConcurrentOptimization();
114   } else {
115     // The next call to the function will trigger optimization.
116     function->MarkForOptimization();
117   }
118 }
119 
120 
AttemptOnStackReplacement(JSFunction * function,int loop_nesting_levels)121 void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function,
122                                                 int loop_nesting_levels) {
123   SharedFunctionInfo* shared = function->shared();
124   // See AlwaysFullCompiler (in compiler.cc) comment on why we need
125   // Debug::has_break_points().
126   if (!FLAG_use_osr ||
127       isolate_->DebuggerHasBreakPoints() ||
128       function->IsBuiltin()) {
129     return;
130   }
131 
132   // If the code is not optimizable, don't try OSR.
133   if (!shared->code()->optimizable()) return;
134 
135   // We are not prepared to do OSR for a function that already has an
136   // allocated arguments object.  The optimized code would bypass it for
137   // arguments accesses, which is unsound.  Don't try OSR.
138   if (shared->uses_arguments()) return;
139 
140   // We're using on-stack replacement: patch the unoptimized code so that
141   // any back edge in any unoptimized frame will trigger on-stack
142   // replacement for that frame.
143   if (FLAG_trace_osr) {
144     PrintF("[OSR - patching back edges in ");
145     function->PrintName();
146     PrintF("]\n");
147   }
148 
149   for (int i = 0; i < loop_nesting_levels; i++) {
150     BackEdgeTable::Patch(isolate_, shared->code());
151   }
152 }
153 
154 
OptimizeNow()155 void RuntimeProfiler::OptimizeNow() {
156   HandleScope scope(isolate_);
157 
158   if (isolate_->DebuggerHasBreakPoints()) return;
159 
160   DisallowHeapAllocation no_gc;
161 
162   // Run through the JavaScript frames and collect them. If we already
163   // have a sample of the function, we mark it for optimizations
164   // (eagerly or lazily).
165   int frame_count = 0;
166   int frame_count_limit = FLAG_frame_count;
167   for (JavaScriptFrameIterator it(isolate_);
168        frame_count++ < frame_count_limit && !it.done();
169        it.Advance()) {
170     JavaScriptFrame* frame = it.frame();
171     JSFunction* function = frame->function();
172 
173     SharedFunctionInfo* shared = function->shared();
174     Code* shared_code = shared->code();
175 
176     List<JSFunction*> functions(4);
177     frame->GetFunctions(&functions);
178     for (int i = functions.length(); --i >= 0; ) {
179       SharedFunctionInfo* shared_function_info = functions[i]->shared();
180       int ticks = shared_function_info->profiler_ticks();
181       if (ticks < Smi::kMaxValue) {
182         shared_function_info->set_profiler_ticks(ticks + 1);
183       }
184     }
185 
186     if (shared_code->kind() != Code::FUNCTION) continue;
187     if (function->IsInOptimizationQueue()) continue;
188 
189     if (FLAG_always_osr) {
190       AttemptOnStackReplacement(function, Code::kMaxLoopNestingMarker);
191       // Fall through and do a normal optimized compile as well.
192     } else if (!frame->is_optimized() &&
193         (function->IsMarkedForOptimization() ||
194          function->IsMarkedForConcurrentOptimization() ||
195          function->IsOptimized())) {
196       // Attempt OSR if we are still running unoptimized code even though the
197       // the function has long been marked or even already been optimized.
198       int ticks = shared_code->profiler_ticks();
199       int allowance = kOSRCodeSizeAllowanceBase +
200                       ticks * kOSRCodeSizeAllowancePerTick;
201       if (shared_code->CodeSize() > allowance) {
202         if (ticks < 255) shared_code->set_profiler_ticks(ticks + 1);
203       } else {
204         AttemptOnStackReplacement(function);
205       }
206       continue;
207     }
208 
209     // Only record top-level code on top of the execution stack and
210     // avoid optimizing excessively large scripts since top-level code
211     // will be executed only once.
212     const int kMaxToplevelSourceSize = 10 * 1024;
213     if (shared->is_toplevel() &&
214         (frame_count > 1 || shared->SourceSize() > kMaxToplevelSourceSize)) {
215       continue;
216     }
217 
218     // Do not record non-optimizable functions.
219     if (shared->optimization_disabled()) {
220       if (shared->deopt_count() >= FLAG_max_opt_count) {
221         // If optimization was disabled due to many deoptimizations,
222         // then check if the function is hot and try to reenable optimization.
223         int ticks = shared_code->profiler_ticks();
224         if (ticks >= kProfilerTicksBeforeReenablingOptimization) {
225           shared_code->set_profiler_ticks(0);
226           shared->TryReenableOptimization();
227         } else {
228           shared_code->set_profiler_ticks(ticks + 1);
229         }
230       }
231       continue;
232     }
233     if (!function->IsOptimizable()) continue;
234 
235     int ticks = shared_code->profiler_ticks();
236 
237     if (ticks >= kProfilerTicksBeforeOptimization) {
238       int typeinfo, generic, total, type_percentage, generic_percentage;
239       GetICCounts(shared_code, &typeinfo, &generic, &total, &type_percentage,
240                   &generic_percentage);
241       if (type_percentage >= FLAG_type_info_threshold &&
242           generic_percentage <= FLAG_generic_ic_threshold) {
243         // If this particular function hasn't had any ICs patched for enough
244         // ticks, optimize it now.
245         Optimize(function, "hot and stable");
246       } else if (ticks >= kTicksWhenNotEnoughTypeInfo) {
247         Optimize(function, "not much type info but very hot");
248       } else {
249         shared_code->set_profiler_ticks(ticks + 1);
250         if (FLAG_trace_opt_verbose) {
251           PrintF("[not yet optimizing ");
252           function->PrintName();
253           PrintF(", not enough type info: %d/%d (%d%%)]\n", typeinfo, total,
254                  type_percentage);
255         }
256       }
257     } else if (!any_ic_changed_ &&
258                shared_code->instruction_size() < kMaxSizeEarlyOpt) {
259       // If no IC was patched since the last tick and this function is very
260       // small, optimistically optimize it now.
261       int typeinfo, generic, total, type_percentage, generic_percentage;
262       GetICCounts(shared_code, &typeinfo, &generic, &total, &type_percentage,
263                   &generic_percentage);
264       if (type_percentage >= FLAG_type_info_threshold &&
265           generic_percentage <= FLAG_generic_ic_threshold) {
266         Optimize(function, "small function");
267       } else {
268         shared_code->set_profiler_ticks(ticks + 1);
269       }
270     } else {
271       shared_code->set_profiler_ticks(ticks + 1);
272     }
273   }
274   any_ic_changed_ = false;
275 }
276 
277 
278 } }  // namespace v8::internal
279