1 /*
   2  * Copyright (c) 2017, 2019, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #include "precompiled.hpp"
  25 #include "code/codeCache.hpp"
  26 #include "code/nmethod.hpp"
  27 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
  28 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
  29 #include "gc/shenandoah/shenandoahUtils.hpp"
  30 #include "memory/resourceArea.hpp"
  31 #include "memory/universe.hpp"
  32 
  33 ShenandoahParallelCodeCacheIterator::ShenandoahParallelCodeCacheIterator(const GrowableArray<CodeHeap*>* heaps) {
  34   _length = heaps->length();
  35   _iters = NEW_C_HEAP_ARRAY(ShenandoahParallelCodeHeapIterator, _length, mtGC);
  36   for (int h = 0; h < _length; h++) {
  37     _iters[h] = ShenandoahParallelCodeHeapIterator(heaps->at(h));
  38   }
  39 }
  40 
  41 ShenandoahParallelCodeCacheIterator::~ShenandoahParallelCodeCacheIterator() {
  42   FREE_C_HEAP_ARRAY(ParallelCodeHeapIterator, _iters);
  43 }
  44 
  45 void ShenandoahParallelCodeCacheIterator::parallel_blobs_do(CodeBlobClosure* f) {
  46   for (int c = 0; c < _length; c++) {
  47     _iters[c].parallel_blobs_do(f);
  48   }
  49 }
  50 
  51 ShenandoahParallelCodeHeapIterator::ShenandoahParallelCodeHeapIterator(CodeHeap* heap) :
  52         _heap(heap), _claimed_idx(0), _finished(false) {
  53 }
  54 
  55 void ShenandoahParallelCodeHeapIterator::parallel_blobs_do(CodeBlobClosure* f) {
  56   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
  57 
  58   /*
  59    * Parallel code heap walk.
  60    *
  61    * This code makes all threads scan all code heaps, but only one thread would execute the
  62    * closure on given blob. This is achieved by recording the "claimed" blocks: if a thread
  63    * had claimed the block, it can process all blobs in it. Others have to fast-forward to
  64    * next attempt without processing.
  65    *
  66    * Late threads would return immediately if iterator is finished.
  67    */
  68 
  69   if (_finished) {
  70     return;
  71   }
  72 
  73   int stride = 256; // educated guess
  74   int stride_mask = stride - 1;
  75   assert (is_power_of_2(stride), "sanity");
  76 
  77   int count = 0;
  78   bool process_block = true;
  79 
  80   for (CodeBlob *cb = CodeCache::first_blob(_heap); cb != NULL; cb = CodeCache::next_blob(_heap, cb)) {
  81     int current = count++;
  82     if ((current & stride_mask) == 0) {
  83       process_block = (current >= _claimed_idx) &&
  84                       (Atomic::cmpxchg(current + stride, &_claimed_idx, current) == current);
  85     }
  86     if (process_block) {
  87       if (cb->is_alive()) {
  88         f->do_code_blob(cb);
  89 #ifdef ASSERT
  90         if (cb->is_nmethod())
  91           Universe::heap()->verify_nmethod((nmethod*)cb);
  92 #endif
  93       }
  94     }
  95   }
  96 
  97   _finished = true;
  98 }
  99 
 100 class ShenandoahNMethodOopDetector : public OopClosure {
 101 private:
 102   ResourceMark rm; // For growable array allocation below.
 103   GrowableArray<oop*> _oops;
 104 
 105 public:
 106   ShenandoahNMethodOopDetector() : _oops(10) {};
 107 
 108   void do_oop(oop* o) {
 109     _oops.append(o);
 110   }
 111   void do_oop(narrowOop* o) {
 112     fatal("NMethods should not have compressed oops embedded.");
 113   }
 114 
 115   GrowableArray<oop*>* oops() {
 116     return &_oops;
 117   }
 118 
 119   bool has_oops() {
 120     return !_oops.is_empty();
 121   }
 122 };
 123 
 124 GrowableArray<ShenandoahNMethod*>* ShenandoahCodeRoots::_recorded_nms;
 125 ShenandoahLock                     ShenandoahCodeRoots::_recorded_nms_lock;
 126 
 127 void ShenandoahCodeRoots::initialize() {
 128   _recorded_nms = new (ResourceObj::C_HEAP, mtGC) GrowableArray<ShenandoahNMethod*>(100, true, mtGC);
 129 }
 130 
 131 void ShenandoahCodeRoots::add_nmethod(nmethod* nm) {
 132   switch (ShenandoahCodeRootsStyle) {
 133     case 0:
 134     case 1:
 135       break;
 136     case 2: {
 137       assert_locked_or_safepoint(CodeCache_lock);
 138       ShenandoahLocker locker(CodeCache_lock->owned_by_self() ? NULL : &_recorded_nms_lock);
 139 
 140       ShenandoahNMethodOopDetector detector;
 141       nm->oops_do(&detector);
 142 
 143       if (detector.has_oops()) {
 144         ShenandoahNMethod* nmr = new ShenandoahNMethod(nm, detector.oops());
 145         nmr->assert_alive_and_correct();
 146         int idx = _recorded_nms->find(nm, ShenandoahNMethod::find_with_nmethod);
 147         if (idx != -1) {
 148           ShenandoahNMethod* old = _recorded_nms->at(idx);
 149           _recorded_nms->at_put(idx, nmr);
 150           delete old;
 151         } else {
 152           _recorded_nms->append(nmr);
 153         }
 154       }
 155       break;
 156     }
 157     default:
 158       ShouldNotReachHere();
 159   }
 160 };
 161 
 162 void ShenandoahCodeRoots::remove_nmethod(nmethod* nm) {
 163   switch (ShenandoahCodeRootsStyle) {
 164     case 0:
 165     case 1: {
 166       break;
 167     }
 168     case 2: {
 169       assert_locked_or_safepoint(CodeCache_lock);
 170       ShenandoahLocker locker(CodeCache_lock->owned_by_self() ? NULL : &_recorded_nms_lock);
 171 
 172       ShenandoahNMethodOopDetector detector;
 173       nm->oops_do(&detector, /* allow_dead = */ true);
 174 
 175       if (detector.has_oops()) {
 176         int idx = _recorded_nms->find(nm, ShenandoahNMethod::find_with_nmethod);
 177         assert(idx != -1, "nmethod " PTR_FORMAT " should be registered", p2i(nm));
 178         ShenandoahNMethod* old = _recorded_nms->at(idx);
 179         old->assert_same_oops(detector.oops());
 180         _recorded_nms->delete_at(idx);
 181         delete old;
 182       }
 183       break;
 184     }
 185     default:
 186       ShouldNotReachHere();
 187   }
 188 }
 189 
 190 ShenandoahCodeRootsIterator::ShenandoahCodeRootsIterator() :
 191         _heap(ShenandoahHeap::heap()),
 192         _par_iterator(CodeCache::heaps()),
 193         _claimed(0) {
 194   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
 195   assert(!Thread::current()->is_Worker_thread(), "Should not be acquired by workers");
 196   switch (ShenandoahCodeRootsStyle) {
 197     case 0:
 198     case 1: {
 199       // No need to do anything here
 200       break;
 201     }
 202     case 2: {
 203       CodeCache_lock->lock_without_safepoint_check();
 204       break;
 205     }
 206     default:
 207       ShouldNotReachHere();
 208   }
 209 }
 210 
 211 ShenandoahCodeRootsIterator::~ShenandoahCodeRootsIterator() {
 212   switch (ShenandoahCodeRootsStyle) {
 213     case 0:
 214     case 1: {
 215       // No need to do anything here
 216       break;
 217     }
 218     case 2: {
 219       CodeCache_lock->unlock();
 220       break;
 221     }
 222     default:
 223       ShouldNotReachHere();
 224   }
 225 }
 226 
 227 template<bool CSET_FILTER>
 228 void ShenandoahCodeRootsIterator::dispatch_parallel_blobs_do(CodeBlobClosure *f) {
 229   switch (ShenandoahCodeRootsStyle) {
 230     case 0: {
 231       if (_seq_claimed.try_set()) {
 232         CodeCache::blobs_do(f);
 233       }
 234       break;
 235     }
 236     case 1: {
 237       _par_iterator.parallel_blobs_do(f);
 238       break;
 239     }
 240     case 2: {
 241       ShenandoahCodeRootsIterator::fast_parallel_blobs_do<CSET_FILTER>(f);
 242       break;
 243     }
 244     default:
 245       ShouldNotReachHere();
 246   }
 247 }
 248 
 249 void ShenandoahAllCodeRootsIterator::possibly_parallel_blobs_do(CodeBlobClosure *f) {
 250   ShenandoahCodeRootsIterator::dispatch_parallel_blobs_do<false>(f);
 251 }
 252 
 253 void ShenandoahCsetCodeRootsIterator::possibly_parallel_blobs_do(CodeBlobClosure *f) {
 254   ShenandoahCodeRootsIterator::dispatch_parallel_blobs_do<true>(f);
 255 }
 256 
 257 template <bool CSET_FILTER>
 258 void ShenandoahCodeRootsIterator::fast_parallel_blobs_do(CodeBlobClosure *f) {
 259   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
 260 
 261   size_t stride = 256; // educated guess
 262 
 263   GrowableArray<ShenandoahNMethod*>* list = ShenandoahCodeRoots::_recorded_nms;
 264 
 265   size_t max = (size_t)list->length();
 266   while (_claimed < max) {
 267     size_t cur = Atomic::add(&_claimed, stride) - stride;
 268     size_t start = cur;
 269     size_t end = MIN2(cur + stride, max);
 270     if (start >= max) break;
 271 
 272     for (size_t idx = start; idx < end; idx++) {
 273       ShenandoahNMethod* nmr = list->at((int) idx);
 274       nmr->assert_alive_and_correct();
 275 
 276       if (CSET_FILTER && !nmr->has_cset_oops(_heap)) {
 277         continue;
 278       }
 279 
 280       f->do_code_blob(nmr->nm());
 281     }
 282   }
 283 }
 284 
 285 ShenandoahNMethod::ShenandoahNMethod(nmethod* nm, GrowableArray<oop*>* oops) {
 286   _nm = nm;
 287   _oops = NEW_C_HEAP_ARRAY(oop*, oops->length(), mtGC);
 288   _oops_count = oops->length();
 289   for (int c = 0; c < _oops_count; c++) {
 290     _oops[c] = oops->at(c);
 291   }
 292 }
 293 
 294 ShenandoahNMethod::~ShenandoahNMethod() {
 295   if (_oops != NULL) {
 296     FREE_C_HEAP_ARRAY(oop*, _oops);
 297   }
 298 }
 299 
 300 bool ShenandoahNMethod::has_cset_oops(ShenandoahHeap *heap) {
 301   for (int c = 0; c < _oops_count; c++) {
 302     oop o = RawAccess<>::oop_load(_oops[c]);
 303     if (heap->in_collection_set(o)) {
 304       return true;
 305     }
 306   }
 307   return false;
 308 }
 309 
 310 #ifdef ASSERT
 311 void ShenandoahNMethod::assert_alive_and_correct() {
 312   assert(_nm->is_alive(), "only alive nmethods here");
 313   assert(_oops_count > 0, "should have filtered nmethods without oops before");
 314   ShenandoahHeap* heap = ShenandoahHeap::heap();
 315   for (int c = 0; c < _oops_count; c++) {
 316     oop *loc = _oops[c];
 317     assert(_nm->code_contains((address) loc) || _nm->oops_contains(loc), "nmethod should contain the oop*");
 318     oop o = RawAccess<>::oop_load(loc);
 319     shenandoah_assert_correct_except(loc, o,
 320              o == NULL ||
 321              heap->is_full_gc_move_in_progress() ||
 322              (VMThread::vm_operation() != NULL) && (VMThread::vm_operation()->type() == VM_Operation::VMOp_HeapWalkOperation)
 323     );
 324   }
 325 }
 326 
 327 void ShenandoahNMethod::assert_same_oops(GrowableArray<oop*>* oops) {
 328   assert(_oops_count == oops->length(), "should have the same number of oop*");
 329   for (int c = 0; c < _oops_count; c++) {
 330     assert(_oops[c] == oops->at(c), "should be the same oop*");
 331   }
 332 }
 333 #endif