Java example source code file (jvmtiCodeBlobEvents.cpp)

This example Java source code file (jvmtiCodeBlobEvents.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

codeblobcollector, codecache\:\:next_nmethod, growablearray, invocationentrybci, jvmti_error_none, jvmticodeblobdesc, jvmticodeblobevents\:\:build_jvmti_addr_location_map, mutex\:\:_no_safepoint_check_flag, mutexlockerex, mutexunlockerex, new_c_heap_array, null, resourceobj\:\:c_heap, scopedesc

The jvmtiCodeBlobEvents.cpp Java example source code

/*
 * Copyright (c) 2003, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "code/codeBlob.hpp"
#include "code/codeCache.hpp"
#include "code/scopeDesc.hpp"
#include "memory/resourceArea.hpp"
#include "oops/oop.inline.hpp"
#include "prims/jvmtiCodeBlobEvents.hpp"
#include "prims/jvmtiExport.hpp"
#include "runtime/handles.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/vmThread.hpp"

// Support class to collect a list of the non-nmethod CodeBlobs in
// the CodeCache.
//
// This class actually creates a list of JvmtiCodeBlobDesc - each JvmtiCodeBlobDesc
// describes a single CodeBlob in the CodeCache. Note that collection is
// done to a static list - this is because CodeCache::blobs_do is defined
// as void CodeCache::blobs_do(void f(CodeBlob* nm)) and hence requires
// a C or static method.
//
// Usage :-
//
// CodeBlobCollector collector;
//
// collector.collect();
// JvmtiCodeBlobDesc* blob = collector.first();
// while (blob != NULL) {
//   :
//   blob = collector.next();
// }
//

class CodeBlobCollector : StackObj {
 private:
  GrowableArray<JvmtiCodeBlobDesc*>* _code_blobs;   // collected blobs
  int _pos;                                         // iterator position

  // used during a collection
  static GrowableArray<JvmtiCodeBlobDesc*>* _global_code_blobs;
  static void do_blob(CodeBlob* cb);
 public:
  CodeBlobCollector() {
    _code_blobs = NULL;
    _pos = -1;
  }
  ~CodeBlobCollector() {
    if (_code_blobs != NULL) {
      for (int i=0; i<_code_blobs->length(); i++) {
        FreeHeap(_code_blobs->at(i));
      }
      delete _code_blobs;
    }
  }

  // collect list of code blobs in the cache
  void collect();

  // iteration support - return first code blob
  JvmtiCodeBlobDesc* first() {
    assert(_code_blobs != NULL, "not collected");
    if (_code_blobs->length() == 0) {
      return NULL;
    }
    _pos = 0;
    return _code_blobs->at(0);
  }

  // iteration support - return next code blob
  JvmtiCodeBlobDesc* next() {
    assert(_pos >= 0, "iteration not started");
    if (_pos+1 >= _code_blobs->length()) {
      return NULL;
    }
    return _code_blobs->at(++_pos);
  }

};

// used during collection
GrowableArray<JvmtiCodeBlobDesc*>* CodeBlobCollector::_global_code_blobs;


// called for each CodeBlob in the CodeCache
//
// This function filters out nmethods as it is only interested in
// other CodeBlobs. This function also filters out CodeBlobs that have
// a duplicate starting address as previous blobs. This is needed to
// handle the case where multiple stubs are generated into a single
// BufferBlob.

void CodeBlobCollector::do_blob(CodeBlob* cb) {

  // ignore nmethods
  if (cb->is_nmethod()) {
    return;
  }

  // check if this starting address has been seen already - the
  // assumption is that stubs are inserted into the list before the
  // enclosing BufferBlobs.
  address addr = cb->code_begin();
  for (int i=0; i<_global_code_blobs->length(); i++) {
    JvmtiCodeBlobDesc* scb = _global_code_blobs->at(i);
    if (addr == scb->code_begin()) {
      return;
    }
  }

  // record the CodeBlob details as a JvmtiCodeBlobDesc
  JvmtiCodeBlobDesc* scb = new JvmtiCodeBlobDesc(cb->name(), cb->code_begin(), cb->code_end());
  _global_code_blobs->append(scb);
}


// collects a list of CodeBlobs in the CodeCache.
//
// The created list is growable array of JvmtiCodeBlobDesc - each one describes
// a CodeBlob. Note that the list is static - this is because CodeBlob::blobs_do
// requires a a C or static function so we can't use an instance function. This
// isn't a problem as the iteration is serial anyway as we need the CodeCache_lock
// to iterate over the code cache.
//
// Note that the CodeBlobs in the CodeCache will include BufferBlobs that may
// contain multiple stubs. As a profiler is interested in the stubs rather than
// the enclosing container we first iterate over the stub code descriptors so
// that the stubs go into the list first. do_blob will then filter out the
// enclosing blobs if the starting address of the enclosing blobs matches the
// starting address of first stub generated in the enclosing blob.

void CodeBlobCollector::collect() {
  assert_locked_or_safepoint(CodeCache_lock);
  assert(_global_code_blobs == NULL, "checking");

  // create the global list
  _global_code_blobs = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<JvmtiCodeBlobDesc*>(50,true);

  // iterate over the stub code descriptors and put them in the list first.
  int index = 0;
  StubCodeDesc* desc;
  while ((desc = StubCodeDesc::desc_for_index(++index)) != NULL) {
    _global_code_blobs->append(new JvmtiCodeBlobDesc(desc->name(), desc->begin(), desc->end()));
  }

  // next iterate over all the non-nmethod code blobs and add them to
  // the list - as noted above this will filter out duplicates and
  // enclosing blobs.
  CodeCache::blobs_do(do_blob);

  // make the global list the instance list so that it can be used
  // for other iterations.
  _code_blobs = _global_code_blobs;
  _global_code_blobs = NULL;
}


// Generate a DYNAMIC_CODE_GENERATED event for each non-nmethod code blob.

jvmtiError JvmtiCodeBlobEvents::generate_dynamic_code_events(JvmtiEnv* env) {
  CodeBlobCollector collector;

  // First collect all the code blobs.  This has to be done in a
  // single pass over the code cache with CodeCache_lock held because
  // there isn't any safe way to iterate over regular CodeBlobs since
  // they can be freed at any point.
  {
    MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
    collector.collect();
  }

  // iterate over the collected list and post an event for each blob
  JvmtiCodeBlobDesc* blob = collector.first();
  while (blob != NULL) {
    JvmtiExport::post_dynamic_code_generated(env, blob->name(), blob->code_begin(), blob->code_end());
    blob = collector.next();
  }
  return JVMTI_ERROR_NONE;
}


// Generate a COMPILED_METHOD_LOAD event for each nnmethod
jvmtiError JvmtiCodeBlobEvents::generate_compiled_method_load_events(JvmtiEnv* env) {
  HandleMark hm;

  // Walk the CodeCache notifying for live nmethods.  The code cache
  // may be changing while this is happening which is ok since newly
  // created nmethod will notify normally and nmethods which are freed
  // can be safely skipped.
  MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
  nmethod* current = CodeCache::first_nmethod();
  while (current != NULL) {
    // Only notify for live nmethods
    if (current->is_alive()) {
      // Lock the nmethod so it can't be freed
      nmethodLocker nml(current);

      // Don't hold the lock over the notify or jmethodID creation
      MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
      current->get_and_cache_jmethod_id();
      JvmtiExport::post_compiled_method_load(current);
    }
    current = CodeCache::next_nmethod(current);
  }
  return JVMTI_ERROR_NONE;
}


// create a C-heap allocated address location map for an nmethod
void JvmtiCodeBlobEvents::build_jvmti_addr_location_map(nmethod *nm,
                                                        jvmtiAddrLocationMap** map_ptr,
                                                        jint *map_length_ptr)
{
  ResourceMark rm;
  jvmtiAddrLocationMap* map = NULL;
  jint map_length = 0;


  // Generate line numbers using PcDesc and ScopeDesc info
  methodHandle mh(nm->method());

  if (!mh->is_native()) {
    PcDesc *pcd;
    int pcds_in_method;

    pcds_in_method = (nm->scopes_pcs_end() - nm->scopes_pcs_begin());
    map = NEW_C_HEAP_ARRAY(jvmtiAddrLocationMap, pcds_in_method, mtInternal);

    address scopes_data = nm->scopes_data_begin();
    for( pcd = nm->scopes_pcs_begin(); pcd < nm->scopes_pcs_end(); ++pcd ) {
      ScopeDesc sc0(nm, pcd->scope_decode_offset(), pcd->should_reexecute(), pcd->return_oop());
      ScopeDesc *sd  = &sc0;
      while( !sd->is_top() ) { sd = sd->sender(); }
      int bci = sd->bci();
      if (bci != InvocationEntryBci) {
        assert(map_length < pcds_in_method, "checking");
        map[map_length].start_address = (const void*)pcd->real_pc(nm);
        map[map_length].location = bci;
        ++map_length;
      }
    }
  }

  *map_ptr = map;
  *map_length_ptr = map_length;
}