/*

 * Copyright (c) 1997, 2013, 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/codeCache.hpp"

#include "code/compiledIC.hpp"

#include "code/icBuffer.hpp"

#include "code/nmethod.hpp"

#include "compiler/compileBroker.hpp"

#include "memory/resourceArea.hpp"

#include "oops/method.hpp"

#include "runtime/atomic.hpp"

#include "runtime/compilationPolicy.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/os.hpp"

#include "runtime/sweeper.hpp"

#include "runtime/vm_operations.hpp"

#include "trace/tracing.hpp"

#include "utilities/events.hpp"

#include "utilities/xmlstream.hpp"

#ifdef ASSERT

#define SWEEP(nm) record_sweep(nm, __LINE__)

// Sweeper logging code

class SweeperRecord {

 public:

  int traversal;

  int invocation;

  int compile_id;

  long traversal_mark;

  int state;

  const char* kind;

  address vep;

  address uep;

  int line;

  void print() {

      tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "

                    PTR_FORMAT " state = %d traversal_mark %d line = %d",

                    traversal,

                    invocation,

                    compile_id,

                    kind == NULL ? "" : kind,

                    uep,

                    vep,

                    state,

                    traversal_mark,

                    line);

  }

};

static int _sweep_index = 0;

static SweeperRecord* _records = NULL;

void NMethodSweeper::report_events(int id, address entry) {

  if (_records != NULL) {

    for (int i = _sweep_index; i < SweeperLogEntries; i++) {

      if (_records[i].uep == entry ||

          _records[i].vep == entry ||

          _records[i].compile_id == id) {

        _records[i].print();

      }

    }

    for (int i = 0; i < _sweep_index; i++) {

      if (_records[i].uep == entry ||

          _records[i].vep == entry ||

          _records[i].compile_id == id) {

        _records[i].print();

      }

    }

  }

}

void NMethodSweeper::report_events() {

  if (_records != NULL) {

    for (int i = _sweep_index; i < SweeperLogEntries; i++) {

      // skip empty records

      if (_records[i].vep == NULL) continue;

      _records[i].print();

    }

    for (int i = 0; i < _sweep_index; i++) {

      // skip empty records

      if (_records[i].vep == NULL) continue;

      _records[i].print();

    }

  }

}

void NMethodSweeper::record_sweep(nmethod* nm, int line) {

  if (_records != NULL) {

    _records[_sweep_index].traversal = _traversals;

    _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;

    _records[_sweep_index].invocation = _sweep_fractions_left;

    _records[_sweep_index].compile_id = nm->compile_id();

    _records[_sweep_index].kind = nm->compile_kind();

    _records[_sweep_index].state = nm->_state;

    _records[_sweep_index].vep = nm->verified_entry_point();

    _records[_sweep_index].uep = nm->entry_point();

    _records[_sweep_index].line = line;

    _sweep_index = (_sweep_index + 1) % SweeperLogEntries;

  }

}

#else

#define SWEEP(nm)

#endif

nmethod* NMethodSweeper::_current                      = NULL; // Current nmethod

long     NMethodSweeper::_traversals                   = 0;    // Stack scan count, also sweep ID.

long     NMethodSweeper::_time_counter                 = 0;    // Virtual time used to periodically invoke sweeper

long     NMethodSweeper::_last_sweep                   = 0;    // Value of _time_counter when the last sweep happened

int      NMethodSweeper::_seen                         = 0;    // Nof. nmethod we have currently processed in current pass of CodeCache

int      NMethodSweeper::_flushed_count                = 0;    // Nof. nmethods flushed in current sweep

int      NMethodSweeper::_zombified_count              = 0;    // Nof. nmethods made zombie in current sweep

int      NMethodSweeper::_marked_for_reclamation_count = 0;    // Nof. nmethods marked for reclaim in current sweep

volatile bool NMethodSweeper::_should_sweep            = true; // Indicates if we should invoke the sweeper

volatile int  NMethodSweeper::_sweep_fractions_left    = 0;    // Nof. invocations left until we are completed with this pass

volatile int  NMethodSweeper::_sweep_started           = 0;    // Flag to control conc sweeper

volatile int  NMethodSweeper::_bytes_changed           = 0;    // Counts the total nmethod size if the nmethod changed from:

                                                               //   1) alive       -> not_entrant

                                                               //   2) not_entrant -> zombie

                                                               //   3) zombie      -> marked_for_reclamation

int   NMethodSweeper::_total_nof_methods_reclaimed     = 0;    // Accumulated nof methods flushed

int   NMethodSweeper::_hotness_counter_reset_val       = 0;

class MarkActivationClosure: public CodeBlobClosure {

public:

  virtual void do_code_blob(CodeBlob* cb) {

    if (cb->is_nmethod()) {

      nmethod* nm = (nmethod*)cb;

      nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());

      // If we see an activation belonging to a non_entrant nmethod, we mark it.

      if (nm->is_not_entrant()) {

        nm->mark_as_seen_on_stack();

      }

    }

  }

};

static MarkActivationClosure mark_activation_closure;

class SetHotnessClosure: public CodeBlobClosure {

public:

  virtual void do_code_blob(CodeBlob* cb) {

    if (cb->is_nmethod()) {

      nmethod* nm = (nmethod*)cb;

      nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());

    }

  }

};

static SetHotnessClosure set_hotness_closure;

int NMethodSweeper::hotness_counter_reset_val() {

  if (_hotness_counter_reset_val == 0) {

    _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;

  }

  return _hotness_counter_reset_val;

}

bool NMethodSweeper::sweep_in_progress() {

  return (_current != NULL);

}

// Scans the stacks of all Java threads and marks activations of not-entrant methods.

// No need to synchronize access, since 'mark_active_nmethods' is always executed at a

// safepoint.

void NMethodSweeper::mark_active_nmethods() {

  assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");

  // If we do not want to reclaim not-entrant or zombie methods there is no need

  // to scan stacks

  if (!MethodFlushing) {

    return;

  }

  // Increase time so that we can estimate when to invoke the sweeper again.

  _time_counter++;

  // Check for restart

  assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");

  if (!sweep_in_progress()) {

    _seen = 0;

    _sweep_fractions_left = NmethodSweepFraction;

    _current = CodeCache::first_nmethod();

    _traversals += 1;

    if (PrintMethodFlushing) {

      tty->print_cr("### Sweep: stack traversal %d", _traversals);

    }

    Threads::nmethods_do(&mark_activation_closure);

  } else {

    // Only set hotness counter

    Threads::nmethods_do(&set_hotness_closure);

  }

  OrderAccess::storestore();

}

/**

 * This function invokes the sweeper if at least one of the three conditions is met:

 *    (1) The code cache is getting full

 *    (2) There are sufficient state changes in/since the last sweep.

 *    (3) We have not been sweeping for 'some time'

 */

void NMethodSweeper::possibly_sweep() {

  assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");

  // Only compiler threads are allowed to sweep

  if (!MethodFlushing || !sweep_in_progress() || !Thread::current()->is_Compiler_thread()) {

    return;

  }

  // If there was no state change while nmethod sweeping, 'should_sweep' will be false.

  // This is one of the two places where should_sweep can be set to true. The general

  // idea is as follows: If there is enough free space in the code cache, there is no

  // need to invoke the sweeper. The following formula (which determines whether to invoke

  // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes

  // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,

  // the formula considers how much space in the code cache is currently used. Here are

  // some examples that will (hopefully) help in understanding.

  //

  // Small ReservedCodeCacheSizes:  (e.g., < 16M) We invoke the sweeper every time, since

  //                                              the result of the division is 0. This

  //                                              keeps the used code cache size small

  //                                              (important for embedded Java)

  // Large ReservedCodeCacheSize :  (e.g., 256M + code cache is 10% full). The formula

  //                                              computes: (256 / 16) - 1 = 15

  //                                              As a result, we invoke the sweeper after

  //                                              15 invocations of 'mark_active_nmethods.

  // Large ReservedCodeCacheSize:   (e.g., 256M + code Cache is 90% full). The formula

  //                                              computes: (256 / 16) - 10 = 6.

  if (!_should_sweep) {

    int time_since_last_sweep = _time_counter - _last_sweep;

    double wait_until_next_sweep = (ReservedCodeCacheSize / (16 * M)) - time_since_last_sweep -

                                CodeCache::reverse_free_ratio();

    if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {

      _should_sweep = true;

    }

  }

  if (_should_sweep && _sweep_fractions_left > 0) {

    // Only one thread at a time will sweep

    jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );

    if (old != 0) {

      return;

    }

#ifdef ASSERT

    if (LogSweeper && _records == NULL) {

      // Create the ring buffer for the logging code

      _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);

      memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);

    }

#endif

    if (_sweep_fractions_left > 0) {

      sweep_code_cache();

      _sweep_fractions_left--;

    }

    // We are done with sweeping the code cache once.

    if (_sweep_fractions_left == 0) {

      _last_sweep = _time_counter;

      // Reset flag; temporarily disables sweeper

      _should_sweep = false;

      // If there was enough state change, 'possibly_enable_sweeper()'

      // sets '_should_sweep' to true

      possibly_enable_sweeper();

      // Reset _bytes_changed only if there was enough state change. _bytes_changed

      // can further increase by calls to 'report_state_change'.

      if (_should_sweep) {

        _bytes_changed = 0;

      }

    }

    _sweep_started = 0;

  }

}

void NMethodSweeper::sweep_code_cache() {

  _flushed_count                = 0;

  _zombified_count              = 0;

  _marked_for_reclamation_count = 0;

  if (PrintMethodFlushing && Verbose) {

    tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);

  }

  if (!CompileBroker::should_compile_new_jobs()) {

    // If we have turned off compilations we might as well do full sweeps

    // in order to reach the clean state faster. Otherwise the sleeping compiler

    // threads will slow down sweeping.

    _sweep_fractions_left = 1;

  }

  // We want to visit all nmethods after NmethodSweepFraction

  // invocations so divide the remaining number of nmethods by the

  // remaining number of invocations.  This is only an estimate since

  // the number of nmethods changes during the sweep so the final

  // stage must iterate until it there are no more nmethods.

  int todo = (CodeCache::nof_nmethods() - _seen) / _sweep_fractions_left;

  int swept_count = 0;

  assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");

  assert(!CodeCache_lock->owned_by_self(), "just checking");

  int freed_memory = 0;

  {

    MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

    // The last invocation iterates until there are no more nmethods

    for (int i = 0; (i < todo || _sweep_fractions_left == 1) && _current != NULL; i++) {

      swept_count++;

      if (SafepointSynchronize::is_synchronizing()) { // Safepoint request

        if (PrintMethodFlushing && Verbose) {

          tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);

        }

        MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

        assert(Thread::current()->is_Java_thread(), "should be java thread");

        JavaThread* thread = (JavaThread*)Thread::current();

        ThreadBlockInVM tbivm(thread);

        thread->java_suspend_self();

      }

      // Since we will give up the CodeCache_lock, always skip ahead

      // to the next nmethod.  Other blobs can be deleted by other

      // threads but nmethods are only reclaimed by the sweeper.

      nmethod* next = CodeCache::next_nmethod(_current);

      // Now ready to process nmethod and give up CodeCache_lock

      {

        MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

        freed_memory += process_nmethod(_current);

      }

      _seen++;

      _current = next;

    }

  }

  assert(_sweep_fractions_left > 1 || _current == NULL, "must have scanned the whole cache");

  _total_time_sweeping  += sweep_time;

  _total_time_this_sweep += sweep_time;

  _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);

  _total_nof_methods_reclaimed += _flushed_count;

  EventSweepCodeCache event(UNTIMED);

  if (event.should_commit()) {

    event.set_starttime(sweep_start_counter);

    event.set_endtime(sweep_end_counter);

    event.set_sweepIndex(_traversals);

    event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);

    event.set_sweptCount(swept_count);

    event.set_flushedCount(_flushed_count);

    event.set_markedCount(_marked_for_reclamation_count);

    event.set_zombifiedCount(_zombified_count);

    event.commit();

  }

#ifdef ASSERT

  if(PrintMethodFlushing) {

  }

#endif

  if (_sweep_fractions_left == 1) {

    _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);

    log_sweep("finished");

  }

  // Sweeper is the only case where memory is released, check here if it

  // is time to restart the compiler. Only checking if there is a certain

  // amount of free memory in the code cache might lead to re-enabling

  // compilation although no memory has been released. For example, there are

  // cases when compilation was disabled although there is 4MB (or more) free

  // memory in the code cache. The reason is code cache fragmentation. Therefore,

  // it only makes sense to re-enable compilation if we have actually freed memory.

  // Note that typically several kB are released for sweeping 16MB of the code

  // cache. As a result, 'freed_memory' > 0 to restart the compiler.

  if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {

    CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);

    log_sweep("restart_compiler");

  }

}

/**

 * This function updates the sweeper statistics that keep track of nmethods

 * state changes. If there is 'enough' state change, the sweeper is invoked

 * as soon as possible. There can be data races on _bytes_changed. The data

 * races are benign, since it does not matter if we loose a couple of bytes.

 * In the worst case we call the sweeper a little later. Also, we are guaranteed

 * to invoke the sweeper if the code cache gets full.

 */

void NMethodSweeper::report_state_change(nmethod* nm) {

  _bytes_changed += nm->total_size();

  possibly_enable_sweeper();

}

/**

 * Function determines if there was 'enough' state change in the code cache to invoke

 * the sweeper again. Currently, we determine 'enough' as more than 1% state change in

 * the code cache since the last sweep.

 */

void NMethodSweeper::possibly_enable_sweeper() {

  double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;

  if (percent_changed > 1.0) {

    _should_sweep = true;

  }

}

class NMethodMarker: public StackObj {

 private:

  CompilerThread* _thread;

 public:

  NMethodMarker(nmethod* nm) {

    _thread = CompilerThread::current();

    if (!nm->is_zombie() && !nm->is_unloaded()) {

      // Only expose live nmethods for scanning

      _thread->set_scanned_nmethod(nm);

    }

  }

  ~NMethodMarker() {

    _thread->set_scanned_nmethod(NULL);

  }

};

void NMethodSweeper::release_nmethod(nmethod *nm) {

  // Clean up any CompiledICHolders

  {

    ResourceMark rm;

    MutexLocker ml_patch(CompiledIC_lock);

    RelocIterator iter(nm);

    while (iter.next()) {

      if (iter.type() == relocInfo::virtual_call_type) {

        CompiledIC::cleanup_call_site(iter.virtual_call_reloc());

      }

    }

  }

  MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

  nm->flush();

}

int NMethodSweeper::process_nmethod(nmethod *nm) {

  assert(!CodeCache_lock->owned_by_self(), "just checking");

  int freed_memory = 0;

  // Make sure this nmethod doesn't get unloaded during the scan,

  // since safepoints may happen during acquired below locks.

  NMethodMarker nmm(nm);

  SWEEP(nm);

  // Skip methods that are currently referenced by the VM

  if (nm->is_locked_by_vm()) {

    // But still remember to clean-up inline caches for alive nmethods

    if (nm->is_alive()) {

      // Clean inline caches that point to zombie/non-entrant methods