/*

 * Copyright (c) 1997, 2014, 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.inline.hpp"

#include "runtime/compilationPolicy.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/orderAccess.inline.hpp"

#include "runtime/os.hpp"

#include "runtime/sweeper.hpp"

#include "runtime/thread.inline.hpp"

#include "runtime/vm_operations.hpp"

#include "trace/tracing.hpp"

#include "utilities/events.hpp"

#include "utilities/ticks.inline.hpp"

#include "utilities/xmlstream.hpp"

PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC

#ifdef ASSERT

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

// Sweeper logging code

class SweeperRecord {

 public:

  int traversal;

  int compile_id;

  long traversal_mark;

  int state;

  const char* kind;

  address vep;

  address uep;

  int line;

  void print() {

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

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

                    traversal,

                    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].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;

  }

}

void NMethodSweeper::init_sweeper_log() {

 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);

  }

}

#else

#define SWEEP(nm)

#endif

NMethodIterator NMethodSweeper::_current;                      // Current nmethod

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

long     NMethodSweeper::_total_nof_code_cache_sweeps  = 0;    // Total number of full sweeps of the code cache

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::_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::_hotness_counter_reset_val       = 0;

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

long   NMethodSweeper::_total_nof_c2_methods_reclaimed  = 0;   // Accumulated nof methods flushed

size_t NMethodSweeper::_total_flushed_size              = 0;   // Total number of bytes flushed from the code cache

Tickspan NMethodSweeper::_total_time_sweeping;                 // Accumulated time sweeping

Tickspan NMethodSweeper::_total_time_this_sweep;               // Total time this sweep

Tickspan NMethodSweeper::_peak_sweep_time;                     // Peak time for a full sweep

Tickspan NMethodSweeper::_peak_sweep_fraction_time;            // Peak time sweeping one fraction

class MarkActivationClosure: public CodeBlobClosure {

public:

  virtual void do_code_blob(CodeBlob* cb) {

    assert(cb->is_nmethod(), "CodeBlob should be 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) {

    assert(cb->is_nmethod(), "CodeBlob should be 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::wait_for_stack_scanning() {

  return _current.end();

}

/**

  * 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.method()) == _current.method(), "Sweeper nmethod cached state invalid");

  if (wait_for_stack_scanning()) {

    _seen = 0;

    _current = NMethodIterator();

    // Initialize to first nmethod

    _current.next();

    _traversals += 1;

    _total_time_this_sweep = Tickspan();

    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 triggers a VM operation that does stack scanning of active

  * methods. Stack scanning is mandatory for the sweeper to make progress.

  */

void NMethodSweeper::do_stack_scanning() {

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

  if (wait_for_stack_scanning()) {

    VM_MarkActiveNMethods op;

    VMThread::execute(&op);

    _should_sweep = true;

  }

}

void NMethodSweeper::sweeper_loop() {

  bool timeout;

  while (true) {

    {

      ThreadBlockInVM tbivm(JavaThread::current());

      MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);

      const long wait_time = 60*60*24 * 1000;

      timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time);

    }

    if (!timeout) {

      possibly_sweep();

    }

  }

}

/**

  * Wakes up the sweeper thread to possibly sweep.

  */

void NMethodSweeper::notify(int code_blob_type) {

  // Makes sure that we do not invoke the sweeper too often during startup.

  double start_threshold = 100.0 / (double)StartAggressiveSweepingAt;

  double aggressive_sweep_threshold = MIN2(start_threshold, 1.1);

  if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) {

    assert_locked_or_safepoint(CodeCache_lock);

    CodeCache_lock->notify();

  }

}

/**

 * Handle a safepoint request

 */

void NMethodSweeper::handle_safepoint_request() {

  if (SafepointSynchronize::is_synchronizing()) {

    if (PrintMethodFlushing && Verbose) {

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

    }

    MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

    JavaThread* thread = JavaThread::current();

    ThreadBlockInVM tbivm(thread);

    thread->java_suspend_self();

  }

}

/**

 * 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");

  // 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) {

    const int time_since_last_sweep = _time_counter - _last_sweep;

    // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,

    // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using

    // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive

    // value) that disables the intended periodic sweeps.

    const int max_wait_time = ReservedCodeCacheSize / (16 * M);

    double wait_until_next_sweep = max_wait_time - time_since_last_sweep -

        MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),

             CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));

    assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");

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

      _should_sweep = true;

    }

  }

  // Force stack scanning if there is only 10% free space in the code cache.

  // We force stack scanning only non-profiled code heap gets full, since critical

  // allocation go to the non-profiled heap and we must be make sure that there is

  // enough space.

  double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100;

  if (free_percent <= StartAggressiveSweepingAt) {

    do_stack_scanning();

  }

  if (_should_sweep) {

    init_sweeper_log();

    sweep_code_cache();

  }

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

  _total_nof_code_cache_sweeps++;

  _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;

  }

}

void NMethodSweeper::sweep_code_cache() {

  ResourceMark rm;

  Ticks sweep_start_counter = Ticks::now();

  _flushed_count                = 0;

  _zombified_count              = 0;

  _marked_for_reclamation_count = 0;

  if (PrintMethodFlushing && Verbose) {

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

  }

  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

    while (!_current.end()) {

      swept_count++;

      handle_safepoint_request();

      // 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* nm = _current.method();

      _current.next();

      // Now ready to process nmethod and give up CodeCache_lock

      {

        MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

        freed_memory += process_nmethod(nm);

      }

      _seen++;

    }

  }

  assert(_current.end(), "must have scanned the whole cache");

  const Ticks sweep_end_counter = Ticks::now();

  const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;

  _total_time_sweeping  += sweep_time;

  _total_time_this_sweep += sweep_time;

  _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);

  _total_flushed_size += freed_memory;

  _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_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) {

    tty->print_cr("### sweeper:      sweep time(%d): ", (jlong)sweep_time.value());

  }

#endif

  _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:

  CodeCacheSweeperThread* _thread;

 public:

  NMethodMarker(nmethod* nm) {

    JavaThread* current = JavaThread::current();

    assert (current->is_Code_cache_sweeper_thread(), "Must be");

    _thread = (CodeCacheSweeperThread*)JavaThread::current();

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

      // Only expose live nmethods for scanning

      _thread->set_scanned_nmethod(nm);