/*

 * 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 = _invocations;

    _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

long      NMethodSweeper::_traversals = 0;   // No. of stack traversals performed

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

int       NMethodSweeper::_seen = 0 ;        // No. of nmethods 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_count = 0;    // Nof. nmethods marked for reclaim in current sweep

volatile int NMethodSweeper::_invocations = 0;   // No. of invocations left until we are completed with this pass

volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.

jint      NMethodSweeper::_locked_seen = 0;

jint      NMethodSweeper::_not_entrant_seen_on_stack = 0;

bool      NMethodSweeper::_resweep = false;

jint      NMethodSweeper::_flush_token = 0;

jlong     NMethodSweeper::_last_full_flush_time = 0;

int       NMethodSweeper::_highest_marked = 0;

int       NMethodSweeper::_dead_compile_ids = 0;

long      NMethodSweeper::_last_flush_traversal_id = 0;

int       NMethodSweeper::_number_of_flushes = 0; // Total of full traversals caused by full cache

int       NMethodSweeper::_total_nof_methods_reclaimed = 0;

jlong     NMethodSweeper::_total_time_sweeping = 0;

jlong     NMethodSweeper::_total_time_this_sweep = 0;

jlong     NMethodSweeper::_peak_sweep_time = 0;

jlong     NMethodSweeper::_peak_sweep_fraction_time = 0;

jlong     NMethodSweeper::_total_disconnect_time = 0;

jlong     NMethodSweeper::_peak_disconnect_time = 0;

class MarkActivationClosure: public CodeBlobClosure {

public:

  virtual void do_code_blob(CodeBlob* cb) {

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

    if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {

      ((nmethod*)cb)->mark_as_seen_on_stack();

    }

  }

};

static MarkActivationClosure mark_activation_closure;

bool NMethodSweeper::sweep_in_progress() {

  return (_current != NULL);

}

void NMethodSweeper::scan_stacks() {

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

  if (!MethodFlushing) return;

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

  // safepoint.

  // Make sure CompiledIC_lock in unlocked, since we might update some

  // inline caches. If it is, we just bail-out and try later.

  if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;

  // Check for restart

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

  if (!sweep_in_progress() && _resweep) {

    _seen        = 0;

    _invocations = NmethodSweepFraction;

    _current     = CodeCache::first_nmethod();

    _traversals  += 1;

    _total_time_this_sweep = 0;

    if (PrintMethodFlushing) {

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

    }

    Threads::nmethods_do(&mark_activation_closure);

    // reset the flags since we started a scan from the beginning.

    _resweep = false;

    _locked_seen = 0;

    _not_entrant_seen_on_stack = 0;

  }

  if (UseCodeCacheFlushing) {

    // only allow new flushes after the interval is complete.

    jlong now           = os::javaTimeMillis();

    jlong max_interval  = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;

    jlong curr_interval = now - _last_full_flush_time;

    if (curr_interval > max_interval) {

      _flush_token = 0;

    }

    if (!CodeCache::needs_flushing() && !CompileBroker::should_compile_new_jobs()) {

      CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);

      log_sweep("restart_compiler");

    }

  }

}

void NMethodSweeper::possibly_sweep() {

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

  if (!MethodFlushing || !sweep_in_progress()) return;

  if (_invocations > 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 (_invocations > 0) {

      sweep_code_cache();

      _invocations--;

    }

    _sweep_started = 0;

  }

}

void NMethodSweeper::sweep_code_cache() {

  jlong sweep_start_counter = os::elapsed_counter();

  _flushed_count   = 0;

  _zombified_count = 0;

  _marked_count    = 0;

  if (PrintMethodFlushing && Verbose) {

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

  }

  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. After a few iterations the cache

    // will be clean and sweeping stops (_resweep will not be set)

    _invocations = 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) / _invocations;

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

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

  {

    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 || _invocations == 1) && _current != NULL; i++) {

      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(), _invocations);

        }

        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);

        process_nmethod(_current);

      }

      _seen++;

      _current = next;

    }

  }

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

  if (!sweep_in_progress() && !_resweep && (_locked_seen || _not_entrant_seen_on_stack)) {

    // we've completed a scan without making progress but there were

    // nmethods we were unable to process either because they were

    // locked or were still on stack.  We don't have to aggresively

    // clean them up so just stop scanning.  We could scan once more

    // but that complicates the control logic and it's unlikely to

    // matter much.

    if (PrintMethodFlushing) {

      tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");

    }

  }

  jlong sweep_end_counter = os::elapsed_counter();

  jlong 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_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 - _invocations + 1);

    event.set_flushedCount(_flushed_count);

    event.set_markedCount(_marked_count);

    event.set_zombifiedCount(_zombified_count);

    event.commit();

  }

#ifdef ASSERT

  if(PrintMethodFlushing) {

    tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _invocations, (jlong)sweep_time);

  }

#endif

  if (_invocations == 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.

  if (UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs() && !CodeCache::needs_flushing()) {

    CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);

    log_sweep("restart_compiler");

  }

}

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();

}

void NMethodSweeper::process_nmethod(nmethod *nm) {

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

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

  // since the locks acquired below might safepoint.

  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-up all inline caches that points to zombie/non-reentrant methods

      MutexLocker cl(CompiledIC_lock);

      nm->cleanup_inline_caches();

      SWEEP(nm);

    } else {

      _locked_seen++;

      SWEEP(nm);

    }

    return;

  }

  if (nm->is_zombie()) {

    // If it is first time, we see nmethod then we mark it. Otherwise,

    // we reclame it. When we have seen a zombie method twice, we know that

    // there are no inline caches that refer to it.

    if (nm->is_marked_for_reclamation()) {

      assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");

      if (PrintMethodFlushing && Verbose) {

        tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);

      }

      release_nmethod(nm);

      _flushed_count++;

    } else {

      if (PrintMethodFlushing && Verbose) {

        tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);

      }

      nm->mark_for_reclamation();

      _resweep = true;

      _marked_count++;

      SWEEP(nm);

    }

  } else if (nm->is_not_entrant()) {

    // If there is no current activations of this method on the

    // stack we can safely convert it to a zombie method

    if (nm->can_not_entrant_be_converted()) {

      if (PrintMethodFlushing && Verbose) {

        tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);

      }

      nm->make_zombie();

      _resweep = true;

      _zombified_count++;

      SWEEP(nm);

    } else {

      // Still alive, clean up its inline caches

      MutexLocker cl(CompiledIC_lock);

      nm->cleanup_inline_caches();

      // we coudn't transition this nmethod so don't immediately

      // request a rescan.  If this method stays on the stack for a

      // long time we don't want to keep rescanning the code cache.

      _not_entrant_seen_on_stack++;

      SWEEP(nm);

    }

  } else if (nm->is_unloaded()) {

    // Unloaded code, just make it a zombie

    if (PrintMethodFlushing && Verbose)

      tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);

    if (nm->is_osr_method()) {

      SWEEP(nm);

      // No inline caches will ever point to osr methods, so we can just remove it

      release_nmethod(nm);

      _flushed_count++;

    } else {

      nm->make_zombie();

      _resweep = true;

      _zombified_count++;

      SWEEP(nm);

    }

  } else {

    assert(nm->is_alive(), "should be alive");

    if (UseCodeCacheFlushing) {

      if (nm->is_speculatively_disconnected() && !nm->is_locked_by_vm() && !nm->is_osr_method() &&

          (_traversals > _last_flush_traversal_id + 2) && (nm->compile_id() < _highest_marked)) {

        // This method has not been called since the forced cleanup happened

        nm->make_not_entrant();

      }

    }

    // Clean-up all inline caches that points to zombie/non-reentrant methods

    MutexLocker cl(CompiledIC_lock);

    nm->cleanup_inline_caches();

    SWEEP(nm);

  }

}