1 /*
  2  * Copyright (c) 2021, Red Hat, Inc. All rights reserved.
  3  * Copyright (c) 2020, 2025, Oracle and/or its affiliates. All rights reserved.
  4  * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
  5  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  6  *
  7  * This code is free software; you can redistribute it and/or modify it
  8  * under the terms of the GNU General Public License version 2 only, as
  9  * published by the Free Software Foundation.
 10  *
 11  * This code is distributed in the hope that it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14  * version 2 for more details (a copy is included in the LICENSE file that
 15  * accompanied this code).
 16  *
 17  * You should have received a copy of the GNU General Public License version
 18  * 2 along with this work; if not, write to the Free Software Foundation,
 19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 20  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  *
 25  */
 26 
 27 
 28 #include "gc/shenandoah/shenandoahAsserts.hpp"
 29 #include "gc/shenandoah/shenandoahClosures.inline.hpp"
 30 #include "gc/shenandoah/shenandoahCodeRoots.hpp"
 31 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 32 #include "gc/shenandoah/shenandoahStackWatermark.hpp"
 33 #include "gc/shenandoah/shenandoahUtils.hpp"
 34 #include "runtime/safepointVerifiers.hpp"
 35 
 36 uint32_t ShenandoahStackWatermark::_epoch_id = 1;
 37 
 38 ShenandoahOnStackNMethodClosure::ShenandoahOnStackNMethodClosure() :
 39     _bs_nm(BarrierSet::barrier_set()->barrier_set_nmethod()) {}
 40 
 41 void ShenandoahOnStackNMethodClosure::do_nmethod(nmethod* nm) {
 42   assert(nm != nullptr, "Sanity");
 43   const bool result = _bs_nm->nmethod_entry_barrier(nm);
 44   assert(result, "NMethod on-stack must be alive");
 45 }
 46 
 47 ThreadLocalAllocStats& ShenandoahStackWatermark::stats() {
 48   return _stats;
 49 }
 50 
 51 uint32_t ShenandoahStackWatermark::epoch_id() const {
 52   return _epoch_id;
 53 }
 54 
 55 void ShenandoahStackWatermark::change_epoch_id() {
 56   shenandoah_assert_safepoint();
 57   _epoch_id++;
 58 }
 59 
 60 ShenandoahStackWatermark::ShenandoahStackWatermark(JavaThread* jt) :
 61   StackWatermark(jt, StackWatermarkKind::gc, _epoch_id),
 62   _heap(ShenandoahHeap::heap()),
 63   _stats(),
 64   _no_op_cl(),
 65   _keep_alive_cl(),
 66   _evac_update_oop_cl(),
 67   _nm_cl() {}
 68 
 69 OopClosure* ShenandoahStackWatermark::closure_from_context(void* context) {
 70   if (context != nullptr) {
 71     assert(_heap->is_concurrent_weak_root_in_progress() ||
 72            _heap->is_concurrent_mark_in_progress(),
 73            "Only these two phases");
 74     assert(Thread::current()->is_Worker_thread(), "Unexpected thread passing in context: " PTR_FORMAT, p2i(context));
 75     return reinterpret_cast<OopClosure*>(context);
 76   } else {
 77     if (_heap->is_concurrent_weak_root_in_progress() && _heap->is_evacuation_in_progress()) {
 78       return &_evac_update_oop_cl;
 79     } else if (_heap->is_concurrent_mark_in_progress()) {
 80       return &_keep_alive_cl;
 81     } else {
 82       return &_no_op_cl;
 83     }
 84   }
 85 }
 86 
 87 void ShenandoahStackWatermark::start_processing_impl(void* context) {
 88   NoSafepointVerifier nsv;
 89 
 90   ShenandoahHeap* const heap = ShenandoahHeap::heap();
 91   if (_heap->is_concurrent_weak_root_in_progress() && heap->is_evacuation_in_progress()) {
 92     // Retire the TLABs, which will force threads to reacquire their TLABs.
 93     // This is needed for two reasons. Strong one: new allocations would be with new freeset,
 94     // which would be outside the collection set, so no cset writes would happen there.
 95     // Weaker one: new allocations would happen past update watermark, and so less work would
 96     // be needed for reference updates (would update the large filler instead).
 97     retire_tlab();
 98   } else if (heap->is_concurrent_mark_in_progress()) {
 99     // We need to reset all TLABs because they might be below the TAMS, and we need to mark
100     // the objects in them. Do not let mutators allocate any new objects in their current TLABs.
101     // It is also a good place to resize the TLAB sizes for future allocations.
102     retire_tlab();
103   } else {
104     // Can be here for updating barriers. No TLAB retirement is needed.
105   }
106 
107   // Process the non-frame part of the thread
108   _jt->oops_do_no_frames(closure_from_context(context), &_nm_cl);
109 
110   // Publishes the processing start to concurrent threads
111   StackWatermark::start_processing_impl(context);
112 }
113 
114 void ShenandoahStackWatermark::retire_tlab() {
115   // Retire TLAB
116   if (UseTLAB) {
117     _stats.reset();
118     _jt->retire_tlab(&_stats);
119     if (ResizeTLAB) {
120       _jt->tlab().resize();
121     }
122   }
123 }
124 
125 void ShenandoahStackWatermark::process(const frame& fr, RegisterMap& register_map, void* context) {
126   OopClosure* oops = closure_from_context(context);
127   assert(oops != nullptr, "Should not get to here");
128   ShenandoahHeap* const heap = ShenandoahHeap::heap();
129   fr.oops_do(oops, &_nm_cl, &register_map, DerivedPointerIterationMode::_directly);
130 }