jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp@e7d0505c8a30 (annotated)

src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp@e7d0505c8a30 (annotated)

src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp

Fri, 10 Oct 2014 15:51:58 +0200

author: tschatzl
date: Fri, 10 Oct 2014 15:51:58 +0200
changeset 7257: e7d0505c8a30
parent 6690: 1772223a25a2
child 6876: 710a3c8b516e
child 9327: f96fcd9e1e1b
permissions: -rw-r--r--

8059758: Footprint regressions with JDK-8038423
Summary: Changes in JDK-8038423 always initialize (zero out) virtual memory used for auxiliary data structures. This causes a footprint regression for G1 in startup benchmarks. This is because they do not touch that memory at all, so the operating system does not actually commit these pages. The fix is to, if the initialization value of the data structures matches the default value of just committed memory (=0), do not do anything.
Reviewed-by: jwilhelm, brutisso

 /*
  * Copyright (c) 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 "classfile/javaClasses.hpp"
 #include "gc_implementation/g1/g1StringDedupQueue.hpp"
 #include "memory/gcLocker.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "utilities/stack.inline.hpp"
 G1StringDedupQueue* G1StringDedupQueue::_queue = NULL;
 const size_t        G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue
 const size_t        G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue
 G1StringDedupQueue::G1StringDedupQueue() :
   _cursor(0),
   _cancel(false),
   _empty(true),
   _dropped(0) {
   _nqueues = MAX2(ParallelGCThreads, (size_t)1);
   _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC);
   for (size_t i = 0; i < _nqueues; i++) {
     new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size);
   }
 }
 G1StringDedupQueue::~G1StringDedupQueue() {
   ShouldNotReachHere();
 }
 void G1StringDedupQueue::create() {
   assert(_queue == NULL, "One string deduplication queue allowed");
   _queue = new G1StringDedupQueue();
 }
 void G1StringDedupQueue::wait() {
   MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
   while (_queue->_empty && !_queue->_cancel) {
     ml.wait(Mutex::_no_safepoint_check_flag);
   }
 }
 void G1StringDedupQueue::cancel_wait() {
   MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
   _queue->_cancel = true;
   ml.notify();
 }
 void G1StringDedupQueue::push(uint worker_id, oop java_string) {
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint");
   assert(worker_id < _queue->_nqueues, "Invalid queue");
   // Push and notify waiter
   G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id];
   if (!worker_queue.is_full()) {
     worker_queue.push(java_string);
     if (_queue->_empty) {
       MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag);
       if (_queue->_empty) {
         // Mark non-empty and notify waiter
         _queue->_empty = false;
         ml.notify();
       }
     }
   } else {
     // Queue is full, drop the string and update the statistics
     Atomic::inc_ptr(&_queue->_dropped);
   }
 }
 oop G1StringDedupQueue::pop() {
   assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint");
   No_Safepoint_Verifier nsv;
   // Try all queues before giving up
   for (size_t tries = 0; tries < _queue->_nqueues; tries++) {
     // The cursor indicates where we left of last time
     G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor];
     while (!queue->is_empty()) {
       oop obj = queue->pop();
       // The oop we pop can be NULL if it was marked
       // dead. Just ignore those and pop the next oop.
       if (obj != NULL) {
         return obj;
       }
     }
     // Try next queue
     _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues;
   }
   // Mark empty
   _queue->_empty = true;
   return NULL;
 }
 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) {
   // A worker thread first claims a queue, which ensures exclusive
   // access to that queue, then continues to process it.
   for (;;) {
     // Grab next queue to scan
     size_t queue = cl->claim_queue();
     if (queue >= _queue->_nqueues) {
       // End of queues
       break;
     }
     // Scan the queue
     unlink_or_oops_do(cl, queue);
   }
 }
 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) {
   assert(queue < _queue->_nqueues, "Invalid queue");
   StackIterator<oop, mtGC> iter(_queue->_queues[queue]);
   while (!iter.is_empty()) {
     oop* p = iter.next_addr();
     if (*p != NULL) {
       if (cl->is_alive(*p)) {
         cl->keep_alive(p);
       } else {
         // Clear dead reference
         *p = NULL;
       }
     }
   }
 }
 void G1StringDedupQueue::print_statistics(outputStream* st) {
   st->print_cr(
     "   [Queue]\n"
     "      [Dropped: "UINTX_FORMAT"]", _queue->_dropped);
 }
 void G1StringDedupQueue::verify() {
   for (size_t i = 0; i < _queue->_nqueues; i++) {
     StackIterator<oop, mtGC> iter(_queue->_queues[i]);
     while (!iter.is_empty()) {
       oop obj = iter.next();
       if (obj != NULL) {
         guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap");
         guarantee(!obj->is_forwarded(), "Object must not be forwarded");
         guarantee(java_lang_String::is_instance(obj), "Object must be a String");
       }
     }
   }
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp@e7d0505c8a30 (annotated)

src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp