1 /*
   2  * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 #include "precompiled.hpp"
  25 #include "gc/z/zLock.inline.hpp"
  26 #include "gc/z/zMarkStack.inline.hpp"
  27 #include "gc/z/zMarkStackAllocator.hpp"
  28 #include "logging/log.hpp"
  29 #include "runtime/atomic.hpp"
  30 #include "runtime/os.hpp"
  31 #include "utilities/debug.hpp"
  32 
  33 uintptr_t ZMarkStackSpaceStart;
  34 
  35 ZMarkStackSpace::ZMarkStackSpace() :
  36     _expand_lock(),
  37     _start(0),
  38     _top(0),
  39     _end(0) {
  40   assert(ZMarkStackSpaceLimit >= ZMarkStackSpaceExpandSize, "ZMarkStackSpaceLimit too small");
  41 
  42   // Reserve address space
  43   const size_t size = ZMarkStackSpaceLimit;
  44   const size_t alignment = (size_t)os::vm_allocation_granularity();
  45   const uintptr_t addr = (uintptr_t)os::reserve_memory(size, NULL, alignment, mtGC);
  46   if (addr == 0) {
  47     log_error(gc, marking)("Failed to reserve address space for mark stacks");
  48     return;
  49   }
  50 
  51   // Successfully initialized
  52   _start = _top = _end = addr;
  53 
  54   // Register mark stack space start
  55   ZMarkStackSpaceStart = _start;
  56 }
  57 
  58 bool ZMarkStackSpace::is_initialized() const {
  59   return _start != 0;
  60 }
  61 
  62 uintptr_t ZMarkStackSpace::alloc_space(size_t size) {
  63   uintptr_t top = Atomic::load(&_top);
  64 
  65   for (;;) {
  66     const uintptr_t end = Atomic::load(&_end);
  67     const uintptr_t new_top = top + size;
  68     if (new_top > end) {
  69       // Not enough space left
  70       return 0;
  71     }
  72 
  73     const uintptr_t prev_top = Atomic::cmpxchg(&_top, top, new_top);
  74     if (prev_top == top) {
  75       // Success
  76       return top;
  77     }
  78 
  79     // Retry
  80     top = prev_top;
  81   }
  82 }
  83 
  84 uintptr_t ZMarkStackSpace::expand_and_alloc_space(size_t size) {
  85   ZLocker<ZLock> locker(&_expand_lock);
  86 
  87   // Retry allocation before expanding
  88   uintptr_t addr = alloc_space(size);
  89   if (addr != 0) {
  90     return addr;
  91   }
  92 
  93   // Check expansion limit
  94   const size_t expand_size = ZMarkStackSpaceExpandSize;
  95   const size_t old_size = _end - _start;
  96   const size_t new_size = old_size + expand_size;
  97   if (new_size > ZMarkStackSpaceLimit) {
  98     // Expansion limit reached. This is a fatal error since we
  99     // currently can't recover from running out of mark stack space.
 100     fatal("Mark stack space exhausted. Use -XX:ZMarkStackSpaceLimit=<size> to increase the "
 101           "maximum number of bytes allocated for mark stacks. Current limit is " SIZE_FORMAT "M.",
 102           ZMarkStackSpaceLimit / M);
 103   }
 104 
 105   log_debug(gc, marking)("Expanding mark stack space: " SIZE_FORMAT "M->" SIZE_FORMAT "M",
 106                          old_size / M, new_size / M);
 107 
 108   // Expand
 109   os::commit_memory_or_exit((char*)_end, expand_size, false /* executable */, "Mark stack space");
 110 
 111   // Increment top before end to make sure another
 112   // thread can't steal out newly expanded space.
 113   addr = Atomic::add(&_top, size) - size;
 114   Atomic::add(&_end, expand_size);
 115 
 116   return addr;
 117 }
 118 
 119 uintptr_t ZMarkStackSpace::alloc(size_t size) {
 120   const uintptr_t addr = alloc_space(size);
 121   if (addr != 0) {
 122     return addr;
 123   }
 124 
 125   return expand_and_alloc_space(size);
 126 }
 127 
 128 ZMarkStackAllocator::ZMarkStackAllocator() :
 129     _freelist(),
 130     _space() {
 131   guarantee(sizeof(ZMarkStack) == ZMarkStackSize, "Size mismatch");
 132   guarantee(sizeof(ZMarkStackMagazine) <= ZMarkStackSize, "Size mismatch");
 133 
 134   // Prime free list to avoid an immediate space
 135   // expansion when marking starts.
 136   if (_space.is_initialized()) {
 137     prime_freelist();
 138   }
 139 }
 140 
 141 bool ZMarkStackAllocator::is_initialized() const {
 142   return _space.is_initialized();
 143 }
 144 
 145 void ZMarkStackAllocator::prime_freelist() {
 146   for (size_t size = 0; size < ZMarkStackSpaceExpandSize; size += ZMarkStackMagazineSize) {
 147     const uintptr_t addr = _space.alloc(ZMarkStackMagazineSize);
 148     ZMarkStackMagazine* const magazine = create_magazine_from_space(addr, ZMarkStackMagazineSize);
 149     free_magazine(magazine);
 150   }
 151 }
 152 
 153 ZMarkStackMagazine* ZMarkStackAllocator::create_magazine_from_space(uintptr_t addr, size_t size) {
 154   assert(is_aligned(size, ZMarkStackSize), "Invalid size");
 155 
 156   // Use first stack as magazine
 157   ZMarkStackMagazine* const magazine = new ((void*)addr) ZMarkStackMagazine();
 158   for (size_t i = ZMarkStackSize; i < size; i += ZMarkStackSize) {
 159     ZMarkStack* const stack = new ((void*)(addr + i)) ZMarkStack();
 160     const bool success = magazine->push(stack);
 161     assert(success, "Magazine should never get full");
 162   }
 163 
 164   return magazine;
 165 }
 166 
 167 ZMarkStackMagazine* ZMarkStackAllocator::alloc_magazine() {
 168   // Try allocating from the free list first
 169   ZMarkStackMagazine* const magazine = _freelist.pop();
 170   if (magazine != NULL) {
 171     return magazine;
 172   }
 173 
 174   // Allocate new magazine
 175   const uintptr_t addr = _space.alloc(ZMarkStackMagazineSize);
 176   if (addr == 0) {
 177     return NULL;
 178   }
 179 
 180   return create_magazine_from_space(addr, ZMarkStackMagazineSize);
 181 }
 182 
 183 void ZMarkStackAllocator::free_magazine(ZMarkStackMagazine* magazine) {
 184   _freelist.push(magazine);
 185 }