neverFreeMemory.cxx
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1 /**
2  * PANDA 3D SOFTWARE
3  * Copyright (c) Carnegie Mellon University. All rights reserved.
4  *
5  * All use of this software is subject to the terms of the revised BSD
6  * license. You should have received a copy of this license along
7  * with this source code in a file named "LICENSE."
8  *
9  * @file neverFreeMemory.cxx
10  * @author drose
11  * @date 2007-06-14
12  */
13 
14 #include "neverFreeMemory.h"
15 #include "atomicAdjust.h"
16 #include "memoryHook.h"
17 
18 NeverFreeMemory * TVOLATILE NeverFreeMemory::_global_ptr;
19 
20 // If a page has fewer than this many bytes remaining, never mind about it.
21 static const size_t min_page_remaining_size = 16;
22 
23 // We always allocate at least this many bytes at a time.
24 static const size_t min_page_size = 128 * 1024; // 128K
25 
26 /**
27  *
28  */
29 NeverFreeMemory::
30 NeverFreeMemory() {
31  _total_alloc = 0;
32  _total_used = 0;
33 }
34 
35 /**
36  *
37  */
38 void *NeverFreeMemory::
39 ns_alloc(size_t size) {
40  _lock.acquire();
41 
42  //NB: we no longer do alignment here. The only class that uses this is
43  // DeletedBufferChain, and we can do the alignment potentially more
44  // efficiently there since we don't end up overallocating as much.
45  _total_used += size;
46 
47  // Look for a page that has sufficient space remaining.
48 
49  Pages::iterator pi = _pages.lower_bound(Page(NULL, size));
50  if (pi != _pages.end()) {
51  // Here's a page with enough remaining space.
52  Page page = (*pi);
53  _pages.erase(pi);
54  void *result = page.alloc(size);
55  if (page._remaining >= min_page_remaining_size) {
56  _pages.insert(page);
57  }
58  _lock.release();
59  return result;
60  }
61 
62  // We have to allocate a new page. Allocate at least min_page_size bytes,
63  // and then round that up to the next _page_size bytes.
64  size_t needed_size = max(size, min_page_size);
65  needed_size = memory_hook->round_up_to_page_size(needed_size);
66  void *start = memory_hook->mmap_alloc(needed_size, false);
67  _total_alloc += needed_size;
68 
69  Page page(start, needed_size);
70  void *result = page.alloc(size);
71  if (page._remaining >= min_page_remaining_size) {
72  _pages.insert(page);
73  }
74  _lock.release();
75  return result;
76 }
77 
78 /**
79  *
80  */
81 void NeverFreeMemory::
82 make_global_ptr() {
85  ((void * TVOLATILE &)_global_ptr, (void *)NULL, (void *)ptr);
86  if (result != NULL) {
87  // Someone else got there first.
88  delete ptr;
89  }
90 }
virtual void * mmap_alloc(size_t size, bool allow_exec)
Allocates a raw page or pages of memory directly from the OS.
Definition: memoryHook.cxx:513
size_t round_up_to_page_size(size_t size) const
Rounds the indicated size request up to the next larger multiple of page_size, to qualify it for a ca...
Definition: memoryHook.I:60
This class is used to allocate bytes of memory from a pool that is never intended to be freed...
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.
return result
Returns a new RenderEffects object that represents the same as the source state, with the new RenderE...
static ALWAYS_INLINE Pointer compare_and_exchange_ptr(Pointer &mem, Pointer old_value, Pointer new_value)
Atomic compare and exchange.
PANDA 3D SOFTWARE Copyright (c) Carnegie Mellon University.