1 | // -*- C++ -*- |
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2 | |
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3 | /** |
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4 | * @file manageonesuperblock.h |
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5 | * @author Emery Berger <http://www.cs.umass.edu/~emery> |
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6 | */ |
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7 | |
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8 | |
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9 | #ifndef _MANAGEONESUPERBLOCK_H_ |
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10 | #define _MANAGEONESUPERBLOCK_H_ |
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11 | |
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12 | /** |
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13 | * @class ManageOneSuperblock |
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14 | * @brief A layer that caches exactly one superblock, thus avoiding costly lookups. |
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15 | * @author Emery Berger <http://www.cs.umass.edu/~emery> |
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16 | */ |
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17 | |
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18 | namespace Hoard { |
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19 | |
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20 | template <class SuperHeap> |
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21 | class ManageOneSuperblock : public SuperHeap { |
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22 | public: |
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23 | |
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24 | typedef typename SuperHeap::SuperblockType SuperblockType; |
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25 | |
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26 | /// Get memory from the current superblock. |
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27 | inline void * malloc (size_t sz) { |
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28 | if (_current) { |
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29 | void * ptr = _current->malloc (sz); |
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30 | if (ptr) { |
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31 | assert (_current->getSize(ptr) >= sz); |
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32 | return ptr; |
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33 | } |
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34 | } |
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35 | return slowMallocPath (sz); |
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36 | } |
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37 | |
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38 | /// Try to free the pointer to this superblock first. |
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39 | inline void free (void * ptr) { |
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40 | SuperblockType * s = SuperHeap::getSuperblock (ptr); |
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41 | if (s == _current) { |
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42 | _current->free (ptr); |
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43 | } else { |
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44 | SuperHeap::free (ptr); |
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45 | } |
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46 | } |
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47 | |
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48 | /// Get the current superblock and remove it. |
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49 | SuperblockType * get (void) { |
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50 | if (_current) { |
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51 | SuperblockType * s = _current; |
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52 | _current = NULL; |
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53 | return s; |
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54 | } else { |
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55 | // There's none cached, so just get one from the superheap. |
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56 | return SuperHeap::get(); |
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57 | } |
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58 | } |
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59 | |
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60 | /// Put the superblock into the cache. |
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61 | inline void put (SuperblockType * s) { |
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62 | if (!s || (s == _current) || (!s->isValidSuperblock())) { |
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63 | // Ignore if we already are holding this superblock, of if we |
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64 | // got a NULL pointer, or if it's invalid. |
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65 | return; |
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66 | } |
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67 | if (_current) { |
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68 | // We have one already -- push it out. |
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69 | SuperHeap::put (_current); |
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70 | } |
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71 | _current = s; |
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72 | } |
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73 | |
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74 | private: |
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75 | |
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76 | /// Obtain a superblock and return an object from it. |
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77 | void * slowMallocPath (size_t sz) { |
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78 | void * ptr = NULL; |
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79 | while (!ptr) { |
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80 | if (_current) { |
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81 | ptr = _current->malloc (sz); |
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82 | if (ptr) { |
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83 | return ptr; |
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84 | } else { |
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85 | SuperHeap::put (_current); |
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86 | } |
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87 | } |
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88 | _current = SuperHeap::get(); |
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89 | if (!_current) { |
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90 | return NULL; |
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91 | } |
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92 | ptr = _current->malloc (sz); |
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93 | } |
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94 | return ptr; |
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95 | } |
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96 | |
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97 | /// The current superblock. |
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98 | SuperblockType * _current; |
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99 | |
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100 | }; |
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101 | |
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102 | } |
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103 | |
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104 | #endif |
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