1 // Copyright (c) 2008, Google Inc. 2 // All rights reserved. 3 // 4 // Redistribution and use in source and binary forms, with or without 5 // modification, are permitted provided that the following conditions are 6 // met: 7 // 8 // * Redistributions of source code must retain the above copyright 9 // notice, this list of conditions and the following disclaimer. 10 // * Redistributions in binary form must reproduce the above 11 // copyright notice, this list of conditions and the following disclaimer 12 // in the documentation and/or other materials provided with the 13 // distribution. 14 // * Neither the name of Google Inc. nor the names of its 15 // contributors may be used to endorse or promote products derived from 16 // this software without specific prior written permission. 17 // 18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 29 30 // --- 31 // Author: Sanjay Ghemawat <opensource (at) google.com> 32 // 33 // A Span is a contiguous run of pages. 34 35 #ifndef TCMALLOC_SPAN_H_ 36 #define TCMALLOC_SPAN_H_ 37 38 #include <config.h> 39 #include "common.h" 40 41 namespace tcmalloc { 42 43 // Information kept for a span (a contiguous run of pages). 44 struct Span { 45 PageID start; // Starting page number 46 Length length; // Number of pages in span 47 Span* next; // Used when in link list 48 Span* prev; // Used when in link list 49 void* objects; // Linked list of free objects 50 unsigned int refcount : 16; // Number of non-free objects 51 unsigned int sizeclass : 8; // Size-class for small objects (or 0) 52 unsigned int location : 2; // Is the span on a freelist, and if so, which? 53 unsigned int sample : 1; // Sampled object? 54 55 #undef SPAN_HISTORY 56 #ifdef SPAN_HISTORY 57 // For debugging, we can keep a log events per span 58 int nexthistory; 59 char history[64]; 60 int value[64]; 61 #endif 62 63 // What freelist the span is on: IN_USE if on none, or normal or returned 64 enum { IN_USE, ON_NORMAL_FREELIST, ON_RETURNED_FREELIST }; 65 }; 66 67 #ifdef SPAN_HISTORY 68 void Event(Span* span, char op, int v = 0); 69 #else 70 #define Event(s,o,v) ((void) 0) 71 #endif 72 73 // Allocator/deallocator for spans 74 Span* NewSpan(PageID p, Length len); 75 void DeleteSpan(Span* span); 76 77 // ------------------------------------------------------------------------- 78 // Doubly linked list of spans. 79 // ------------------------------------------------------------------------- 80 81 // Initialize *list to an empty list. 82 void DLL_Init(Span* list); 83 84 // Remove 'span' from the linked list in which it resides, updating the 85 // pointers of adjacent Spans and setting span's next and prev to NULL. 86 void DLL_Remove(Span* span); 87 88 // Return true iff "list" is empty. 89 inline bool DLL_IsEmpty(const Span* list) { 90 return list->next == list; 91 } 92 93 // Add span to the front of list. 94 void DLL_Prepend(Span* list, Span* span); 95 96 // Return the length of the linked list. O(n) 97 int DLL_Length(const Span* list); 98 99 } // namespace tcmalloc 100 101 #endif // TCMALLOC_SPAN_H_ 102
