1 /* Copyright (c) 2014. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
8 #include <string.h> // memcpy, memcp
10 #include <boost/foreach.hpp>
14 #include "mc_page_store.h"
18 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_page_snapshot, mc,
19 "Logging specific to mc_page_snapshot");
23 static void mc_read_pagemap(uint64_t* pagemap, size_t page_start, size_t page_count);
29 /** @brief Compte a hash for the given memory page
31 * The page is used before inserting the page in the page store
32 * in order to find duplicate of this pae in the page store.
34 * @param data Memory page
35 * @return hash off the page
37 static inline uint64_t mc_hash_page(const void* data)
39 const uint64_t* values = (const uint64_t*) data;
40 size_t n = xbt_pagesize / sizeof(uint64_t);
44 for (size_t i=0; i!=n; ++i) {
45 hash = ((hash << 5) + hash) + values[i];
50 // ***** snapshot_page_manager
52 s_mc_pages_store::s_mc_pages_store(size_t size) :
53 memory_(NULL), capacity_(0), top_index_(0)
55 // Using mmap in order to be able to expand the region
56 // by relocating it somewhere else in the virtual memory
58 void * memory = ::mmap(NULL, size << xbt_pagebits, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
59 if (memory==MAP_FAILED) {
60 xbt_die("Could not mmap initial snapshot pages.");
64 this->capacity_ = size;
65 this->memory_ = memory;
66 this->page_counts_.resize(size);
69 s_mc_pages_store::~s_mc_pages_store()
71 ::munmap(this->memory_, this->capacity_ << xbt_pagebits);
74 void s_mc_pages_store::resize(size_t size)
76 size_t old_bytesize = this->capacity_ << xbt_pagebits;
77 size_t new_bytesize = size << xbt_pagebits;
79 // Expand the memory region by moving it into another
80 // virtual memory address if necessary:
81 void* new_memory = mremap(this->memory_, old_bytesize, new_bytesize, MREMAP_MAYMOVE);
82 if (new_memory == MAP_FAILED) {
83 xbt_die("Could not mremap snapshot pages.");
86 this->capacity_ = size;
87 this->memory_ = new_memory;
88 this->page_counts_.resize(size, 0);
91 /** Allocate a free page
93 * @return index of the free page
95 size_t s_mc_pages_store::alloc_page()
97 if (this->free_pages_.empty()) {
100 if (this->top_index_ == this->capacity_) {
101 // All the pages are allocated, we need add more pages:
102 this->resize(2 * this->capacity_);
105 // Use a page from the top:
106 return this->top_index_++;
110 // Use a page from free_pages_ (inside of the region):
111 size_t res = this->free_pages_[this->free_pages_.size() - 1];
112 this->free_pages_.pop_back();
118 void s_mc_pages_store::remove_page(size_t pageno)
120 this->free_pages_.push_back(pageno);
121 void* page = mc_page_from_number(this->memory_, pageno);
122 uint64_t hash = mc_hash_page(page);
123 this->hash_index_[hash].erase(pageno);
126 /** Store a page in memory */
127 size_t s_mc_pages_store::store_page(void* page)
129 xbt_assert(mc_page_offset(page)==0, "Not at the beginning of a page");
130 xbt_assert(top_index_ <= this->capacity_, "top_index is not consistent");
132 // First, we check if a page with the same content is already in the page
134 // 1. compute the hash of the page;
135 // 2. find pages with the same hash using `hash_index_`;
136 // 3. find a page with the same content.
137 uint64_t hash = mc_hash_page(page);
138 page_set_type& page_set = this->hash_index_[hash];
139 BOOST_FOREACH (size_t pageno, page_set) {
140 const void* snapshot_page = this->get_page(pageno);
141 if (memcmp(page, snapshot_page, xbt_pagesize) == 0) {
143 // If a page with the same content is already in the page store it is
144 // reused and its reference count is incremented.
145 page_counts_[pageno]++;
151 // Otherwise, a new page is allocated in the page store and the content
152 // of the page is `memcpy()`-ed to this new page.
153 size_t pageno = alloc_page();
154 void* snapshot_page = (void*) this->get_page(pageno);
155 memcpy(snapshot_page, page, xbt_pagesize);
156 page_set.insert(pageno);
157 page_counts_[pageno]++;
165 const void* mc_page_store_get_page(mc_pages_store_t page_store, size_t pageno)
167 return page_store->get_page(pageno);
170 mc_pages_store_t mc_pages_store_new()
172 return new s_mc_pages_store_t(500);