1 /* Copyright (c) 2015. 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
12 #include <boost/foreach.hpp>
16 #include "PageStore.hpp"
18 #ifdef MC_PAGE_STORE_MD4
19 #include <nettle/md4.h>
26 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_page_snapshot, mc,
27 "Logging specific to mc_page_snapshot");
32 /** @brief Compte a hash for the given memory page
34 * The page is used before inserting the page in the page store
35 * in order to find duplicate of this page in the page store.
37 * @param data Memory page
38 * @return hash off the page
40 static inline __attribute__ ((always_inline))
41 PageStore::hash_type mc_hash_page(const void* data)
43 #ifdef MC_PAGE_STORE_MD4
44 boost::array<uint64_t,2> result;
47 md4_update(&context, xbt_pagesize, (const uint8_t*) data);
48 md4_digest(&context, MD4_DIGEST_SIZE, (uint8_t*) &(result[0]));
51 const uint64_t* values = (const uint64_t*) data;
52 size_t n = xbt_pagesize / sizeof(uint64_t);
56 for (size_t i=0; i!=n; ++i) {
57 hash = ((hash << 5) + hash) + values[i];
63 // ***** snapshot_page_manager
65 PageStore::PageStore(size_t size) :
66 memory_(NULL), capacity_(0), top_index_(0)
68 // Using mmap in order to be able to expand the region
69 // by relocating it somewhere else in the virtual memory
71 void * memory = ::mmap(NULL, size << xbt_pagebits, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
72 if (memory==MAP_FAILED) {
73 xbt_die("Could not mmap initial snapshot pages.");
77 this->capacity_ = size;
78 this->memory_ = memory;
79 this->page_counts_.resize(size);
82 PageStore::~PageStore()
84 ::munmap(this->memory_, this->capacity_ << xbt_pagebits);
87 void PageStore::resize(size_t size)
89 size_t old_bytesize = this->capacity_ << xbt_pagebits;
90 size_t new_bytesize = size << xbt_pagebits;
92 // Expand the memory region by moving it into another
93 // virtual memory address if necessary:
94 void* new_memory = mremap(this->memory_, old_bytesize, new_bytesize, MREMAP_MAYMOVE);
95 if (new_memory == MAP_FAILED) {
96 xbt_die("Could not mremap snapshot pages.");
99 this->capacity_ = size;
100 this->memory_ = new_memory;
101 this->page_counts_.resize(size, 0);
104 /** Allocate a free page
106 * @return index of the free page
108 size_t PageStore::alloc_page()
110 if (this->free_pages_.empty()) {
112 // Expand the region:
113 if (this->top_index_ == this->capacity_) {
114 // All the pages are allocated, we need add more pages:
115 this->resize(2 * this->capacity_);
118 // Use a page from the top:
119 return this->top_index_++;
123 // Use a page from free_pages_ (inside of the region):
124 size_t res = this->free_pages_[this->free_pages_.size() - 1];
125 this->free_pages_.pop_back();
131 void PageStore::remove_page(size_t pageno)
133 this->free_pages_.push_back(pageno);
134 const void* page = this->get_page(pageno);
135 hash_type hash = mc_hash_page(page);
136 #ifdef MC_PAGE_STORE_MD4
137 this->hash_index_.erase(hash);
139 this->hash_index_[hash].erase(pageno);
143 /** Store a page in memory */
144 size_t PageStore::store_page(void* page)
146 xbt_assert(top_index_ <= this->capacity_, "top_index is not consistent");
148 // First, we check if a page with the same content is already in the page
150 // 1. compute the hash of the page;
151 // 2. find pages with the same hash using `hash_index_`;
152 // 3. find a page with the same content.
153 hash_type hash = mc_hash_page(page);
154 #ifdef MC_PAGE_STORE_MD4
155 s_mc_pages_store::pages_map_type::const_iterator i =
156 this->hash_index_.find(hash);
157 if (i!=this->hash_index_.cend()) {
158 // If a page with the same content is already in the page store it is
159 // reused and its reference count is incremented.
160 size_t pageno = i->second;
161 page_counts_[pageno]++;
166 // Try to find a duplicate in set of pages with the same hash:
167 page_set_type& page_set = this->hash_index_[hash];
168 BOOST_FOREACH (size_t pageno, page_set) {
169 const void* snapshot_page = this->get_page(pageno);
170 if (memcmp(page, snapshot_page, xbt_pagesize) == 0) {
172 // If a page with the same content is already in the page store it is
173 // reused and its reference count is incremented.
174 page_counts_[pageno]++;
181 // Otherwise, a new page is allocated in the page store and the content
182 // of the page is `memcpy()`-ed to this new page.
183 size_t pageno = alloc_page();
184 xbt_assert(this->page_counts_[pageno]==0, "Allocated page is already used");
185 void* snapshot_page = (void*) this->get_page(pageno);
186 memcpy(snapshot_page, page, xbt_pagesize);
187 #ifdef MC_PAGE_STORE_MD4
188 this->hash_index_[hash] = pageno;
190 page_set.insert(pageno);
192 page_counts_[pageno]++;
205 #include <sys/mman.h>
209 #include "mc/PageStore.hpp"
211 static int value = 0;
213 static void new_content(void* data, size_t size)
215 memset(data, ++value, size);
218 static void* getpage()
220 return mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
225 XBT_TEST_SUITE("mc_page_store", "Page store");
227 XBT_TEST_UNIT("base", test_mc_page_store, "Test adding/removing pages in the store")
229 xbt_test_add("Init");
230 size_t pagesize = (size_t) getpagesize();
231 std::unique_ptr<simgrid::mc::PageStore> store
232 = std::unique_ptr<simgrid::mc::PageStore>(new simgrid::mc::PageStore(500));
233 void* data = getpage();
234 xbt_test_assert(store->size()==0, "Bad size");
236 xbt_test_add("Store the page once");
237 new_content(data, pagesize);
238 size_t pageno1 = store->store_page(data);
239 xbt_test_assert(store->get_ref(pageno1)==1, "Bad refcount");
240 const void* copy = store->get_page(pageno1);
241 xbt_test_assert(memcmp(data, copy, pagesize)==0, "Page data should be the same");
242 xbt_test_assert(store->size()==1, "Bad size");
244 xbt_test_add("Store the same page again");
245 size_t pageno2 = store->store_page(data);
246 xbt_test_assert(pageno1==pageno2, "Page should be the same");
247 xbt_test_assert(store->get_ref(pageno1)==2, "Bad refcount");
248 xbt_test_assert(store->size()==1, "Bad size");
250 xbt_test_add("Store a new page");
251 new_content(data, pagesize);
252 size_t pageno3 = store->store_page(data);
253 xbt_test_assert(pageno1 != pageno3, "New page should be different");
254 xbt_test_assert(store->size()==2, "Bad size");
256 xbt_test_add("Unref pages");
257 store->unref_page(pageno1);
258 xbt_assert(store->get_ref(pageno1)==1, "Bad refcount");
259 xbt_assert(store->size()==2, "Bad size");
260 store->unref_page(pageno2);
261 xbt_test_assert(store->size()==1, "Bad size");
263 xbt_test_add("Reallocate page");
264 new_content(data, pagesize);
265 size_t pageno4 = store->store_page(data);
266 xbt_test_assert(pageno1 == pageno4, "Page was not reused");
267 xbt_test_assert(store->get_ref(pageno4)==1, "Bad refcount");
268 xbt_test_assert(store->size()==2, "Bad size");
273 #endif /* SIMGRID_TEST */