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
12 #include <boost/foreach.hpp>
16 #include "mc_page_store.h"
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");
31 /** @brief Compte a hash for the given memory page
33 * The page is used before inserting the page in the page store
34 * in order to find duplicate of this page in the page store.
36 * @param data Memory page
37 * @return hash off the page
39 static inline __attribute__ ((always_inline))
40 s_mc_pages_store::hash_type mc_hash_page(const void* data)
42 #ifdef MC_PAGE_STORE_MD4
43 boost::array<uint64_t,2> result;
46 md4_update(&context, xbt_pagesize, (const uint8_t*) data);
47 md4_digest(&context, MD4_DIGEST_SIZE, (uint8_t*) &(result[0]));
50 const uint64_t* values = (const uint64_t*) data;
51 size_t n = xbt_pagesize / sizeof(uint64_t);
55 for (size_t i=0; i!=n; ++i) {
56 hash = ((hash << 5) + hash) + values[i];
62 // ***** snapshot_page_manager
64 s_mc_pages_store::s_mc_pages_store(size_t size) :
65 memory_(NULL), capacity_(0), top_index_(0)
67 // Using mmap in order to be able to expand the region
68 // by relocating it somewhere else in the virtual memory
70 void * memory = ::mmap(NULL, size << xbt_pagebits, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
71 if (memory==MAP_FAILED) {
72 xbt_die("Could not mmap initial snapshot pages.");
76 this->capacity_ = size;
77 this->memory_ = memory;
78 this->page_counts_.resize(size);
81 s_mc_pages_store::~s_mc_pages_store()
83 ::munmap(this->memory_, this->capacity_ << xbt_pagebits);
86 void s_mc_pages_store::resize(size_t size)
88 size_t old_bytesize = this->capacity_ << xbt_pagebits;
89 size_t new_bytesize = size << xbt_pagebits;
91 // Expand the memory region by moving it into another
92 // virtual memory address if necessary:
93 void* new_memory = mremap(this->memory_, old_bytesize, new_bytesize, MREMAP_MAYMOVE);
94 if (new_memory == MAP_FAILED) {
95 xbt_die("Could not mremap snapshot pages.");
98 this->capacity_ = size;
99 this->memory_ = new_memory;
100 this->page_counts_.resize(size, 0);
103 /** Allocate a free page
105 * @return index of the free page
107 size_t s_mc_pages_store::alloc_page()
109 if (this->free_pages_.empty()) {
111 // Expand the region:
112 if (this->top_index_ == this->capacity_) {
113 // All the pages are allocated, we need add more pages:
114 this->resize(2 * this->capacity_);
117 // Use a page from the top:
118 return this->top_index_++;
122 // Use a page from free_pages_ (inside of the region):
123 size_t res = this->free_pages_[this->free_pages_.size() - 1];
124 this->free_pages_.pop_back();
130 void s_mc_pages_store::remove_page(size_t pageno)
132 this->free_pages_.push_back(pageno);
133 const void* page = this->get_page(pageno);
134 hash_type hash = mc_hash_page(page);
135 #ifdef MC_PAGE_STORE_MD4
136 this->hash_index_.erase(hash);
138 this->hash_index_[hash].erase(pageno);
142 /** Store a page in memory */
143 size_t s_mc_pages_store::store_page(void* page)
145 xbt_assert(top_index_ <= this->capacity_, "top_index is not consistent");
147 // First, we check if a page with the same content is already in the page
149 // 1. compute the hash of the page;
150 // 2. find pages with the same hash using `hash_index_`;
151 // 3. find a page with the same content.
152 hash_type hash = mc_hash_page(page);
153 #ifdef MC_PAGE_STORE_MD4
154 s_mc_pages_store::pages_map_type::const_iterator i =
155 this->hash_index_.find(hash);
156 if (i!=this->hash_index_.cend()) {
157 // If a page with the same content is already in the page store it is
158 // reused and its reference count is incremented.
159 size_t pageno = i->second;
160 page_counts_[pageno]++;
165 // Try to find a duplicate in set of pages with the same hash:
166 page_set_type& page_set = this->hash_index_[hash];
167 BOOST_FOREACH (size_t pageno, page_set) {
168 const void* snapshot_page = this->get_page(pageno);
169 if (memcmp(page, snapshot_page, xbt_pagesize) == 0) {
171 // If a page with the same content is already in the page store it is
172 // reused and its reference count is incremented.
173 page_counts_[pageno]++;
180 // Otherwise, a new page is allocated in the page store and the content
181 // of the page is `memcpy()`-ed to this new page.
182 size_t pageno = alloc_page();
183 xbt_assert(this->page_counts_[pageno]==0, "Allocated page is already used");
184 void* snapshot_page = (void*) this->get_page(pageno);
185 memcpy(snapshot_page, page, xbt_pagesize);
186 #ifdef MC_PAGE_STORE_MD4
187 this->hash_index_[hash] = pageno;
189 page_set.insert(pageno);
191 page_counts_[pageno]++;
199 mc_pages_store_t mc_pages_store_new()
201 return new s_mc_pages_store_t(500);
204 void mc_pages_store_delete(mc_pages_store_t store)
217 #include <sys/mman.h>
221 #include "mc/mc_page_store.h"
223 static int value = 0;
225 static void new_content(void* data, size_t size)
227 memset(data, ++value, size);
230 static void* getpage()
232 return mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
237 XBT_TEST_SUITE("mc_page_store", "Page store");
239 XBT_TEST_UNIT("base", test_mc_page_store, "Test adding/removing pages in the store")
241 xbt_test_add("Init");
242 size_t pagesize = (size_t) getpagesize();
243 std::unique_ptr<s_mc_pages_store_t> store = std::unique_ptr<s_mc_pages_store_t>(new s_mc_pages_store(500));
244 void* data = getpage();
245 xbt_test_assert(store->size()==0, "Bad size");
247 xbt_test_add("Store the page once");
248 new_content(data, pagesize);
249 size_t pageno1 = store->store_page(data);
250 xbt_test_assert(store->get_ref(pageno1)==1, "Bad refcount");
251 const void* copy = store->get_page(pageno1);
252 xbt_test_assert(memcmp(data, copy, pagesize)==0, "Page data should be the same");
253 xbt_test_assert(store->size()==1, "Bad size");
255 xbt_test_add("Store the same page again");
256 size_t pageno2 = store->store_page(data);
257 xbt_test_assert(pageno1==pageno2, "Page should be the same");
258 xbt_test_assert(store->get_ref(pageno1)==2, "Bad refcount");
259 xbt_test_assert(store->size()==1, "Bad size");
261 xbt_test_add("Store a new page");
262 new_content(data, pagesize);
263 size_t pageno3 = store->store_page(data);
264 xbt_test_assert(pageno1 != pageno3, "New page should be different");
265 xbt_test_assert(store->size()==2, "Bad size");
267 xbt_test_add("Unref pages");
268 store->unref_page(pageno1);
269 xbt_assert(store->get_ref(pageno1)==1, "Bad refcount");
270 xbt_assert(store->size()==2, "Bad size");
271 store->unref_page(pageno2);
272 xbt_test_assert(store->size()==1, "Bad size");
274 xbt_test_add("Reallocate page");
275 new_content(data, pagesize);
276 size_t pageno4 = store->store_page(data);
277 xbt_test_assert(pageno1 == pageno4, "Page was not reused");
278 xbt_test_assert(store->get_ref(pageno4)==1, "Bad refcount");
279 xbt_test_assert(store->size()==2, "Bad size");
284 #endif /* SIMGRID_TEST */