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>
24 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_page_snapshot, mc,
25 "Logging specific to mc_page_snapshot");
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 page in the page store.
34 * @param data Memory page
35 * @return hash off the page
37 static inline __attribute__ ((always_inline))
38 s_mc_pages_store::hash_type mc_hash_page(const void* data)
40 #ifdef MC_PAGE_STORE_MD4
41 boost::array<uint64_t,2> result;
44 md4_update(&context, xbt_pagesize, (const uint8_t*) data);
45 md4_digest(&context, MD4_DIGEST_SIZE, (uint8_t*) &(result[0]));
48 const uint64_t* values = (const uint64_t*) data;
49 size_t n = xbt_pagesize / sizeof(uint64_t);
53 for (size_t i=0; i!=n; ++i) {
54 hash = ((hash << 5) + hash) + values[i];
60 // ***** snapshot_page_manager
62 s_mc_pages_store::s_mc_pages_store(size_t size) :
63 memory_(NULL), capacity_(0), top_index_(0)
65 // Using mmap in order to be able to expand the region
66 // by relocating it somewhere else in the virtual memory
68 void * memory = ::mmap(NULL, size << xbt_pagebits, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
69 if (memory==MAP_FAILED) {
70 xbt_die("Could not mmap initial snapshot pages.");
74 this->capacity_ = size;
75 this->memory_ = memory;
76 this->page_counts_.resize(size);
79 s_mc_pages_store::~s_mc_pages_store()
81 ::munmap(this->memory_, this->capacity_ << xbt_pagebits);
84 void s_mc_pages_store::resize(size_t size)
86 size_t old_bytesize = this->capacity_ << xbt_pagebits;
87 size_t new_bytesize = size << xbt_pagebits;
89 // Expand the memory region by moving it into another
90 // virtual memory address if necessary:
91 void* new_memory = mremap(this->memory_, old_bytesize, new_bytesize, MREMAP_MAYMOVE);
92 if (new_memory == MAP_FAILED) {
93 xbt_die("Could not mremap snapshot pages.");
96 this->capacity_ = size;
97 this->memory_ = new_memory;
98 this->page_counts_.resize(size, 0);
101 /** Allocate a free page
103 * @return index of the free page
105 size_t s_mc_pages_store::alloc_page()
107 if (this->free_pages_.empty()) {
109 // Expand the region:
110 if (this->top_index_ == this->capacity_) {
111 // All the pages are allocated, we need add more pages:
112 this->resize(2 * this->capacity_);
115 // Use a page from the top:
116 return this->top_index_++;
120 // Use a page from free_pages_ (inside of the region):
121 size_t res = this->free_pages_[this->free_pages_.size() - 1];
122 this->free_pages_.pop_back();
128 void s_mc_pages_store::remove_page(size_t pageno)
130 this->free_pages_.push_back(pageno);
131 const void* page = this->get_page(pageno);
132 hash_type hash = mc_hash_page(page);
133 #ifdef MC_PAGE_STORE_MD4
134 this->hash_index_.erase(hash);
136 this->hash_index_[hash].erase(pageno);
140 /** Store a page in memory */
141 size_t s_mc_pages_store::store_page(void* page)
143 xbt_assert(mc_page_offset(page)==0, "Not at the beginning of a page");
144 xbt_assert(top_index_ <= this->capacity_, "top_index is not consistent");
146 // First, we check if a page with the same content is already in the page
148 // 1. compute the hash of the page;
149 // 2. find pages with the same hash using `hash_index_`;
150 // 3. find a page with the same content.
151 hash_type hash = mc_hash_page(page);
152 #ifdef MC_PAGE_STORE_MD4
153 s_mc_pages_store::pages_map_type::const_iterator i =
154 this->hash_index_.find(hash);
155 if (i!=this->hash_index_.cend()) {
156 // If a page with the same content is already in the page store it is
157 // reused and its reference count is incremented.
158 size_t pageno = i->second;
159 page_counts_[pageno]++;
164 // Try to find a duplicate in set of pages with the same hash:
165 page_set_type& page_set = this->hash_index_[hash];
166 BOOST_FOREACH (size_t pageno, page_set) {
167 const void* snapshot_page = this->get_page(pageno);
168 if (memcmp(page, snapshot_page, xbt_pagesize) == 0) {
170 // If a page with the same content is already in the page store it is
171 // reused and its reference count is incremented.
172 page_counts_[pageno]++;
179 // Otherwise, a new page is allocated in the page store and the content
180 // of the page is `memcpy()`-ed to this new page.
181 size_t pageno = alloc_page();
182 xbt_assert(this->page_counts_[pageno]==0, "Allocated page is already used");
183 void* snapshot_page = (void*) this->get_page(pageno);
184 memcpy(snapshot_page, page, xbt_pagesize);
185 #ifdef MC_PAGE_STORE_MD4
186 this->hash_index_[hash] = pageno;
188 page_set.insert(pageno);
190 page_counts_[pageno]++;
198 mc_pages_store_t mc_pages_store_new()
200 return new s_mc_pages_store_t(500);
203 void mc_pages_store_delete(mc_pages_store_t store)
216 #include <sys/mman.h>
220 #include "mc/mc_page_store.h"
222 static int value = 0;
224 static void new_content(void* data, size_t size)
226 memset(data, ++value, size);
229 static void* getpage()
231 return mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
236 XBT_TEST_SUITE("mc_page_store", "Page store");
238 XBT_TEST_UNIT("base", test_mc_page_store, "Test adding/removing pages in the store")
240 xbt_test_add("Init");
241 size_t pagesize = (size_t) getpagesize();
242 std::auto_ptr<s_mc_pages_store_t> store = std::auto_ptr<s_mc_pages_store_t>(new s_mc_pages_store(500));
243 void* data = getpage();
244 xbt_test_assert(store->size()==0, "Bad size");
246 xbt_test_add("Store the page once");
247 new_content(data, pagesize);
248 size_t pageno1 = store->store_page(data);
249 xbt_test_assert(store->get_ref(pageno1)==1, "Bad refcount");
250 const void* copy = store->get_page(pageno1);
251 xbt_test_assert(memcmp(data, copy, pagesize)==0, "Page data should be the same");
252 xbt_test_assert(store->size()==1, "Bad size");
254 xbt_test_add("Store the same page again");
255 size_t pageno2 = store->store_page(data);
256 xbt_test_assert(pageno1==pageno2, "Page should be the same");
257 xbt_test_assert(store->get_ref(pageno1)==2, "Bad refcount");
258 xbt_test_assert(store->size()==1, "Bad size");
260 xbt_test_add("Store a new page");
261 new_content(data, pagesize);
262 size_t pageno3 = store->store_page(data);
263 xbt_test_assert(pageno1 != pageno3, "New page should be different");
264 xbt_test_assert(store->size()==2, "Bad size");
266 xbt_test_add("Unref pages");
267 store->unref_page(pageno1);
268 xbt_assert(store->get_ref(pageno1)==1, "Bad refcount");
269 xbt_assert(store->size()==2, "Bad size");
270 store->unref_page(pageno2);
271 xbt_test_assert(store->size()==1, "Bad size");
273 xbt_test_add("Reallocate page");
274 new_content(data, pagesize);
275 size_t pageno4 = store->store_page(data);
276 xbt_test_assert(pageno1 == pageno4, "Page was not reused");
277 xbt_test_assert(store->get_ref(pageno4)==1, "Bad refcount");
278 xbt_test_assert(store->size()==2, "Bad size");
283 #endif /* SIMGRID_TEST */