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"
22 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_page_snapshot, mc,
23 "Logging specific to mc_page_snapshot");
28 /** @brief Compte a hash for the given memory page
30 * The page is used before inserting the page in the page store
31 * in order to find duplicate of this page in the page store.
33 * @param data Memory page
34 * @return hash off the page
36 static inline __attribute__ ((always_inline))
37 PageStore::hash_type mc_hash_page(const void* data)
39 const std::uint64_t* values = (const uint64_t*) data;
40 std::size_t n = xbt_pagesize / sizeof(uint64_t);
43 std::uint64_t hash = 5381;
44 for (std::size_t i = 0; i != n; ++i) {
45 hash = ((hash << 5) + hash) + values[i];
50 // ***** snapshot_page_manager
52 PageStore::PageStore(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 PageStore::~PageStore()
71 ::munmap(this->memory_, this->capacity_ << xbt_pagebits);
74 void PageStore::resize(std::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 std::size_t PageStore::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 PageStore::remove_page(std::size_t pageno)
120 this->free_pages_.push_back(pageno);
121 const void* page = this->get_page(pageno);
122 hash_type hash = mc_hash_page(page);
123 this->hash_index_[hash].erase(pageno);
126 /** Store a page in memory */
127 std::size_t PageStore::store_page(void* page)
129 xbt_assert(top_index_ <= this->capacity_, "top_index is not consistent");
131 // First, we check if a page with the same content is already in the page
133 // 1. compute the hash of the page;
134 // 2. find pages with the same hash using `hash_index_`;
135 // 3. find a page with the same content.
136 hash_type hash = mc_hash_page(page);
138 // Try to find a duplicate in set of pages with the same hash:
139 page_set_type& page_set = this->hash_index_[hash];
140 BOOST_FOREACH (size_t pageno, page_set) {
141 const void* snapshot_page = this->get_page(pageno);
142 if (memcmp(page, snapshot_page, xbt_pagesize) == 0) {
144 // If a page with the same content is already in the page store it is
145 // reused and its reference count is incremented.
146 page_counts_[pageno]++;
152 // Otherwise, a new page is allocated in the page store and the content
153 // of the page is `memcpy()`-ed to this new page.
154 std::size_t pageno = alloc_page();
155 xbt_assert(this->page_counts_[pageno]==0, "Allocated page is already used");
156 void* snapshot_page = (void*) this->get_page(pageno);
157 memcpy(snapshot_page, page, xbt_pagesize);
158 page_set.insert(pageno);
159 page_counts_[pageno]++;
172 #include <sys/mman.h>
176 #include "mc/PageStore.hpp"
178 static int value = 0;
180 static void new_content(void* data, std::size_t size)
182 ::memset(data, ++value, size);
185 static void* getpage()
187 return mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
192 XBT_TEST_SUITE("mc_page_store", "Page store");
194 XBT_TEST_UNIT("base", test_mc_page_store, "Test adding/removing pages in the store")
196 using simgrid::mc::PageStore;
198 xbt_test_add("Init");
199 std::size_t pagesize = (size_t) getpagesize();
200 std::unique_ptr<PageStore> store
201 = std::unique_ptr<PageStore>(new simgrid::mc::PageStore(500));
202 void* data = getpage();
203 xbt_test_assert(store->size()==0, "Bad size");
205 xbt_test_add("Store the page once");
206 new_content(data, pagesize);
207 size_t pageno1 = store->store_page(data);
208 xbt_test_assert(store->get_ref(pageno1)==1, "Bad refcount");
209 const void* copy = store->get_page(pageno1);
210 xbt_test_assert(::memcmp(data, copy, pagesize)==0, "Page data should be the same");
211 xbt_test_assert(store->size()==1, "Bad size");
213 xbt_test_add("Store the same page again");
214 size_t pageno2 = store->store_page(data);
215 xbt_test_assert(pageno1==pageno2, "Page should be the same");
216 xbt_test_assert(store->get_ref(pageno1)==2, "Bad refcount");
217 xbt_test_assert(store->size()==1, "Bad size");
219 xbt_test_add("Store a new page");
220 new_content(data, pagesize);
221 size_t pageno3 = store->store_page(data);
222 xbt_test_assert(pageno1 != pageno3, "New page should be different");
223 xbt_test_assert(store->size()==2, "Bad size");
225 xbt_test_add("Unref pages");
226 store->unref_page(pageno1);
227 xbt_assert(store->get_ref(pageno1)==1, "Bad refcount");
228 xbt_assert(store->size()==2, "Bad size");
229 store->unref_page(pageno2);
230 xbt_test_assert(store->size()==1, "Bad size");
232 xbt_test_add("Reallocate page");
233 new_content(data, pagesize);
234 size_t pageno4 = store->store_page(data);
235 xbt_test_assert(pageno1 == pageno4, "Page was not reused");
236 xbt_test_assert(store->get_ref(pageno4)==1, "Bad refcount");
237 xbt_test_assert(store->size()==2, "Bad size");
242 #endif /* SIMGRID_TEST */