#include <unistd.h>
#include <string.h> // memcpy, memcp
+#include <sys/mman.h>
+
#include <boost/foreach.hpp>
#include <xbt.h>
#include "mc_page_store.h"
+#ifdef MC_PAGE_STORE_MD4
+#include <nettle/md4.h>
+#endif
+
#include "mc_mmu.h"
XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_page_snapshot, mc,
"Logging specific to mc_page_snapshot");
-extern "C" {
-
-static void mc_read_pagemap(uint64_t* pagemap, size_t page_start, size_t page_count);
-
-}
-
// ***** Utility:
/** @brief Compte a hash for the given memory page
*
* The page is used before inserting the page in the page store
- * in order to find duplicate of this pae in the page store.
+ * in order to find duplicate of this page in the page store.
*
* @param data Memory page
* @return hash off the page
*/
-static inline uint64_t mc_hash_page(const void* data)
+static inline __attribute__ ((always_inline))
+s_mc_pages_store::hash_type mc_hash_page(const void* data)
{
+#ifdef MC_PAGE_STORE_MD4
+ boost::array<uint64_t,2> result;
+ md4_ctx context;
+ md4_init(&context);
+ md4_update(&context, xbt_pagesize, (const uint8_t*) data);
+ md4_digest(&context, MD4_DIGEST_SIZE, (uint8_t*) &(result[0]));
+ return result;
+#else
const uint64_t* values = (const uint64_t*) data;
size_t n = xbt_pagesize / sizeof(uint64_t);
hash = ((hash << 5) + hash) + values[i];
}
return hash;
+#endif
}
// ***** snapshot_page_manager
// Using mmap in order to be able to expand the region
// by relocating it somewhere else in the virtual memory
// space:
- void * memory = ::mmap(NULL, size << xbt_pagebits, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
+ void * memory = ::mmap(NULL, size << xbt_pagebits, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_POPULATE, -1, 0);
if (memory==MAP_FAILED) {
xbt_die("Could not mmap initial snapshot pages.");
}
void s_mc_pages_store::resize(size_t size)
{
+ size_t old_bytesize = this->capacity_ << xbt_pagebits;
size_t new_bytesize = size << xbt_pagebits;
// Expand the memory region by moving it into another
// virtual memory address if necessary:
- void* new_memory = mremap(this->memory_, this->capacity_ << xbt_pagesize, new_bytesize, MREMAP_MAYMOVE);
+ void* new_memory = mremap(this->memory_, old_bytesize, new_bytesize, MREMAP_MAYMOVE);
if (new_memory == MAP_FAILED) {
xbt_die("Could not mremap snapshot pages.");
}
this->capacity_ = size;
this->memory_ = new_memory;
- this->page_counts_.resize(size);
+ this->page_counts_.resize(size, 0);
}
/** Allocate a free page
if (this->free_pages_.empty()) {
// Expand the region:
- if (top_index_ == this->capacity_) {
+ if (this->top_index_ == this->capacity_) {
// All the pages are allocated, we need add more pages:
this->resize(2 * this->capacity_);
}
void s_mc_pages_store::remove_page(size_t pageno)
{
this->free_pages_.push_back(pageno);
- void* page = mc_page_from_number(this->memory_, pageno);
- uint64_t hash = mc_hash_page(page);
+ const void* page = this->get_page(pageno);
+ hash_type hash = mc_hash_page(page);
+#ifdef MC_PAGE_STORE_MD4
+ this->hash_index_.erase(hash);
+#else
this->hash_index_[hash].erase(pageno);
+#endif
}
/** Store a page in memory */
xbt_assert(mc_page_offset(page)==0, "Not at the beginning of a page");
xbt_assert(top_index_ <= this->capacity_, "top_index is not consistent");
- // Search the page in the snapshot pages:
- uint64_t hash = mc_hash_page(page);
+ // First, we check if a page with the same content is already in the page
+ // store:
+ // 1. compute the hash of the page;
+ // 2. find pages with the same hash using `hash_index_`;
+ // 3. find a page with the same content.
+ hash_type hash = mc_hash_page(page);
+#ifdef MC_PAGE_STORE_MD4
+ s_mc_pages_store::pages_map_type::const_iterator i =
+ this->hash_index_.find(hash);
+ if (i!=this->hash_index_.cend()) {
+ // If a page with the same content is already in the page store it is
+ // reused and its reference count is incremented.
+ size_t pageno = i->second;
+ page_counts_[pageno]++;
+ return pageno;
+ }
+#else
+
+ // Try to find a duplicate in set of pages with the same hash:
page_set_type& page_set = this->hash_index_[hash];
BOOST_FOREACH (size_t pageno, page_set) {
const void* snapshot_page = this->get_page(pageno);
if (memcmp(page, snapshot_page, xbt_pagesize) == 0) {
- // Page found, reuse it:
+
+ // If a page with the same content is already in the page store it is
+ // reused and its reference count is incremented.
page_counts_[pageno]++;
return pageno;
+
}
}
+#endif
- // Allocate a new page for this page:
+ // Otherwise, a new page is allocated in the page store and the content
+ // of the page is `memcpy()`-ed to this new page.
size_t pageno = alloc_page();
+ xbt_assert(this->page_counts_[pageno]==0, "Allocated page is already used");
void* snapshot_page = (void*) this->get_page(pageno);
memcpy(snapshot_page, page, xbt_pagesize);
+#ifdef MC_PAGE_STORE_MD4
+ this->hash_index_[hash] = pageno;
+#else
page_set.insert(pageno);
+#endif
page_counts_[pageno]++;
return pageno;
}
return new s_mc_pages_store_t(500);
}
+void mc_pages_store_delete(mc_pages_store_t store)
+{
+ delete store;
+}
+
+}
+
+#ifdef SIMGRID_TEST
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <sys/mman.h>
+
+#include <memory>
+
+#include "mc/mc_page_store.h"
+
+static int value = 0;
+
+static void new_content(void* data, size_t size)
+{
+ memset(data, ++value, size);
+}
+
+static void* getpage()
+{
+ return mmap(NULL, getpagesize(), PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+}
+
+extern "C" {
+
+XBT_TEST_SUITE("mc_page_store", "Page store");
+
+XBT_TEST_UNIT("base", test_mc_page_store, "Test adding/removing pages in the store")
+{
+ xbt_test_add("Init");
+ size_t pagesize = (size_t) getpagesize();
+ std::auto_ptr<s_mc_pages_store_t> store = std::auto_ptr<s_mc_pages_store_t>(new s_mc_pages_store(500));
+ void* data = getpage();
+ xbt_test_assert(store->size()==0, "Bad size");
+
+ xbt_test_add("Store the page once");
+ new_content(data, pagesize);
+ size_t pageno1 = store->store_page(data);
+ xbt_test_assert(store->get_ref(pageno1)==1, "Bad refcount");
+ const void* copy = store->get_page(pageno1);
+ xbt_test_assert(memcmp(data, copy, pagesize)==0, "Page data should be the same");
+ xbt_test_assert(store->size()==1, "Bad size");
+
+ xbt_test_add("Store the same page again");
+ size_t pageno2 = store->store_page(data);
+ xbt_test_assert(pageno1==pageno2, "Page should be the same");
+ xbt_test_assert(store->get_ref(pageno1)==2, "Bad refcount");
+ xbt_test_assert(store->size()==1, "Bad size");
+
+ xbt_test_add("Store a new page");
+ new_content(data, pagesize);
+ size_t pageno3 = store->store_page(data);
+ xbt_test_assert(pageno1 != pageno3, "New page should be different");
+ xbt_test_assert(store->size()==2, "Bad size");
+
+ xbt_test_add("Unref pages");
+ store->unref_page(pageno1);
+ xbt_assert(store->get_ref(pageno1)==1, "Bad refcount");
+ xbt_assert(store->size()==2, "Bad size");
+ store->unref_page(pageno2);
+ xbt_test_assert(store->size()==1, "Bad size");
+
+ xbt_test_add("Reallocate page");
+ new_content(data, pagesize);
+ size_t pageno4 = store->store_page(data);
+ xbt_test_assert(pageno1 == pageno4, "Page was not reused");
+ xbt_test_assert(store->get_ref(pageno4)==1, "Bad refcount");
+ xbt_test_assert(store->size()==2, "Bad size");
+}
+
}
+
+#endif /* SIMGRID_TEST */
