+++ /dev/null
-/* Copyright (c) 2015-2018. The SimGrid Team. All rights reserved. */
-
-/* This program is free software; you can redistribute it and/or modify it
- * under the terms of the license (GNU LGPL) which comes with this package. */
-
-#include <cstring> // memcpy, memcmp
-#include <unistd.h>
-
-#include <sys/mman.h>
-#ifdef __FreeBSD__
-#define MAP_POPULATE MAP_PREFAULT_READ
-#endif
-
-#include "xbt/base.h"
-#include "xbt/log.h"
-#include "xbt/sysdep.h"
-
-#include "src/internal_config.h"
-
-#include "src/mc/sosp/PageStore.hpp"
-
-#include "src/mc/mc_mmu.hpp"
-
-XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_page_snapshot, mc, "Logging specific to mc_page_snapshot");
-
-namespace simgrid {
-namespace mc {
-
-/** @brief Compute 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 page in the page store.
- *
- * @param data Memory page
- * @return hash off the page
- */
-static XBT_ALWAYS_INLINE PageStore::hash_type mc_hash_page(const void* data)
-{
- const std::uint64_t* values = (const uint64_t*)data;
- std::size_t n = xbt_pagesize / sizeof(uint64_t);
-
- // This djb2:
- std::uint64_t hash = 5381;
- for (std::size_t i = 0; i != n; ++i)
- hash = ((hash << 5) + hash) + values[i];
- return hash;
-}
-
-// ***** snapshot_page_manager
-
-PageStore::PageStore(std::size_t size) : memory_(nullptr), capacity_(size), top_index_(0)
-{
- // Using mmap in order to be able to expand the region by relocating it somewhere else in the virtual memory space:
- void* memory =
- ::mmap(nullptr, 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.");
-
- this->top_index_ = 0;
- this->memory_ = memory;
- this->page_counts_.resize(size);
-}
-
-PageStore::~PageStore()
-{
- ::munmap(this->memory_, this->capacity_ << xbt_pagebits);
-}
-
-void PageStore::resize(std::size_t size)
-{
- size_t old_bytesize = this->capacity_ << xbt_pagebits;
- size_t new_bytesize = size << xbt_pagebits;
- void* new_memory;
-
- // Expand the memory region by moving it into another
- // virtual memory address if necessary:
-#if HAVE_MREMAP
- new_memory = mremap(this->memory_, old_bytesize, new_bytesize, MREMAP_MAYMOVE);
- if (new_memory == MAP_FAILED)
- xbt_die("Could not mremap snapshot pages.");
-#else
- if (new_bytesize > old_bytesize) {
- // Grow: first try to add new space after current map
- new_memory = mmap((char*)this->memory_ + old_bytesize, new_bytesize - old_bytesize, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE, -1, 0);
- if (new_memory == MAP_FAILED)
- xbt_die("Could not mremap snapshot pages.");
- // Check if expanding worked
- if (new_memory != (char*)this->memory_ + old_bytesize) {
- // New memory segment could not be put at the end of this->memory_,
- // so cancel this one and try to rellocate everything and copy data
- munmap(new_memory, new_bytesize - old_bytesize);
- new_memory =
- mmap(nullptr, new_bytesize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE, -1, 0);
- if (new_memory == MAP_FAILED)
- xbt_die("Could not mremap snapshot pages.");
- memcpy(new_memory, this->memory_, old_bytesize);
- munmap(this->memory_, old_bytesize);
- }
- } else {
- // We don't have functions to shrink a mapping, so leave memory as
- // it is for now
- new_memory = this->memory_;
- }
-#endif
-
- this->capacity_ = size;
- this->memory_ = new_memory;
- this->page_counts_.resize(size, 0);
-}
-
-/** Allocate a free page
- *
- * @return index of the free page
- */
-std::size_t PageStore::alloc_page()
-{
- if (this->free_pages_.empty()) {
-
- // Expand the region:
- if (this->top_index_ == this->capacity_)
- // All the pages are allocated, we need add more pages:
- this->resize(2 * this->capacity_);
-
- // Use a page from the top:
- return this->top_index_++;
-
- } else {
-
- // Use a page from free_pages_ (inside of the region):
- size_t res = this->free_pages_[this->free_pages_.size() - 1];
- this->free_pages_.pop_back();
- return res;
- }
-}
-
-void PageStore::remove_page(std::size_t pageno)
-{
- this->free_pages_.push_back(pageno);
- const void* page = this->get_page(pageno);
- hash_type hash = mc_hash_page(page);
- this->hash_index_[hash].erase(pageno);
-}
-
-/** Store a page in memory */
-std::size_t PageStore::store_page(void* page)
-{
- xbt_assert(top_index_ <= this->capacity_, "top_index is not consistent");
-
- // 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);
-
- // Try to find a duplicate in set of pages with the same hash:
- page_set_type& page_set = this->hash_index_[hash];
- for (size_t const& pageno : page_set) {
- const void* snapshot_page = this->get_page(pageno);
- if (memcmp(page, snapshot_page, xbt_pagesize) == 0) {
-
- // If a page with the same content is already in the page store it's reused and its refcount is incremented.
- page_counts_[pageno]++;
- return pageno;
- }
- }
-
- // Otherwise, a new page is allocated in the page store and the content of the page is `memcpy()`-ed to this new page.
- std::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);
- page_set.insert(pageno);
- page_counts_[pageno]++;
- return pageno;
-}
-
-} // namespace mc
-} // namespace simgrid
