1 #include "mc_page_store.h"
4 #define SOFT_DIRTY_BIT_NUMBER 55
5 #define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
9 // ***** Region management:
11 size_t* mc_take_page_snapshot_region(void* data, size_t page_count, uint64_t* pagemap, size_t* reference_pages)
13 size_t* pagenos = (size_t*) malloc(page_count * sizeof(size_t));
15 for (size_t i=0; i!=page_count; ++i) {
16 if (pagemap && (pagemap[i] & SOFT_DIRTY)) {
17 // The page is softclean, it is the same page as the reference page:
18 pagenos[i] = reference_pages[i];
19 mc_model_checker->pages->ref_page(reference_pages[i]);
21 // Otherwise, we need to store the page the hard hard
22 // (by reading its content):
23 void* page = (char*) data + (i << xbt_pagebits);
24 pagenos[i] = mc_model_checker->pages->store_page(page);
31 void mc_free_page_snapshot_region(size_t* pagenos, size_t page_count)
33 for (size_t i=0; i!=page_count; ++i) {
34 mc_model_checker->pages->unref_page(pagenos[i]);
38 void mc_restore_page_snapshot_region(mc_mem_region_t region, size_t page_count, uint64_t* pagemap, mc_mem_region_t reference_region)
40 for (size_t i=0; i!=page_count; ++i) {
42 bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
43 if (softclean && reference_region && reference_region->page_numbers[i] == region->page_numbers[i]) {
44 // The page is softclean and is the same as the reference one:
45 // the page is already in the target state.
49 // Otherwise, copy the page:
50 void* target_page = mc_page_from_number(region->start_addr, i);
51 const void* source_page = mc_model_checker->pages->get_page(region->page_numbers[i]);
52 memcpy(target_page, source_page, xbt_pagesize);
56 // ***** Soft dirty tracking
58 /** @brief Like pread() but without partial reads */
59 static size_t pread_whole(int fd, void* buf, size_t count, off_t offset) {
62 char* data = (char*) buf;
64 ssize_t n = pread(fd, buf, count, offset);
86 static inline void mc_ensure_fd(int* fd, const char* path, int flags) {
89 *fd = open(path, flags);
91 xbt_die("Could not open file %s", path);
95 /** @brief Reset the softdirty bits
97 * This is done after checkpointing and after checkpoint restoration
98 * (if per page checkpoiting is used) in order to know which pages were
101 void mc_softdirty_reset() {
102 mc_ensure_fd(&mc_model_checker->fd_clear_refs, "/proc/self/clear_refs", O_WRONLY|O_CLOEXEC);
103 if( ::write(mc_model_checker->fd_clear_refs, "4\n", 2) != 2) {
104 xbt_die("Could not reset softdirty bits");
108 /** @brief Read /proc/self/pagemap informations in order to find properties on the pages
110 * For each virtual memory page, this file provides informations.
111 * We are interested in the soft-dirty bit: with this we can track which
112 * pages were modified between snapshots/restorations and avoid
113 * copying data which was not modified.
115 * @param pagemap Output buffer for pagemap informations
116 * @param start_addr Address of the first page
117 * @param page_count Number of pages
119 static void mc_read_pagemap(uint64_t* pagemap, size_t page_start, size_t page_count)
121 mc_ensure_fd(&mc_model_checker->fd_pagemap, "/proc/self/pagemap", O_RDONLY|O_CLOEXEC);
122 size_t bytesize = sizeof(uint64_t) * page_count;
123 off_t offset = sizeof(uint64_t) * page_start;
124 if (pread_whole(mc_model_checker->fd_pagemap, pagemap, bytesize, offset) != bytesize) {
125 xbt_die("Could not read pagemap");
129 // ***** High level API
131 mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc_mem_region_t ref_reg)
133 mc_mem_region_t new_reg = xbt_new(s_mc_mem_region_t, 1);
135 new_reg->start_addr = start_addr;
136 new_reg->data = NULL;
137 new_reg->size = size;
138 new_reg->page_numbers = NULL;
140 xbt_assert((((uintptr_t)start_addr) & (xbt_pagesize-1)) == 0,
141 "Not at the beginning of a page");
142 size_t page_count = mc_page_count(size);
144 uint64_t* pagemap = NULL;
145 if (mc_model_checker->parent_snapshot) {
146 pagemap = (uint64_t*) alloca(sizeof(uint64_t) * page_count);
147 mc_read_pagemap(pagemap, mc_page_number(NULL, start_addr), page_count);
150 // Take incremental snapshot:
151 new_reg->page_numbers = mc_take_page_snapshot_region(start_addr, page_count, pagemap,
152 ref_reg==NULL ? NULL : ref_reg->page_numbers);
157 void mc_region_restore_sparse(mc_mem_region_t reg, mc_mem_region_t ref_reg)
159 xbt_assert((((uintptr_t)reg->start_addr) & (xbt_pagesize-1)) == 0,
160 "Not at the beginning of a page");
161 size_t page_count = mc_page_count(reg->size);
163 uint64_t* pagemap = NULL;
165 // Read soft-dirty bits if necessary in order to know which pages have changed:
166 if (mc_model_checker->parent_snapshot) {
167 pagemap = (uint64_t*) alloca(sizeof(uint64_t) * page_count);
168 mc_read_pagemap(pagemap, mc_page_number(NULL, reg->start_addr), page_count);
171 // Incremental per-page snapshot restoration:
172 mc_restore_page_snapshot_region(reg, page_count, pagemap, ref_reg);