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 bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
18 // The page is softclean, it is the same page as the reference page:
19 pagenos[i] = reference_pages[i];
20 mc_model_checker->pages->ref_page(reference_pages[i]);
22 // Otherwise, we need to store the page the hard hard
23 // (by reading its content):
24 void* page = (char*) data + (i << xbt_pagebits);
25 pagenos[i] = mc_model_checker->pages->store_page(page);
32 void mc_free_page_snapshot_region(size_t* pagenos, size_t page_count)
34 for (size_t i=0; i!=page_count; ++i) {
35 mc_model_checker->pages->unref_page(pagenos[i]);
39 void mc_restore_page_snapshot_region(mc_mem_region_t region, size_t page_count, uint64_t* pagemap, mc_mem_region_t reference_region)
41 for (size_t i=0; i!=page_count; ++i) {
43 bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
44 if (softclean && reference_region && reference_region->page_numbers[i] == region->page_numbers[i]) {
45 // The page is softclean and is the same as the reference one:
46 // the page is already in the target state.
50 // Otherwise, copy the page:
51 void* target_page = mc_page_from_number(region->start_addr, i);
52 const void* source_page = mc_model_checker->pages->get_page(region->page_numbers[i]);
53 memcpy(target_page, source_page, xbt_pagesize);
57 // ***** Soft dirty tracking
59 /** @brief Like pread() but without partial reads */
60 static size_t pread_whole(int fd, void* buf, size_t count, off_t offset) {
63 char* data = (char*) buf;
65 ssize_t n = pread(fd, buf, count, offset);
78 // It might be a partial read:
88 static inline void mc_ensure_fd(int* fd, const char* path, int flags) {
91 *fd = open(path, flags);
93 xbt_die("Could not open file %s", path);
97 /** @brief Reset the soft-dirty bits
99 * This is done after checkpointing and after checkpoint restoration
100 * (if per page checkpoiting is used) in order to know which pages were
103 * See https://www.kernel.org/doc/Documentation/vm/soft-dirty.txt
105 void mc_softdirty_reset() {
106 mc_ensure_fd(&mc_model_checker->fd_clear_refs, "/proc/self/clear_refs", O_WRONLY|O_CLOEXEC);
107 if( ::write(mc_model_checker->fd_clear_refs, "4\n", 2) != 2) {
108 xbt_die("Could not reset softdirty bits");
112 /** @brief Read memory page informations
114 * For each virtual memory page of the process,
115 * /proc/self/pagemap provides a 64 bit field of information.
116 * We are interested in the soft-dirty bit: with this we can track which
117 * pages were modified between snapshots/restorations and avoid
118 * copying data which was not modified.
120 * See https://www.kernel.org/doc/Documentation/vm/pagemap.txt
122 * @param pagemap Output buffer for pagemap informations
123 * @param start_addr Address of the first page
124 * @param page_count Number of pages
126 static void mc_read_pagemap(uint64_t* pagemap, size_t page_start, size_t page_count)
128 mc_ensure_fd(&mc_model_checker->fd_pagemap, "/proc/self/pagemap", O_RDONLY|O_CLOEXEC);
129 size_t bytesize = sizeof(uint64_t) * page_count;
130 off_t offset = sizeof(uint64_t) * page_start;
131 if (pread_whole(mc_model_checker->fd_pagemap, pagemap, bytesize, offset) != bytesize) {
132 xbt_die("Could not read pagemap");
136 // ***** High level API
138 mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc_mem_region_t ref_reg)
140 mc_mem_region_t new_reg = xbt_new(s_mc_mem_region_t, 1);
142 new_reg->start_addr = start_addr;
143 new_reg->data = NULL;
144 new_reg->size = size;
145 new_reg->page_numbers = NULL;
147 xbt_assert((((uintptr_t)start_addr) & (xbt_pagesize-1)) == 0,
148 "Not at the beginning of a page");
149 size_t page_count = mc_page_count(size);
151 uint64_t* pagemap = NULL;
152 if (mc_model_checker->parent_snapshot) {
153 pagemap = (uint64_t*) alloca(sizeof(uint64_t) * page_count);
154 mc_read_pagemap(pagemap, mc_page_number(NULL, start_addr), page_count);
157 // Take incremental snapshot:
158 new_reg->page_numbers = mc_take_page_snapshot_region(start_addr, page_count, pagemap,
159 ref_reg==NULL ? NULL : ref_reg->page_numbers);
164 void mc_region_restore_sparse(mc_mem_region_t reg, mc_mem_region_t ref_reg)
166 xbt_assert((((uintptr_t)reg->start_addr) & (xbt_pagesize-1)) == 0,
167 "Not at the beginning of a page");
168 size_t page_count = mc_page_count(reg->size);
170 uint64_t* pagemap = NULL;
172 // Read soft-dirty bits if necessary in order to know which pages have changed:
173 if (mc_model_checker->parent_snapshot) {
174 pagemap = (uint64_t*) alloca(sizeof(uint64_t) * page_count);
175 mc_read_pagemap(pagemap, mc_page_number(NULL, reg->start_addr), page_count);
178 // Incremental per-page snapshot restoration:
179 mc_restore_page_snapshot_region(reg, page_count, pagemap, ref_reg);