-#include "mc_page_store.h"
+/* MC interface: definitions that non-MC modules must see, but not the user */
+
+/* Copyright (c) 2014-2015. 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 <unistd.h> // pread, pwrite
+
+#include "PageStore.hpp"
#include "mc_mmu.h"
+#include "mc_private.h"
+#include "mc_snapshot.h"
-#define SOFT_DIRTY_BIT_NUMBER 55
-#define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
+#include <xbt/mmalloc.h>
extern "C" {
// ***** Region management:
-size_t* mc_take_page_snapshot_region(void* data, size_t page_count, uint64_t* pagemap, size_t* reference_pages)
+/** @brief Take a per-page snapshot of a region
+ *
+ * @param data The start of the region (must be at the beginning of a page)
+ * @param pag_count Number of pages of the region
+ * @return Snapshot page numbers of this new snapshot
+ */
+size_t* mc_take_page_snapshot_region(mc_process_t process,
+ void* data, size_t page_count)
{
size_t* pagenos = (size_t*) malloc(page_count * sizeof(size_t));
+ const bool is_self = MC_process_is_self(process);
+
+ void* temp = NULL;
+ if (!is_self)
+ temp = malloc(xbt_pagesize);
+
for (size_t i=0; i!=page_count; ++i) {
- bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
- if (softclean) {
- // The page is softclean, it is the same page as the reference page:
- pagenos[i] = reference_pages[i];
- mc_model_checker->pages->ref_page(reference_pages[i]);
- } else {
- // Otherwise, we need to store the page the hard hard
+
+ // Otherwise, we need to store the page the hard way
// (by reading its content):
void* page = (char*) data + (i << xbt_pagebits);
- pagenos[i] = mc_model_checker->pages->store_page(page);
- }
+ xbt_assert(mc_page_offset(page)==0, "Not at the beginning of a page");
+ void* page_data;
+ if (is_self) {
+ page_data = page;
+ } else {
+ /* Adding another copy (and a syscall) will probably slow things a lot.
+ TODO, optimize this somehow (at least by grouping the syscalls)
+ if needed. Either:
+ - reduce the number of syscalls;
+ - let the application snapshot itself;
+ - move the segments in shared memory (this will break `fork` however).
+ */
+ page_data = temp;
+ MC_process_read(process, MC_ADDRESS_SPACE_READ_FLAGS_NONE,
+ temp, page, xbt_pagesize, MC_PROCESS_INDEX_DISABLED);
+ }
+ pagenos[i] = mc_model_checker->page_store().store_page(page_data);
+
}
+ free(temp);
return pagenos;
}
void mc_free_page_snapshot_region(size_t* pagenos, size_t page_count)
{
for (size_t i=0; i!=page_count; ++i) {
- mc_model_checker->pages->unref_page(pagenos[i]);
+ mc_model_checker->page_store().unref_page(pagenos[i]);
}
}
-void mc_restore_page_snapshot_region(mc_mem_region_t region, size_t page_count, uint64_t* pagemap, mc_mem_region_t reference_region)
-{
- for (size_t i=0; i!=page_count; ++i) {
-
- bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
- if (softclean && reference_region && reference_region->page_numbers[i] == region->page_numbers[i]) {
- // The page is softclean and is the same as the reference one:
- // the page is already in the target state.
- continue;
- }
-
- // Otherwise, copy the page:
- void* target_page = mc_page_from_number(region->start_addr, i);
- const void* source_page = mc_model_checker->pages->get_page(region->page_numbers[i]);
- memcpy(target_page, source_page, xbt_pagesize);
- }
-}
-
-// ***** Soft dirty tracking
-
-/** @brief Like pread() but without partial reads */
-static size_t pread_whole(int fd, void* buf, size_t count, off_t offset) {
- size_t res = 0;
-
- char* data = (char*) buf;
- while(count) {
- ssize_t n = pread(fd, buf, count, offset);
- // EOF
- if (n==0)
- return res;
-
- // Error (or EINTR):
- if (n==-1) {
- if (errno == EINTR)
- continue;
- else
- return -1;
- }
-
- // It might be a partial read:
- count -= n;
- data += n;
- offset += n;
- res += n;
- }
-
- return res;
-}
-
-static inline void mc_ensure_fd(int* fd, const char* path, int flags) {
- if (*fd != -1)
- return;
- *fd = open(path, flags);
- if (*fd == -1) {
- xbt_die("Could not open file %s", path);
- }
-}
-
-/** @brief Reset the soft-dirty bits
- *
- * This is done after checkpointing and after checkpoint restoration
- * (if per page checkpoiting is used) in order to know which pages were
- * modified.
- *
- * See https://www.kernel.org/doc/Documentation/vm/soft-dirty.txt
- * */
-void mc_softdirty_reset() {
- mc_ensure_fd(&mc_model_checker->fd_clear_refs, "/proc/self/clear_refs", O_WRONLY|O_CLOEXEC);
- if( ::write(mc_model_checker->fd_clear_refs, "4\n", 2) != 2) {
- xbt_die("Could not reset softdirty bits");
- }
-}
-
-/** @brief Read memory page informations
+/** @brief Restore a snapshot of a region
*
- * For each virtual memory page of the process,
- * /proc/self/pagemap provides a 64 bit field of information.
- * We are interested in the soft-dirty bit: with this we can track which
- * pages were modified between snapshots/restorations and avoid
- * copying data which was not modified.
+ * If possible, the restoration will be incremental
+ * (the modified pages will not be touched).
*
- * See https://www.kernel.org/doc/Documentation/vm/pagemap.txt
- *
- * @param pagemap Output buffer for pagemap informations
- * @param start_addr Address of the first page
- * @param page_count Number of pages
+ * @param start_addr
+ * @param page_count Number of pages of the region
+ * @param pagenos
*/
-static void mc_read_pagemap(uint64_t* pagemap, size_t page_start, size_t page_count)
+void mc_restore_page_snapshot_region(mc_process_t process,
+ void* start_addr, size_t page_count, size_t* pagenos)
{
- mc_ensure_fd(&mc_model_checker->fd_pagemap, "/proc/self/pagemap", O_RDONLY|O_CLOEXEC);
- size_t bytesize = sizeof(uint64_t) * page_count;
- off_t offset = sizeof(uint64_t) * page_start;
- if (pread_whole(mc_model_checker->fd_pagemap, pagemap, bytesize, offset) != bytesize) {
- xbt_die("Could not read pagemap");
+ for (size_t i=0; i!=page_count; ++i) {
+ // Otherwise, copy the page:
+ void* target_page = mc_page_from_number(start_addr, i);
+ const void* source_page = mc_model_checker->page_store().get_page(pagenos[i]);
+ MC_process_write(process, source_page, target_page, xbt_pagesize);
}
}
// ***** High level API
-mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc_mem_region_t ref_reg)
+mc_mem_region_t mc_region_new_sparse(mc_region_type_t region_type,
+ void *start_addr, void* permanent_addr, size_t size)
{
- mc_mem_region_t new_reg = xbt_new(s_mc_mem_region_t, 1);
+ mc_process_t process = &mc_model_checker->process();
- new_reg->start_addr = start_addr;
- new_reg->data = NULL;
- new_reg->size = size;
- new_reg->page_numbers = NULL;
+ mc_mem_region_t region = xbt_new(s_mc_mem_region_t, 1);
+ region->region_type = region_type;
+ region->storage_type = MC_REGION_STORAGE_TYPE_CHUNKED;
+ region->start_addr = start_addr;
+ region->permanent_addr = permanent_addr;
+ region->size = size;
xbt_assert((((uintptr_t)start_addr) & (xbt_pagesize-1)) == 0,
"Not at the beginning of a page");
+ xbt_assert((((uintptr_t)permanent_addr) & (xbt_pagesize-1)) == 0,
+ "Not at the beginning of a page");
size_t page_count = mc_page_count(size);
- uint64_t* pagemap = NULL;
- if (mc_model_checker->parent_snapshot) {
- pagemap = (uint64_t*) alloca(sizeof(uint64_t) * page_count);
- mc_read_pagemap(pagemap, mc_page_number(NULL, start_addr), page_count);
- }
-
// Take incremental snapshot:
- new_reg->page_numbers = mc_take_page_snapshot_region(start_addr, page_count, pagemap,
- ref_reg==NULL ? NULL : ref_reg->page_numbers);
+ region->chunked.page_numbers = mc_take_page_snapshot_region(process,
+ permanent_addr, page_count);
- return new_reg;
+ return region;
}
-void mc_region_restore_sparse(mc_mem_region_t reg, mc_mem_region_t ref_reg)
+void mc_region_restore_sparse(mc_process_t process, mc_mem_region_t reg)
{
- xbt_assert((((uintptr_t)reg->start_addr) & (xbt_pagesize-1)) == 0,
+ xbt_assert((((uintptr_t)reg->permanent_addr) & (xbt_pagesize-1)) == 0,
"Not at the beginning of a page");
size_t page_count = mc_page_count(reg->size);
- uint64_t* pagemap = NULL;
-
- // Read soft-dirty bits if necessary in order to know which pages have changed:
- if (mc_model_checker->parent_snapshot) {
- pagemap = (uint64_t*) alloca(sizeof(uint64_t) * page_count);
- mc_read_pagemap(pagemap, mc_page_number(NULL, reg->start_addr), page_count);
- }
-
- // Incremental per-page snapshot restoration:
- mc_restore_page_snapshot_region(reg, page_count, pagemap, ref_reg);
+ mc_restore_page_snapshot_region(process,
+ reg->permanent_addr, page_count, reg->chunked.page_numbers);
}
}