-#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"
#include <xbt/mmalloc.h>
-#define SOFT_DIRTY_BIT_NUMBER 55
-#define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
-
-extern "C" {
+using simgrid::mc::remote;
-// ***** Region management:
+namespace simgrid {
+namespace mc {
/** @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
- * @param pagemap Linux kernel pagemap values fot this region (or NULL)
- * @param reference_pages Snapshot page numbers of the previous soft_dirty_reset (or NULL)
* @return Snapshot page numbers of this new snapshot
*/
-size_t* mc_take_page_snapshot_region(void* data, size_t page_count, uint64_t* pagemap, size_t* reference_pages)
+PerPageCopy::PerPageCopy(PageStore& store, AddressSpace& as,
+ remote_ptr<void> addr, std::size_t page_count)
{
- size_t* pagenos = (size_t*) malloc(page_count * sizeof(size_t));
-
- for (size_t i=0; i!=page_count; ++i) {
- bool softclean = pagemap && !(pagemap[i] & SOFT_DIRTY);
- if (softclean && reference_pages) {
- // 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
- // (by reading its content):
- void* page = (char*) data + (i << xbt_pagebits);
- pagenos[i] = mc_model_checker->pages->store_page(page);
- }
- }
+ store_ = &store;
+ this->pagenos_.resize(page_count);
+ std::vector<char> buffer(xbt_pagesize);
- return pagenos;
-}
+ for (size_t i = 0; i != page_count; ++i) {
-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]);
- }
-}
+ remote_ptr<void> page = remote(addr.address() + (i << xbt_pagebits));
+ xbt_assert(mc_page_offset((void*)page.address())==0,
+ "Not at the beginning of a page");
-/** @brief Restore a snapshot of a region
- *
- * If possible, the restoration will be incremental
- * (the modified pages will not be touched).
- *
- * @param data The start of the region (must be at the beginning of a page)
- * @param pag_count Number of pages of the region
- * @param pagemap Linux kernel pagemap values fot this region (or NULL)
- * @param reference_pages Snapshot page numbers of the previous soft_dirty_reset (or NULL)
- */
-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) {
+ /* 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).
+ */
- 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;
- }
+ as.read_bytes(
+ buffer.data(), xbt_pagesize, page,
+ simgrid::mc::ProcessIndexDisabled);
- // 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);
- }
-}
+ pagenos_[i] = store_->store_page(buffer.data());
-// ***** 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 __attribute__ ((always_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
- *
- * 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.
+extern "C" {
+
+/** @brief Restore a snapshot of a region
*
- * See https://www.kernel.org/doc/Documentation/vm/pagemap.txt
+ * If possible, the restoration will be incremental
+ * (the modified pages will not be touched).
*
- * @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, simgrid::mc::PerPageCopy const& pages_copy)
{
- 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 != pages_copy.page_count(); ++i) {
+ // Otherwise, copy the page:
+ void* target_page = mc_page_from_number(start_addr, i);
+ const void* source_page = pages_copy.page(i);
+ process->write_bytes(source_page, xbt_pagesize, remote(target_page));
}
}
// ***** 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)
+simgrid::mc::RegionSnapshot MC_region_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);
-
- new_reg->start_addr = start_addr;
- new_reg->data = NULL;
- new_reg->size = size;
- new_reg->page_numbers = NULL;
+ mc_process_t process = &mc_model_checker->process();
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 (_sg_mc_soft_dirty && mc_model_checker->parent_snapshot) {
- pagemap = (uint64_t*) mmalloc_no_memset((xbt_mheap_t) mc_heap, 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);
+ simgrid::mc::PerPageCopy page_data(mc_model_checker->page_store(), *process,
+ permanent_addr, page_count);
- if(pagemap) {
- mfree((xbt_mheap_t) mc_heap, pagemap);
- }
- return new_reg;
+ simgrid::mc::RegionSnapshot region(
+ region_type, start_addr, permanent_addr, size);
+ region.page_data(std::move(page_data));
+ return std::move(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(((reg->permanent_address().address()) & (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 (_sg_mc_soft_dirty && mc_model_checker->parent_snapshot) {
- pagemap = (uint64_t*) mmalloc_no_memset((xbt_mheap_t) mc_heap, 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);
-
- // This is funny, the restoration can restore the state of the current heap,
- // if this happen free(pagemap) would free from the wrong heap:
- if(pagemap) {
- mfree((xbt_mheap_t) mc_heap, pagemap);
- }
+ xbt_assert(mc_page_count(reg->size()) == reg->page_data().page_count());
+ mc_restore_page_snapshot_region(process,
+ (void*) reg->permanent_address().address(), reg->page_data());
}
}
