X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/82bebb568ecbca2bcac029c94e62e7e332743a58..8454ea5fa71f9a14328f16aec13537e592912d48:/src/mc/mc_page_snapshot.cpp

diff --git a/src/mc/mc_page_snapshot.cpp b/src/mc/mc_page_snapshot.cpp
index 4a964acab3..7bb42f03d1 100644
--- a/src/mc/mc_page_snapshot.cpp
+++ b/src/mc/mc_page_snapshot.cpp
@@ -1,193 +1,94 @@
-#include "mc_page_store.h"
-#include "mc_mmu.h"
+/* MC interface: definitions that non-MC modules must see, but not the user */
 
-#include <xbt/mmalloc.h>
+/* Copyright (c) 2014-2015. The SimGrid Team.  All rights reserved.         */
 
-#define SOFT_DIRTY_BIT_NUMBER 55
-#define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
+/* 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. */
 
-extern "C" {
+#include <unistd.h> // pread, pwrite
 
-// ***** Region management:
+#include "PageStore.hpp"
+#include "mc_mmu.h"
+#include "mc_private.h"
+#include "mc_snapshot.h"
 
-size_t* mc_take_page_snapshot_region(void* data, size_t page_count, uint64_t* pagemap, size_t* reference_pages)
-{
-  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) {
-      // 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);
-    }
-  }
+#include <xbt/mmalloc.h>
 
-  return pagenos;
-}
+using simgrid::mc::remote;
 
-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]);
-  }
-}
+namespace simgrid {
+namespace mc {
 
-void mc_restore_page_snapshot_region(mc_mem_region_t region, size_t page_count, uint64_t* pagemap, mc_mem_region_t reference_region)
+/** @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
+ */
+PerPageCopy::PerPageCopy(PageStore& store, AddressSpace& as,
+    remote_ptr<void> addr, std::size_t page_count)
 {
-  for (size_t i=0; i!=page_count; ++i) {
+  store_ = &store;
+  this->pagenos_.resize(page_count);
+  std::vector<char> buffer(xbt_pagesize);
 
-    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;
-    }
+  for (size_t i = 0; i != page_count; ++i) {
 
-    // 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);
-  }
-}
+      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");
 
-// ***** 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;
-  }
+        /* 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).
+        */
 
-  return res;
-}
+        as.read_bytes(
+          buffer.data(), xbt_pagesize, page,
+          simgrid::mc::ProcessIndexDisabled);
+
+      pagenos_[i] = store_->store_page(buffer.data());
 
-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
- *
- *  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)
-{
-  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;
-
-  xbt_assert((((uintptr_t)start_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);
-
-  if(pagemap) {
-    mfree((xbt_mheap_t) mc_heap, pagemap);
-  }
-  return new_reg;
-}
-
-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());
 }
 
 }