[mc] Config to disable soft-dirty page tracking --cfg=model-check/soft-dirty:yes

[simgrid.git] / src / mc / mc_page_snapshot.cpp

diff --git a/src/mc/mc_page_snapshot.cpp b/src/mc/mc_page_snapshot.cpp
index 549101a..4a964ac 100644 (file)
--- a/src/mc/mc_page_snapshot.cpp
+++ b/src/mc/mc_page_snapshot.cpp
@@ -1,6 +1,8 @@
 #include "mc_page_store.h"
 #include "mc_mmu.h"
 
+#include <xbt/mmalloc.h>
+
 #define SOFT_DIRTY_BIT_NUMBER 55
 #define SOFT_DIRTY (((uint64_t)1) << SOFT_DIRTY_BIT_NUMBER)
 
@@ -67,14 +69,15 @@ static size_t pread_whole(int fd, void* buf, size_t count, off_t offset) {
     if (n==0)
       return res;
 
-    // Error (or EAGAIN):
+    // Error (or EINTR):
     if (n==-1) {
-      if (errno == EAGAIN)
+      if (errno == EINTR)
         continue;
       else
         return -1;
     }
 
+    // It might be a partial read:
     count -= n;
     data += n;
     offset += n;
@@ -93,11 +96,13 @@ static inline void mc_ensure_fd(int* fd, const char* path, int flags) {
   }
 }
 
-/** @brief Reset the softdirty bits
+/** @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);
@@ -106,13 +111,16 @@ void mc_softdirty_reset() {
   }
 }
 
-/** @brief Read /proc/self/pagemap informations in order to find properties on the pages
+/** @brief Read memory page informations
  *
- *  For each virtual memory page, this file provides 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.
  *
+ *  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
@@ -143,8 +151,8 @@ mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc
   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);
+  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);
   }
 
@@ -152,6 +160,9 @@ mc_mem_region_t mc_region_new_sparse(int type, void *start_addr, size_t size, mc
   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;
 }
 
@@ -164,13 +175,19 @@ void mc_region_restore_sparse(mc_mem_region_t reg, mc_mem_region_t ref_reg)
   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);
+  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);
+  }
 }
 
 }