Intel® Advisor User Guide

User Guide

Contents

Memory Watch

Occurs when a task accesses a memory location marked by an
ANNOTATE_OBSERVE_USES
 annotation. In this case, this
problem
 provides informational feedback only and no action is required. This is useful for finding uses of specified memory locations while a task is executing.
One of the following has occurred:
Problem type: Memory watch
Problem type: Memory watch
Problem type: Memory watch
ID
Code Location
Description
1
Parallel site
If present, represents the location and associated call stack of the parallel site containing the Memory Watch problem.
2
Watch start
Represents the location and its associated call stack where an
ANNOTATE_OBSERVE_USES()
 annotation marks a memory location.
3
Read
Represents the location and associated call stack where a task read the watched memory location.
4
Write
Represents the location and associated call stack where a task wrote the watched memory location.
5
Update
Represents the location and associated call stack where a task read and wrote the watched memory location.
Example
void watch_memory()
{
   ANNOTATE_OBSERVE_USES(&watch, sizeof(watch));  // Watch start
   ANNOTATE_SITE_BEGIN(watch_site);               // Parallel site
   {
       ANNOTATE_TASK_BEGIN(watch_task1);
       {
           ANNOTATE_LOCK_ACQUIRE(&watch);
           watch++; /* watch memory */            // Read and/or Write
           ANNOTATE_LOCK_RELEASE(&watch);
       }
       ANNOTATE_TASK_END();
       ANNOTATE_TASK_BEGIN(watch_task2);
       {
           ANNOTATE_LOCK_ACQUIRE(&watch);
           watch++; /* watch memory */            // Read and/or Write
           ANNOTATE_LOCK_RELEASE(&watch);
       }
       ANNOTATE_TASK_END();
   }
   ANNOTATE_SITE_END();
   ANNOTATE_CLEAR_USES(&watch);
}
This example reports all places that use the memory location referenced by
watch
 during the call to
watch_memory()
.
Possible Correction Strategies
To use
ANNOTATE_OBSERVE_USES
 to help you correct an incidental sharing problem, do the following to mark places where you may be able replace uses of a shared memory location with uses of a non-shared memory location:
  1. Add an
    ANNOTATE_OBSERVE_USES
     annotation to the task.
  2. Find all uses of the shared memory location in the dynamic extent of the task.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.