[boost] boost 153 interprocess_mutex much slower in windows 7 than xp?

Subject: [boost] boost 153 interprocess_mutex much slower in windows 7 than xp?
From: Noll, Jeffrey T UTAS (jeff.noll_at_[hidden])
Date: 2013-10-07 10:26:32

We have 3 processes that are synchronized with an interprocess mutex. Basically one of them has a multiplier which allows the others to run at a synchronized accelerated rate. Under XP we typically can get it to run at 5000 times realtime. New desktop refreshes are coming out running Windows 7 and the same code with faster machines with more memory are maxing out at 250 times with 95%+ cpu idle time.

Am new to boost so am wondering if we're doing something wrong. Here's the crux of the code. 3 processes and some shared memory.

Share memory defines

       struct ds_control_sync
       {
              boost::interprocess::interprocess_mutex      mutex;                        //Mutex to protect access to the queue
              boost::interprocess::interprocess_condition  cond_running;           //Condition to wait when the control software is running
              boost::interprocess::interprocess_condition  cond_timestep;          //Condition to wait until the control software is to run again
       };

       struct ds_plant_sync
       {
              boost::interprocess::interprocess_mutex      mutex;                        //Mutex to protect access to the queue
              boost::interprocess::interprocess_condition  cond_running;           //Condition to wait when the plant software is running
              boost::interprocess::interprocess_condition  cond_timestep;          //Condition to wait until the plant software is to run again
       };

Control process has a thread that waits for a signal to run once.
DWORD __stdcall Control_Sync (LPVOID)
{
       scoped_lock<interprocess_mutex> lock(sm_control_sync->mutex);
       while (1)
       {
              sm_control_sync->cond_running.notify_one();
              sm_control_sync->cond_timestep.wait(lock);
              ns_common::TimeProfile_Periodic (&sm_io->status.control_sync, &sync_first, &sync_time);
              Control_PWM ();
              if (control_run)
              {
                     Control_Run ();
                     control_run = FALSE;
              }
              else
              {
                     control_run = TRUE;
              }
              ns_common::TimeProfile_Execution (&sm_io->status.control_sync, &sync_first, &sync_time);
       }
}

Plant process has the same sort of thing
DWORD __stdcall Plant_Sync (LPVOID)
{
       scoped_lock<interprocess_mutex> lock(sm_plant_sync->mutex);
       while (1)
       {
              sm_plant_sync->cond_running.notify_one();
              sm_plant_sync->cond_timestep.wait(lock);
              ns_common::TimeProfile_Periodic (&sm_io->status.plant_sync, &sync_first, &sync_time);
              Plant_Run ();
              ns_common::TimeProfile_Execution (&sm_io->status.plant_sync, &sync_first, &sync_time);
       }
}

And then main process counts down a multiplier to increase it's run rate. In this case 10000X

boost::interprocess::scoped_lock<boost::interprocess::interprocess_mutex> plant_lock(plant_sync.mutex);
boost::interprocess::scoped_lock<boost::interprocess::interprocess_mutex> control_lock(control_sync.mutex);

mult = 10000;
if(mult > 1)
{
       iterations = 0;
       while(mult-- > 0)
{
              plant_sync.cond_timestep.notify_one();
              control_sync.cond_timestep.notify_one();
              plant_sync.cond_running.wait(plant_lock);
              control_sync.cond_running.wait(control_lock);
              iterations++;
       }
}

Works great under XP, our new Windows 7 desktops it are dog slow by a factor of around 50. Any ideas why this would be?
Thanks!

Jeffrey Noll
Software Engineer
[phone]

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