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changeset 189:91d0d2e06719 false_sharing

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backoff won't be optimized out by gcc
author Merten Sach <msach@mailbox.tu-berlin.de>
date Fri, 03 Feb 2012 17:57:09 +0100
parents c66137e4dc2f
children a8312581709c
files CoreLoop.c MasterLoop.c
diffstat 2 files changed, 23 insertions(+), 11 deletions(-) [+]
line diff
     1.1 --- a/CoreLoop.c	Fri Jan 13 11:49:05 2012 +0100
     1.2 +++ b/CoreLoop.c	Fri Feb 03 17:57:09 2012 +0100
     1.3 @@ -47,6 +47,8 @@
     1.4     int32           numMasterInARow = 0;
     1.5     volatile int32 *masterLock;
     1.6     VirtProcr      *masterVP;
     1.7 +   
     1.8 +   double         workspace1,workspace2; //variables for master lock busy waiting
     1.9  
    1.10     // init random number generator for retries
    1.11     uint32_t seed1 = rand()%1000;
    1.12 @@ -141,11 +143,16 @@
    1.13        while( currVP == NULL ) //if queue was empty, enter get masterLock loop
    1.14         {    //queue was empty, so get master lock
    1.15  
    1.16 -		 if(numMasterInARow > 2){
    1.17 -		 	wait_iterations=(randomNumber(&seed1, &seed2) % (numMasterInARow*numMasterInARow))*100;
    1.18 -	   		int i;
    1.19 -	  	    for(i=0; i<wait_iterations; i++)/*busy wait*/;
    1.20 -		 }
    1.21 +	if(numMasterInARow > 2){
    1.22 +                wait_iterations=(randomNumber(&seed1, &seed2) % (numMasterInARow*numMasterInARow))*100;
    1.23 +	   	int i;
    1.24 +	  	for(i=0; i<wait_iterations; i++)
    1.25 +                {/*busy wait*/
    1.26 +                    workspace1 += (workspace1 + 32)/2;
    1.27 +                    workspace2 += (workspace2 + 23.2)/1.4;
    1.28 +                }
    1.29 +        }
    1.30 +                 
    1.31           gotLock = __sync_bool_compare_and_swap(masterLock,
    1.32                                                  UNLOCKED, LOCKED );
    1.33           if( gotLock )
    1.34 @@ -161,7 +168,11 @@
    1.35  	   wait_iterations=(randomNumber(&seed1, &seed2) % (tries+1))*100;
    1.36  	   //addToHist( wait_iterations, coreLoopThdParams->wait_iterations_hist );
    1.37  	   int i;
    1.38 -	   for(i=0; i<wait_iterations; i++)/*busy wait*/;
    1.39 +	   for(i=0; i<wait_iterations; i++)
    1.40 +           {/*busy wait*/
    1.41 +                workspace1 += (workspace1 + 32)/2;
    1.42 +                workspace2 += (workspace2 + 23.2)/1.4;
    1.43 +           }
    1.44  	}
    1.45  
    1.46           tries++;      //if too many, means master on other core taking too long
    1.47 @@ -199,7 +210,9 @@
    1.48            _VMSMasterEnv->startMaster.longVal = endSusp.longVal;
    1.49            #endif
    1.50            //==================================================
    1.51 -   }//CoreLoop      
    1.52 +   }//CoreLoop
    1.53 +   
    1.54 +   return (workspace1 + workspace2); //gcc fake out for -O3
    1.55   }
    1.56  
    1.57  inline uint32_t

     2.1 --- a/MasterLoop.c	Fri Jan 13 11:49:05 2012 +0100
     2.2 +++ b/MasterLoop.c	Fri Feb 03 17:57:09 2012 +0100
     2.3 @@ -106,7 +106,6 @@
     2.4     slaveScheduler   = masterEnv->slaveScheduler;
     2.5     semanticEnv      = masterEnv->semanticEnv;
     2.6     
     2.7 -      //masterLoopStartPt:
     2.8     while(1){    //switch to core_loop and back to here is at end of loop
     2.9         
    2.10         //============================= MEASUREMENT STUFF =======================
    2.11 @@ -120,10 +119,10 @@
    2.12  
    2.13  
    2.14        //Poll each slot's Done flag
    2.15 -   numSlotsFilled = 0;
    2.16 -   /*
    2.17 +      numSlotsFilled = 0;
    2.18 +      /*
    2.19           Meas_startMasterLoop
    2.20 -    */
    2.21 +      */
    2.22     for( slotIdx = 0; slotIdx < NUM_SCHED_SLOTS; slotIdx++)
    2.23      {
    2.24        currSlot = schedSlots[ slotIdx ];