Hello all,
I have simulated a 8 cores CMP where consists of 4 chips and each chip has 2
cores and one shared L2. MOESI-CMP-directory is coherency protocol.
Core0 Core1 Core2 Core3 Core4 Core5 Core6
Core7
|------------| |------------|
|---------------| |---------------|
| |
| |
L2 __ Dir0 L2 __ Dir1 L2 __ Dir2
L2 __ Dir3
|-------------------------|--------------------------|-------------------------------|
|
Memory
I have run below application two times. First time, Thread1 and Thread2 are
mapped on two cores 2, 3 (there is a shared L2 between them). In another
run, I have bound these two threads to cores 2, 4 ( L2 is not shared between
them). I have a problem with this application. When number of iteration of
for loop is increased, difference between execution time of run1 and run2 is
increased, too. But, for this application, it's clear that coherency cost
isn't increased when iteration of for loop is increased. Could you tell me
why this happen?
for (i=0;i<5;i++)
{
THREAD1; // thread1 *read* a large array. Size of the array is
smaller than L2 cache.
THREAD2; // thread2 *read* the array that read by thread1
}
Best Regards
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