Dual GPU cuMemGetInfo

Accelerated Computing CUDA CUDA Programming and Performance
1

I’m working with a GTX 295 and trying to get the free memory for both devices.

However when I call cuMemGetInfo(free,total) I am getting exactly the same number of bytes for both devices, implying that it is infact only returning the value for one of them.

I call the routine below from independent threads which have had the ‘gpuIdx’ enumeration passed to them

void createContext(int gpuIdx)
{
int free;
int total;
CU_SAFE_CALL_NO_SYNC(cuDeviceGet(&dev[gpuIdx],gpuIdx));
CU_SAFE_CALL_NO_SYNC(cuCtxCreate(&ctx[gpuIdx],CU_CTX_SCHED_AUTO,dev[gpuIdx]));

            fprintf(logFile,"Created Context %10.10i	%10.10i\n",(gpuIdx),ctx[gpuIdx]);fflush(logFile);

CU_SAFE_CALL_NO_SYNC( cuMemGetInfo(&free, &total) );

fprintf(logFile,"MemInfo	%10.10i	%10.10i	%10.10i\n",gpuIdx,dev[gpuIdx],free);fflush(logFile);

}

the printout looks like this

Created Context 0000000001 0472689488
Created Context 0000000000 0472687408
MemInfo 0000000001 0000000001 0823947264
MemInfo 0000000000 0000000000 0823947264

2

Looks like it works fine for 32-bit Server 2003, but not 64-bit Server 2008 R2.

If I place another seperate video card in (9500GT) I can see a total of three devices, with the two GTX295 GPUs showing exactly the same memory usage and the 9500GT showing different.

So I suppose it is working, but how can the two GTX295 devices be using the EXACT same amount of memory down to the byte?

and only in the 64-bit version, under 32-bit windows they show different amounts.

I should note that the 32-bit and 64-bit versions are run on two seperate machines with two different GTX295s of identical brand and model.

3

Looks like it works fine for 32-bit Server 2003, but not 64-bit Server 2008 R2.

If I place another seperate video card in (9500GT) I can see a total of three devices, with the two GTX295 GPUs showing exactly the same memory usage and the 9500GT showing different.

So I suppose it is working, but how can the two GTX295 devices be using the EXACT same amount of memory down to the byte?

and only in the 64-bit version, under 32-bit windows they show different amounts.

I should note that the 32-bit and 64-bit versions are run on two seperate machines with two different GTX295s of identical brand and model.

4

Just to be extra sure, can you allocate some memory on only one of the GPUs before calling cuMemGetInfo on the 64-bit system?

5

Just to be extra sure, can you allocate some memory on only one of the GPUs before calling cuMemGetInfo on the 64-bit system?

6

Yeah already tried that, it still says the same for both devices. No matter which of the three devices I allocate on, the two GTX 295 GPUs always read the same.

7

Yeah already tried that, it still says the same for both devices. No matter which of the three devices I allocate on, the two GTX 295 GPUs always read the same.