topic L5518 CPU in Intel® Moderncode for Parallel Architectures

L5518 CPU

Amal_P — Wed, 09 Feb 2011 08:26:19 GMT

Hi,

My test configuration is,

CPU: L5518
No Of Processors: 2
ie No of Cores is : 4 + 4
ie No of threads with hyperthreading is: 8 + 8 = 16.
RAM: 100GB

The specification page( http://ark.intel.com/Product.aspx?id=40727 ) says that the maximum memory throughput is 25.6GB/s for one CPU of 4 cores. I wanted to measure the maximum memory throughput of my system which is having 8 cores because I've 2 L5518s.

The test I done is,

Launched 16 threads and set each thread's affinity to unique CPU number.
Allocated 100MBX2 memory in each of these threads.
Done write to one 100MB. And copy to the other 100MB. Thus, write-read-write.

But the maximum throughput I'm getting is only around 25.5GB/s(Measured with PTU). I expected 50GB/s because I'm having two L5518 processors.

Where am I doing it wrong?

Regards,
Amal

L5518 CPU

Ilnar — Wed, 09 Feb 2011 09:19:14 GMT

try to measure usingbanchmarking tools like sisoft sandra.
there is no any idea until you show your code

L5518 CPU

Amal_P — Wed, 09 Feb 2011 11:06:30 GMT

I want to know the maximum possible memory throughput for L5518 when I have two of those which makes it 8 cores and 16 hyperthreads.

Regards,
Amal

L5518 CPU

Ilnar — Wed, 09 Feb 2011 12:24:31 GMT

25.6Gb/s is the max throughput. real throughput depends on channels count, bus and memory frequency, latency. large amount of core couldmake max workload, there are no linear increasing of the memorythroughput

L5518 CPU

TimP — Wed, 09 Feb 2011 13:43:30 GMT

Quoting ilnarb

try to measure usingbanchmarking tools like sisoft sandra.
there is no any idea until you show your code

For example, we can't see from here whether you set your BIOS to NUMA, if it has such a setting, and whether you set affinity appropriately. You can't expect to beat everyone else by30% without even thinking about your method.