Why doesn't my threaded .Net app scale linearly when allocating large amounts of memory?

Question

I’ve run into something strange about the effect of large memory allocations on the scalability of the .Net runtime. In my test application I create lots of strings in a tig

Answer 1

The hardware you're running this on is not capable of linear scaling of multiple processes or threads.

You have a single memory bank. that's a bottle neck (multiple channel memory may improve access, but not for more precess than you have memory banks (seems like the e5320 processor support 1 - 4 memory channels).

There is only one memory controller per physical cpu package (two in your case), that's a bottle neck.

There are 2 l2 caches per cpu package. that's a bottle neck. Cache coherency issues will happen if that cache is exhausted.

this doesn't even get to the OS/RTL/VM issues in managing process scheduling and memory management, which will also contribute to non-linear scaling.

I think you're getting pretty reasonable results. Significant speedup with multiple threads and at each increment to 8...

Truely, have you ever read anything to suggest that commodity multi-cpu hardware is capable of linear scaling of multiple processes/threads? I haven't.