On 11/18/2018 7:00 AM, Sad Clouds wrote:
I'm developing a small tool that tests memory performance/throughput across different environments. I'm noticing performance issues on NetBSD-8, below are the details:
...
NetBSD and Linux have different versions of GCC, but I was hoping the following flags would keep optimization differences to a minimum:
If you want to rule that out, you could always build the same version of gcc on both. Or even run the linux binary (and libs) on NetBSD.
NetBSD: 16 threads x 1 GiB, using 1 KiB memcpy size, no mlock: Thread 2 preflt=13504.86 msec, memcpy=2874.69 MiB/sec ... Total transfer rate: 5817.56 MiB/sec
What? I think your measurements are a bit off here. There may be a problem with the speed, but if you're measuring the per-thread rate properly then the sum of those should equal your total transfer rate. Are the periods during which each thread calculates its rate very different from the period of the overall test?
Also, your subsequent email about memcpy disassembly does not list the full code for the linux version (the jumps at the start refer to instruction addresses that you don't include), so you can't really compare them. I expect that both implementations have a variety of code blocks to handle different alignments, different supported instructions, etc..
Eric