[Gems-users] unexpected results

["Dave Z." <zhu_dave@xxxxxxxxx>]

Hello,

I'm simulating a simple memory benchmark with 2 processors (L1 cache: 64K, L2 cache: 128K). The memory latency (DIRECTORY_LATENCY) is 120. In my benchmark, a data size of 512K is read in every iteration. So, I'd assume ruby cycles should be at least data_size/cache_line_size * DIRECTORY_LATENCY * iterations. For example, it should be at least 98,304,000 cycles for 512K, 64B cache line size and 100 iterations. But the cycles I get is much smaller. Is there any optimization used by Ruby that might cause this?

I've modified Ruby profiler to show cache events for each processor. The number of Other_GETS events on processor1 is larger than the number of loads on processor2, and vice versa. Is this not unusual? Any ideas what might cause this?

Thanks!

Dave




 
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