On Thu, 2 Jun 2005, Singh, Vijay wrote:
Hello, I am trying to run network benchmarking using netperf. I have a snapshot of "systat -vmstat 1". Is it OK to see those large number of interrupts (~ 1998) for the lapics?
That's a property of the increase in HZ to 1000 from 100, and that on 6.x, each lapic generates HZ interrupts/sec to the individual processors, rather than the programmable timer deliverable at HZ to a particular (or round-robin'd) CPU, then that CPU broadcasting the clock tick to the other CPUs using IPIs. The rate you see should be approximately HZ * #cpus, so about 2000 for a dual-processor system (which is indeed about 1998). While lowering HZ will lower the overhead associated with processing timer ticks, it will also reduce timer granularity, which can affect performance in other ways (for example, TCP may behave better with finer granularity timeouts).
One of the things we don't show in vmstat -systat that we probably should is per-CPU IPI rates. I've CC'd John in the hopes of convincing him to add that to his todo list :-).
Robert N M Watson _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-smp To unsubscribe, send any mail to "[EMAIL PROTECTED]"
