On Saturday 04 June 2005 04:02 pm, Robert Watson wrote: > 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).
Actually, the lapic timer runs at hz * 2 on each CPU. The interrupts are local to each CPU though. > 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 :-). Ah yes. -- John Baldwin <[EMAIL PROTECTED]> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-smp To unsubscribe, send any mail to "[EMAIL PROTECTED]"
