Messages in this thread | | | Date | Tue, 13 Aug 2002 13:42:12 -0700 | From | "Martin J. Bligh" <> | Subject | Re: [PATCH] NUMA-Q disable irqbalance |
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>> On a collection of networking workloads the P4 is about 5% better >> performing with the irq balancer off. > > Hmm. And I could _feel_ how my dual HT P4 was slow before the irq issues > were fixed. > > Now, there have been other changes too - like the scheduler (and my > current P4 has a different SCSI interface), but I dunno. The thing I > attributed the improvements in interactive feel was the fact that the work > got balanced out more sanely.
Was that before or after you changed HZ to 1000? I *think* that increased the frequency of IO-APIC reprogramming by a factor of 10, though I might be misreading the code. If it does depend on HZ, I think that's bad.
People in our benchmarking group (Andrew, cc'ed) have told me that reducing the frequency of IO-APIC reprogramming by a factor of 20 or so improves performance greatly - don't know what HZ that was at, but the whole thing seems a little overenthusiastic to me.
M.
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