Messages in this thread | | | Date | Tue, 13 Aug 2002 14:24:54 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] NUMA-Q disable irqbalance |
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On Tue, 13 Aug 2002, Martin J. Bligh wrote: > > 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.
The 1000Hz thing came much later, and I never noticed any impact of that on my machines.
(Note that this is all entrely subjective. I was very disappointed in the feel of the first HT P4 machine I had for the first few weeks, but apart from running lmbench - which looked ok even though it shows that P4's are bad at system calls - I've not actually put numbers on it. But my feeling was that the irq thing made a noticeable difference. Caveat emptor - subjective feelings are not good).
> 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.
The rebalancing was certainly done with a 100Hz clock, so yes, it might have become much worse lately.
Linus
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