Hi,
Do we have any knobs in FreeBSD to reduce the interrupt latency? I am
currently seeing performance differences between 8.x and 7.x. Anyone have any
ideas?
--HPS
On Wednesday 04 March 2009, Artyom Mirgorodsky wrote:
quoted text > >Repeat the same test using FreeBSD -current.
> >
> >a) On the machine where it is slow.
>
> vmstat -i ; sleep 1 ; vmstat -i
> interrupt total rate
> irq1: atkbd0 233 2
> irq14: ata0 85 0
> irq16: vgapci0 5377 52
> irq21: hdac0 ohci0 742 7
> irq22: nfe0 ehci0 23610 229
> irq23: atapci1 5405 52
> cpu0: timer 203959 1980
> cpu1: timer 200914 1950
> Total 440325 4275
> interrupt total rate
> irq1: atkbd0 234 2
> irq14: ata0 85 0
> irq16: vgapci0 5439 52
> irq21: hdac0 ohci0 742 7
> irq22: nfe0 ehci0 24621 236
> irq23: atapci1 5405 51
> cpu0: timer 205981 1980
> cpu1: timer 202937 1951
> Total 445444 4283
>
> >I think the reduced performance can be explained by a clamp on the
> > interrupt rate around 1000 interrupts per second instead of 8000. Maybe
> > someone has an explanation for this?
>
> You right, the interrupt rate around 1000 (1011) on this machine, but on
> FreeBSD 7.1 more 3000. If it is some kind of interrupt aggregation, may be
> I can try to turn it off?
>
> >b) On the machine where it is fast.
>
> vmstat -i ; sleep 1 ; vmstat -i
> interrupt total rate
> irq4: uart0 4154 0
> irq14: ata0 472922 0
> irq15: ata1 26 0
> irq18: em0 752711 0
> irq21: ahc0 53 0
> irq23: ehci0 103456 0
> irq24: em1 147 0
> cpu0: timer 1551216517 2000
> cpu1: timer 1551195251 2000
> Total 3103745237 4001
> interrupt total rate
> irq4: uart0 4154 0
> irq14: ata0 472923 0
> irq15: ata1 26 0
> irq18: em0 752713 0
> irq21: ahc0 53 0
> irq23: ehci0 110949 0
> irq24: em1 147 0
> cpu0: timer 1551218551 2000
> cpu1: timer 1551197285 2000
> Total 3103756801 4001
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