Maximum kern.hz ?

D

DigiSoft

Can someone tell me what is the maximum allowed value for kern.hz?

Right now I am running it on 2000, what will happen if I set it on 4000?

I have 3 GHz CPU.
 
DigiSoft said:
Right now I am running it on 2000, what will happen if I set it on 4000?
Click to expand...
Earth might blow up.

I'd keep it at 1000 (the default since 8.0), at most. Why did you even set it to 2000?
 
Set it too high, and the kernel will do nothing but service timer interrupts. :)

Timer interrupts fire every 1/HZ seconds. IOW, if you set it to 4000, then 4000 timer interrupts will fire every second.
 
I think I agree with SirDice, keep moving it up until it stops helping. Or as we used to say in the shop: Turn it till it strips and then back it off half a turn.
 
Is there any chance you have enabled polling for your network card(s)?
If so, might want to look into disabling polling, which would make the CPU be interrupted to process network data whenever there's any, as opposed to being interrupted extremely often even when there's nothing waiting. :)
 
DigiSoft said:
Ok but on 2000 my Gaming server was producing 500 FPS and on 4000 it produces about 800 and the lag is lowered.
Click to expand...
At default kern.hz=1000, glxgears was around 4000

sysctl -a | grep kern.hz had this:
Code: 
kern.hz_min: 8
kern.hz_max: 137438
kern.hz: 1000

kern.hz=137438 rebooted fine and glxgears does 7000 😲

I'm on 16.0-CURRENT with Skylake i5-6400T (Intel HD 530)
 
"vmstat -i" will show you total interrupts and rate for various devices. On a pi3 I see things like these!
Code: 
interrupt                                             total       rate
lintc0,1:-ic_timer0                                  945529       1156
lintc0,8: intc0                                    13108691      16020
intc0,17:-x_dwcotg0                                19575428      23923
 
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