Just did an upgrade from 4.11 to 5.0rc5 on a RB750G and noticed that the CPU is 98-100% all the time. There is no traffic passing while this is the case. No VPN, no proxy, simple ruleset, two queues that are idle.
Any ideas ?
I noticed there is a firmware update available from 2.25 to 2.28
Cheers.
Yes, I would try to upgrade the firmware and see if it makes any difference. If it doesn’t, what does the top command reveal? If all else fails, send a supout to support.
maybe you have proxy or dude package installed?
Noticed this release has similar effect on RB600 - CPU usage has jumped from approx 30% average to 75% despite no other changes
rc5 has the profiler tool. go and see what exactly consumes the CPU
A process called ‘idle’ seems to be using 50-75% of resources. What is that?
idle means that such amount of CPU is available for use (not used)
Seems like the Dude is seeing available resources as CPU usage perhaps?
Seems counterintuitive to show available resources as a resource being consumed then, doesn’t it?
I’ve no idea which OID other than the standard probe that the Dude makes on a Mikrotik device. How can I find out?
Actually comparing CPU in Winbox and the Dude shows the same pattern - so its not the Dude…
Ok I will test.
The Profiler shows total of 100%. For example 30% used, 70% idle. Basically this means that you don’t have to calculate how much free resources you have left if you are using 67.33% of the CPU time 
That is standard way to display resources, nothing that we invented.
Thanks Normis
It looks like CPU figure is showing total of profile but maybe should be subtracting the idle component.
interesting screenshot:
Can you show me a screenshot with the Dude showing a different CPU usage than Winbox profiler? I can’t find any differences (other than slow update speed in the Dude) but maybe I’m looking in the wrong place.
I looked at the profiler and it showed SNMP and management were eating up all my CPU. I removed the SNMP settings and the CPU usage dropped to 1%. I then re-enabled SNMP and it remained at 1%.
Thanks for all the help and suggestions.
well, you will use a rubbish OS! 
I can confirm that rc5 is eating up 100% of the CPU … it doesn’t always happen, but when it does, it stays like that for hours.
This is a new rc5 installation on dual core x86 (2x1.8Ghz) with no traffic at all.
The idle process shows 50% utilization, but that’s only because of the dual core … one of the cores is at 100% and it is not illusion or false 100% representation. The CPU does heat up and the cooling fan goes into a higher RPM.
Geza
as you can see, apart from idle, you have management and unclassified. send supout.rif file to support and we will see what is that ‘unclassified’ process.
My have a same problem. Sometimes CPU usage 100% and it continues about 2 minutes. When I disable SNMP, CPU usage decreases to 20%. It happens every 20minutes. What is that management? I have 2pcs RB1000 V5.0rc4. All RBs have same problem.
[otgonkhuu@MobiNetAU] > tool profile duration=10
NAME USAGE
pppoe 0.5%
www 1.5%
ppp 0.5%
ethernet 4.5%
console 0%
dns 0%
traffic-flow 0.5%
firewall 12.5%
winbox 0%
logging 1.5%
management 64.5%
dhcp 0.5%
profiling 4%
queuing 4%
routing 0.5%
unclassified 5%