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English Forums => Hardware and Performance => Topic started by: thelittleblackbird on June 26, 2026, 10:52:00 PM

Title: latencyspikes of seconds (<3s) during speed test on an atom E3940
Post by: thelittleblackbird on June 26, 2026, 10:52:00 PM
Hi all,

I think i tried to debug it until the  limit of my knowledge but i reached a point i will need a bit of support and guidance.

During a regular speed test via internet (a 350mbps connection) i realized that the "swi1: netisr" routines take 100% of the cpu, this is only noticeable if the FW is enabled, if the FW is disabled then the cpu usage for the same test is not going beyond 18% (the expectation here)

i dont have any idp/ids active, my services are limited to DNSmasq, unbound and tailscale and the nic are intel. so I am out of ideas.

could somebody be so kind to point me to where to look to see where the problems is originated?

thanks in advance
Title: Re: latencyspikes of seconds (<3s) during speed test on an atom E3940
Post by: pfry on June 27, 2026, 12:33:13 AM
An interrupt handler (https://man.freebsd.org/cgi/man.cgi?query=swi&apropos=0&sektion=9) issue? I haven't seen one myself. Do you have any unusual sysctls (tuneables) configured?

Can you paste a "top" capture?
Title: Re: latencyspikes of seconds (<3s) during speed test on an atom E3940
Post by: thelittleblackbird on June 27, 2026, 12:42:34 AM
here you have it, in the attached file.

I tried to implement the tunnable described in the opnsense documentation about performance:
https://docs.opnsense.org/troubleshooting/performance.html (https://docs.opnsense.org/troubleshooting/performance.html)

if you need something else just ask

thanks

Title: Re: latencyspikes of seconds (<3s) during speed test on an atom E3940
Post by: pfry on June 27, 2026, 02:27:25 AM
Huh. Stalling on interrupts (95%). Are you using Realtek Ethernets with the factory (not the plugin) driver? If so, try the plugin. If not, what Ethernet interfaces do you have?