NtopNG and General Latency
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I have been running the latest NtopNG for quite a while now (using my own guide as posted here on the forum). Everything works very well and the 5.3 build of NtopNG is infinitely more usable (bugfree) than the current 5.0.xxxx in the official pfSense NtopNG package.
But there is one little issue I cannot quite find the root cause to.
When NtopNG is active/loaded, my gateway RTTsd increases quite a lot. My general gateway ping time with NtopNG stopped is 4.3ms and it has a very solid RTTsd of 0.1ms.
Once NtopNG is active the ping time is pretty solid aroung 4.4ms, but the RTTsd is all over the place (between 5 -> 12ms).It seems this happens because with apparantely random intervals the ping time increases to a larger double digit ms latency.
I get that NtopNG does packet capture and processing - and thus increases latency a little, but this seems wrong.
A can’t remember if the original NtopNG 5.0.xxx package showed this issue, but i believe not.
Is there any further dignostics I can do to find a solution to how I can alleviate this latency increase?
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@keyser Hmm I seems the original NtopNG package for pfSense also comes with the latency penalty - so it’s not related to NtopNG 5.3 and my tweak to get that installed.
What are possible reasons for the occational high latency ping when NtopNG is running? Is it just the packet capture overhead - whenever it does some maintenance job, restarts the capture session or what not?
Or could it be hardware offload or perhaps a 22.01/2.6 specific issue? -
@keyser Bump - No one has any insights on this?
How about some more confirmations/debunkings of my observation that NTopNG always incurs this rather large RTTsd latecy issue on pfSense?
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@keyser If I had to guess, I'd say it has something to do with ntop putting all your interfaces into promiscuous mode. I'm sure someone who knows more about the FreeBSD internals could elaborate, but if you're not seeing very high CPU/interrupt usage, then that would be my guess. What kind of NICs are you running?
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@luckman212 said in NtopNG and General Latency:
@keyser If I had to guess, I'd say it has something to do with ntop putting all your interfaces into promiscuous mode. I'm sure someone who knows more about the FreeBSD internals could elaborate, but if you're not seeing very high CPU/interrupt usage, then that would be my guess. What kind of NICs are you running?
Yes I agree. But would be nice to have confirmation that this is not a 22.01 specific issue. I can’t recall if I observed such a noticable latency penalty back in the 2.4.x days when testing NtopNG.
Th SG-6100 is running Intel IX and IGC driver based Intel Nics only.But I see the same on my SG-2100 with its Broadcom MVNETA driver based Nic.
