SUPER weird - AC87R - PC torrent - high router CPU usage - Merlin

[LSL1337]

I'm not a network expert, I can do port forwarding, and set up DNS, but that's pretty much it.

I have an 87R router with Merlin 378.55 (not really up to date, i know)

So, I have a gigabit home connection (1000/200)
I just built a NAS, and noticed a very strange behavior.

It runs unraid and torrent dockers. I tried first Deluge, transmission, rtorrent, everything really. They download to an SSD cache, the torrents are very well seeded on a private tracker, but they would only reach 10 MB/sec, and my router cpu would be around 100% core1, 30% core2, my ping to the local exchange would go from 1-2ms to 30-40-50-70 randomly. The router is a bottleneck.

I have QoS disabled, and hardware NAT enabled.

Here is the weird part. I found qbittorrent, and it reaches 100MB/sec without killing my router.
wow, so i use qbittorrent.

And the weirdest thing still.
I try it on my desktop computer (i7, ssd, desktop), qbittorrent on windows, and it has very similiar performance to the other clients. Around 10-12MB/sec my cpu1 is maxed out at 100%, and my ping skyrockets. So same version of the same client with the same settings on a different platform, and they all hammer the router CPU with HW NAT enabled.

When i run speedtest.net for a close server, sometimes i reach 780-820Mbit downstream, which is basicly the max the router can do according to the excellent review posted on this site. (quite dissappointing btw that my pretty high end router can't even route on wired network more than 800Mbit one way...)

While i run speedtest, my cpu utilization is around 95% on cpu1, and 50-60% on cpu2. it doesn't absolutly maxes out my cpu1, therefor my pings only goes from 1-2ms to 3-4ms which is still very good in my opinion.

SOOO, in conclusion.
The router can do around 800mbit down, even from torrent with pings under 5ms, but only on speedtest or qbittorrent on linux.

If i use any other client on linux, or even the same client on windows, it hammers my cpu1 to 100%, the ping skyrockets, and performance is barely around 10MB/sec (even on SSD). (very few connections, less than 100, according to the review, the router can handle 10000+ easily, if i read it correctly)

I tried disabling the firewall, on or off, didn't change anything, i leave it ON.
My first google query lead me to this forum. I didn't even specify the router name, but the first hit had 87R in the name.
Some guy had the same problem. He was downloading on PC, and his router had 100% cpu utiilization as well.
After turning ON QoS, he said that it fixed his problem.
If i turn on QoS (and HW nat as well) than my speeds even on speedtest stay below 200Mbit.



TL;DR:
Any idea how is that possible that every torrent client hammers my cpu, but qbittorrent on linux has no problem?

my setup: 87R on Merlin 378.55
HW NAT ON
QoS off
Firewall ON (off is the same)

what could be the cause? Please don't write the usual, just update everything, and it may fix your problem, or not, worth a shot, etc etc. It takes a lot of time to set up everything from scratch for possibly no real gain.

 

[pete y testing]

Any idea how is that possible that every torrent client hammers my cpu, but qbittorrent on linux has no problem?

quite poss that the max concurrent connection are set differently as it sounds like your just flooding the nat table

try limiting both the max concurrent connection and the max upload speed on those torrent client apps

just because have mega fast internet doesnt mean the router can handle the load when it comes to the amount of connections

 

[LSL1337]

Thanks for the reply, but i don't see how the same client with the same settings on the same torrent can kill the router at 10MB/sec, and didn't do anything at 10 times the speed, at over 100MB/sec on linux
i don't have max number of connections set up, but the torrent is only connecting to around 30-40 peers, which is basicly nothing (considering concurrent connections)

 

[LSL1337]

so nobody has idea how can less then 100Mbit traffic to 40-60 connections can kill my connection? ok than...

 

[sfx2000]

Any Torrent client can run the NAT tables out of memory due to the number of concurrent WAN side connections.

 

[LSL1337]

Wow, after trying for a week, i finally unlocked the secret )

First of all, it's still not the NAT tables. As i said, the client only connects to around 40-50 peers at best, and qbittorrent managed it fine at 100MB/s (so around 800Mbit/s), but not the windows version, which 100% hammers my router CPU, and brings up ping to 50+ ms (from 1ms)

As it turns out, the two qbittorrent clients weren't configured exactly the same, there is a small, but very important difference.

When i enable uTP mode, it kills my router CPU, and when I disable it, it works fine. (sidenote: this uTP stuff is enabled in most clients by default I think)
I managed to replicate the results in other torrent clients as well (Deluge, utorrent)

Is it expected that uTP connections hammer the router cpu? (I guess it is some torrent protocol, which was made around 2009, to play the ISP throttling, or something, i really don't know.)
I think uTP means, that the torrent clients sends data through UDP, and not TCP.
When it sends data through UDP, it kills (well it's not crashing, but 100% CPU1 is not normal behaviour) my router at around 100-130Mbits (for only 40 connections total), but when i switch it to TCP mode, it works fine, and can NAT around 800Mbit, while my ping stays under 5ms, and very stable.

I really couldn't even tell you the differece between TCP and UDP, but is this normal?
Based on the little I know, it should work the other way even, shouldn't it?
Is this an expected behaviour of the router? Or just a bug in the old version, and it should be fine in the newer releases?
Maybe uTP was made to play the ISP throttle, but was not designed to 100Mbit+ bandwith in mind? Anyone? Maybe the reason it works, that my gigabit ISP doesn't throttle p2p, so TCP is a much better fit for my use case?

Thanks.