rt-1900u NAT testing and CPU load

[carpov alexandru]

I am testing wan speed on a gigabit network while activating different options in the router. Here is what I got so far:
- about 920 mbs while no options are active
- activating web traffic monitor results in a 40-50 mbs speed drop
- activating parental controls results in a 50-60 mbs speed drop
- activating aiprotection results in 10-20 mbs speed drop

I am getting as low as 400 mbs speed if I activate multiple options on the router. Anything that has to do with traffic analysis seems to burden the CPU and it can't NAT at maximum gigabit speed anymore. Core 0 seems to do all the work, while core 1 is at 10%. I am on the latest Asus firmware but I am thinking on going Merlin.

 

[Val D.]

I am on the latest Asus firmware but I am thinking on going Merlin.

What you see is a normal behaviour. Expect similar results with Asuswrt-Merlin firmware. This is what the router is capable of.

 

[carpov alexandru]

This is what the router is capable of.

Well, since the router is not using the dual core cpu at it's fullest, doesn't it mean that with better core management, the results will be better? When there is no device connected to usb , why not use both cores for NAT? My old tplink n750 didn't seem to be affected by options I toggled on. It had consistent speed.

 

[Grisu]

correct but we cant change the world and Asus probably wont do it too.

 

[Val D.]

It had consistent speed.

Gigabit consistent speed?
Does it have any of the options mentioned above?

 

[carpov alexandru]

correct but we cant change the world and Asus probably wont do it too.

i sense hostility and i don't know why. i was just hoping that merlin balanced the CPU usage properly. i don't see any reason why 1 core is at 100% and the other (the one that manages USB) is unused.
i bought this router because it had lots and lots of options but i am sad i can't turn them on since i am losing bandwith if i do.

 

[RMerlin]

When there is no device connected to usb , why not use both cores for NAT?

Because that is not a multi-threaded operation. Multiple cores in a computer won't automatically double the CPU bandwidth - you need to have multiple processes to be able to run things concurrently. The firmware already does what it can to balance things (running OpenVPN instances or Samba on a different core), but that kernel code cannot be "split" between multiple cores.

 

[carpov alexandru]

Because that is not a multi-threaded operation. Multiple cores in a computer won't automatically double the CPU bandwidth - you need to have multiple processes to be able to run things concurrently. The firmware already does what it can to balance things (running OpenVPN instances or Samba on a different core), but that kernel code cannot be "split" between multiple cores.

Ok, that seems reasonable. Is AiProtection runing on core 0 or core 1? Using this logic, everything that is not NAT related should run on core 1, not 0, right? Even parental controls.
sorry if i ask too many questions, i'm just trying to understand.
My old wrt 4300 is having similar wan/lan performance and it's 6 years old. I just flashed it with custom firmware and it achieves 800mbs with an average 32% cpu load. It's curious that my asus router stays at 100% load and is just a bit faster.
I'm sorry, this is not a support forum. I'll show myself out.

 

[RMerlin]

Ok, that seems reasonable. Is AiProtection runing on core 0 or core 1?

AiProtection is implemented as a kernel module. As far as I know, there's no enforced affinity, it depends on the process accessing that module.

 

[Val D.]

My old wrt 4300 is having similar wan/lan performance and it's 6 years old. I just flashed it with custom firmware and it achieves 800mbs with an average 32% cpu load.

Turn on something that does packet processing and it will slow down to 200Mbps and below, like QoS on DD-WRT, for example. The more load you put on the CPU, the less throughput is expected. Even newer ASUS router models with 1.8GHz ARM v8 cores can't process Gigabit traffic with AiProtection and QoS enabled.

 

[Makaveli]

Turn on something that does packet processing and it will slow down to 200Mbps and below, like QoS on DD-WRT, for example. The more load you put on the CPU, the less throughput is expected. Even newer ASUS router models with 1.8GHz ARM v8 cores can't process Gigabit traffic with AiProtection and QoS enabled.

I suggest he stop using AI Protection and switch to Skynet. As for the rest of the options keep them on but don't expect to get the same speed as they were when off.

Even Low level enterprise gear won't give you line speed once you start putting on features that require the CPU to process packets.

If he is looking to have all of that on while keeping gigabit speed you will need to look at building a Quad Core PFsense box with 8GB of ram etc.