ASUS RT-N66U, high CPU usage - is everything working alright?

[envee]

Hello all.

So I recently got an ASUS RT-N66U router with the latest stable Merlin build, 380.57. I noticed that when doing file transfers, my CPU usage gets really high. In the web interface under "Network Map", the System Status shows 90-100% for CPU: Core 1. Is this graph of usage? It's worrisome to me to see it nearly at 100% whenever I am transferring or downloading files at 90mbps, so I wanted to check to see if something was wrong with my router.

I SSH'd in to the router while transferring and ran the "top" command. All processes seem to use a normal amount of CPU usage and the usr, sys, and CPU usage per process statistics are all seemingly normal. However, the sirq % is usually 70%+ while doing these transfers. Is this the same statistic the web interface is showing?

I'm fairly positive the N66U is more than capable of maxing out a 100/10 internet connection, but the seemingly high CPU usage is worrying me that it might be bottle-necking since it plateaus in the 90's for percentage on the web interface. The N66U should be able to handle higher speeds than I currently have, or at least I thought.

The weirdest thing though is that the CPU load average is 0.01/0.07/0.1 on the "Tools" page, which is normal, yes?

I have IP Traffic Monitoring On, QOS and most USB and sharing services off, other than the Traffic Monitoring logging to the USB drive. Is the Traffic Monitoring and forcing the router to use software NAT what is causing this? Would turning it off so I can use hardware NAT improve CPU usage in this regard? If so, that is a solution but is definitely not preferred because I really like what the Traffic Monitoring per devices does for me.
Thanks so much in advance for assistance. I'm somewhat of a beginner to networking and router firmware and wanted to make sure my router is functioning properly since it is only a few days old.

*Edit* Upon further investigation, my CPU load in the web interface looks like this during a full file transfer at 90mbps: 1.74, 0.81, 0.32.

 

[bbunge]

I just finished replacing the external USB drive on my N66R (which is the same as the N66U) and I'm running a fresh install of 380.57. While transfering 400 GIG of data back to the drive I've noticed the same load. I'm not having any issues now that I have a good hard drive in my USB enclosure!

 

[envee]

I just finished replacing the external USB drive on my N66R (which is the same as the N66U) and I'm running a fresh install of 380.57. While transfering 400 GIG of data back to the drive I've noticed the same load. I'm not having any issues now that I have a good hard drive in my USB enclosure!

Hmm. The thing is, it's not for USB transfers though. Any heavy internet traffic brings about the high(?) CPU usage for me, on 380.57. Not sure. I turned off IP Traffic Monitoring and re-enabled the hardware acceleration for the switch, and that seems to have made it so it maxes out at 80% usage instead of 100% under heavy load, but I already miss what the IP Monitoring gave me.

 

[gffmac]

How do you disable traffic monitor, don't see an off button

Sent from my HTC One M9 using Tapatalk

 

[envee]

How do you disable traffic monitor, don't see an off button

Sent from my HTC One M9 using Tapatalk

I meant I disabled the IP Monitoring that Merlin's build adds, it's under "Tools > Other Settings > Enable IP Traffic". I wish I could figure out a way to reduce the CPU load/usage and keep this enabled, it's quite nice. As far as I'm aware the basic Traffic Monitoring included in stock/Merlin's firmware can't be disabled though

 

[Eugeny]

Hi all!
I have installed 380.57 on my RT-AC68U and feel performance drops. When I checked web interface I see almost 100% CPU1 load, under torrents load. Before this firmware, with older ones ,I don't saw such big CPU load and don't have any performance issues. I started to disable functions step by step and when I disable router Firewall CPU load dropped dramatically and performance restored!

So, maybe there is some bug in this firmware which cause abnormal CPU load on usual workload? If you have this on another router model too.
And why it helps with deactivating firewall?

 

[Nullity]

Maxing out the wireless throughput capabilities of the router creates massive amounts of software interrupts (sirq). Nothing abnormal about it.

I get ~180Mbit WiFi speeds out of my RT-N66U with 2x2 clients (not 3x3, which the RT-N66U is capable of).

 

[envee]

Maxing out the wireless throughput capabilities of the router creates massive amounts of software interrupts (sirq). Nothing abnormal about it.

I get ~180Mbit WiFi speeds out of my RT-N66U with 2x2 clients (not 3x3, which the RT-N66U is capable of).

Just out of curiosity, when you're hitting that high throughput on your wireless are you seeing 100% CPU load on the web ui?

I'm still getting 100%, even with ethernet connections and not using wireless at all. Including the software interrupts (sirq) hitting ~90%. When I disable the IP Traffic Monitoring and re-enable hardware acceleration it seems to help a bit. When maxing my internet line's throughput either wireless or wired it maxes out at about 70% CPU usage. So it seems like the bottleneck is definitely software navigating of that much throughput versus the hardware. I'm just worried that if my ISP increases my speeds in the near future that this router is already maxing out its capabilities. Then again, if you have a 180Mbit line and it is working for you, that is reassuring. I only have 100/10, but like I said it's hitting 80% load even with hardware acceleration on.

 

[Nullity]

Just out of curiosity, when you're hitting that high throughput on your wireless are you seeing 100% CPU load on the web ui?

Yeah.

I'm still getting 100%, even with ethernet connections and not using wireless at all. Including the software interrupts (sirq) hitting ~90%. When I disable the IP Traffic Monitoring and re-enable hardware acceleration it seems to help a bit. When maxing my internet line's throughput either wireless or wired it maxes out at about 70% CPU usage. So it seems like the bottleneck is definitely software navigating of that much throughput versus the hardware. I'm just worried that if my ISP increases my speeds in the near future that this router is already maxing out its capabilities. Then again, if you have a 180Mbit line and it is working for you, that is reassuring. I only have 100/10, but like I said it's hitting 80% load even with hardware acceleration on.

 

[A.D.]

So I recently got an ASUS RT-N66U router with the latest stable Merlin build, 380.57.

If you scan through the forum here, you'll notice that some strange things can occur with a 380 firmware on a 66 device. I reverted to merlin 378.56.2.

I noticed that when doing file transfers, my CPU usage gets really high..

The 66 devices have a single-core 600 MHz CPU. It is required especially for things like WiFi encryption, VPN, and presumably also PPPoE aka WAN. In a test conducted in 2014 by a serious magazine, the RT-AC66U (first hardware revision and initial firmware) had by far the worst PPPoE WAN performance of all 13 tested models, with the majority of models (including Archer C7) being around four times faster.

In my view, today, the ASUS 66 devices are excellent budget access points and media servers. But if you want routing and higher performance WAN, you should at least go for a 68, although you sound as if even that might not meet your expectations.

I'm super happy with the AC66 as an access point but I let my router do the serious stuff.

 

[BanksiaBoy]

I was having same problem on my RT-AC66U running 380.58_0.
I shut it down, removed the USB disk, restarted and now its running at less than 5%.

Before shutting down, need to unmount the disk.
Does anyone know what happens to file-system on external drive during reboot?

Checking disk now on PC

 

[BanksiaBoy]

I have been having same problem with external USB HDD on my RT-AC66U running 380.58 causing the CPU to run at 100%. If I ran router without the disk CPU ~4%.
I assumed it was because the disk (formatted ext3) was having problems, so I removed it and fsck on ubuntu 14.04. There were some minor errors.

Re-attached to router and restarted. Same CPU issue. Unmounted the disk from the network map USB GUI. Noting that the mount-point directory did not exist before the remount. I created the directory with mkdir, and remounted the USB HDD then re-mounted it from the command-line.

The CPU now runs at ~4%

Question: Are we all reporting high USB/CPU usage from the web GUI? because if after reboot I am on ssh command-line running 'top' -

• If the web GUI is running CPU is at 98 %
• If I am logged out from the web GUI falls back to ~1%

Therefore I suggest that there is some refresh/USB/GUI problem.

 

[oshunluvr]

I noticed the same issue as the above poster - 100% CPU usage since the upgrade to 380.58. Taking a hint from BanksiaBoy, I allowed my RT-AC66U to run a "Health Scan" on my USB drive. After the scan completed, my CPU relaxed to 4% and has stayed in that area for a couple days. My disk is ntfs and the scan was clean.