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100% CPU usage

Discussion in 'Asuswrt-Merlin' started by Zagg, May 15, 2018.

  1. Zagg

    Zagg New Around Here

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    May 15, 2018
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    Hello all,

    On my RT-AC88U i have 100% cpu when I use arround 200mb/s bandwidth.
    When I run speedtest by example , CPU usage is 100% so max bandwidth is 200-230Mb/s on a 1Gb/s fiber link :(
    On htop "nt_center" process is on the top when I run the speedtest but can't see why CPU is full used.

    When ac88u is on AP mode , speedtest give me 980mb/s
    When ac88u is on router mode, speedtest give me 220mb/s

    Thanks in advance for any help.

    (I use ASUS Merlin v384.5 on ASUS RT-AC88U)

    Davy
     
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  3. joegreat

    joegreat Very Senior Member

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    Stop using CPU-bound functions like AIProtection - in "normal" operation the LAN traffic should bypass the CPU and give you full bandwidth (as you see in AP mode).

    But some function disable the CPU bypassing and the small, poor and slow CPU is fully utilized and show the low(er) throughput as you see in router mode.

    By the way: It could be also WIFI encryption which uses up the CPU power - so better do the speed check on a wired connection! :rolleyes:
     
    Zagg likes this.
  4. Zagg

    Zagg New Around Here

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    Hi,
    Thanks for answer.
    I have disable AIProtection and test from wired connection. I'm now at 300Mb/s on router mode when CPU core 1 is at 100% used.
    Core 2 seems to be unused , don't know if normal.
    Do you know how find the fonction disable CPU bypassing please ?
    Thanks in advance,
    Davy
     
  5. joegreat

    joegreat Very Senior Member

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    The best way would be to login on the router via SSH (need to enable SSH on the Administration page) and use the top command to see the top CPU usage on the router while you do the speed test.
     
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  6. Zagg

    Zagg New Around Here

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    ok thank you.
    When I run a speedtest 2 process are on top :
    28.4% [ksoftirqd/0]
    2% /sbin/netool
    2.1% nt_center

    And idea what is it ?

    Thanks.
    Davy
     
    Last edited: May 15, 2018
  7. ColinTaylor

    ColinTaylor Part of the Furniture

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    Those processes (netool and nt_center) are inconsequential.

    Don't look at the process list. Press "1" and then look at the "CPUn:" lines second and third from the top. Particularly take note of the %idle and %sirq. You'll probably find the your %sirq is hitting 100% for one of the processors.
     
    Zagg likes this.
  8. CaptainSTX

    CaptainSTX Very Senior Member

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    As a point of comparison I am running 384.5 on an AC1900P with the following processes/ service active and 10 -12 devices connected most of which are IoT devices.

    AIprotection ON
    Traffic Monitor ON
    2 Regular SSIDs
    4 Guest SSIDs
    2 OpenVPN clients running
    Hardware Acceleration ON

    With a gigabyte connection my Processor 1 goes 99-100% Processor 2 68-70%

    Speedtest using an Ethernet connected PC to a nearby speed test server 880-920 Mbps down 42 Mbps up
     
    Zagg likes this.
  9. Zagg

    Zagg New Around Here

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    Ok, thanks all for your help.
    After disable AIprotection, traffic monitor ...etc no change in bandwidth.
    After hard reset all is become good ... 950Mb/s down 190 Mb/s up. I don't understand why but for now, all is ok !!!
    I have installed skynetv6 script (only inbound traffic filtered) and no change in bandwidth
    Firewall is on, AIprotection and traffic monitor are off.
    Thanks!

    Davy
     
  10. Beherit

    Beherit Regular Contributor

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    Yeah, something's wrong. I don't think it has anything to with AIProtection being on or off, as I use it and the CPU load on my AC87 is 2-5% during a speedtest @ 1 gbit.

    Unfortunately, hardware acceleration is somewhat of a mystery in the ASUS code. Supposedly my AC87 has support for FA acceleration, but I've never managed to get it turned on, regardless of settings or any combination of them. CTF acceleration works fine out of the box, even when I have traffic analysis and qOS turned on.

    To check if you have hardware acceleration, go to Tools --> Sysinfo in the UI or use get ctf_fa_mode. 0 = hardware acceleration off. 1 = CTF is turned on. 2 = FA is turned on.

    ksoftirqd using up all CPU cycles is the Linux equivalent of svchost.exe doing the same in Windows, ie annoying and takes a long time to fix. ksoftirqd is a kernel thread that offloads system data traffic (it's my own explanation, dont' quote me on that please), when the hardware can't handle having its "channels" saturated. Only thing that can cause this in a router that'd make sense besides hardware NAT acceleration being off, is a faulty (or failing) USB drive with read/write errors that the system tries to work around constantly. If you have any USB drive connected, try removing it if you haven't already.

    Only thing I can think of to fix this, is a thorough and complete troubleshooting. Start off with a factory reset and then apply settings/functions/additions one by one until hardware acceleration stops working. As painstaking and tedious as it is, just to rule out what's causing this.

    If you're using OpenVPN, then such a high CPU load makes perfect sense. :)
     
    Zagg likes this.
  11. Zagg

    Zagg New Around Here

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    Hi,

    thanks for informations. A factory reset and apply previous setting now its workings nice.
    The command get ctf_fa_mode not work. Its a command to use on SSH ?
    Thanks in advance,
    Davy
     
  12. Beherit

    Beherit Regular Contributor

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    Yep, SSH. Sorry about the typo, it's: nvram get ctf_fa_mode
     
  13. ed209

    ed209 New Around Here

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    I was seeing the same performance issue and CPU utilization on my RT-AC5300 even after updating to 384.5 and performing a reset . I associated it to AB-Solution and/or Pixelserv. I was only getting 300Mbps until I did a factory reset and then got my full gig speed. I did this twice (installed AB-Solution and Pixelserv and the same thing happened).

    FWIW - I have Bandwidth Monitor/App Analysis, web history enabled and 1 OpenVPN client configured.

    I can live without AB-Solution.
     
  14. doczenith1

    doczenith1 Senior Member

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    When y'all were getting the slower speeds did you verify that NAT acceleration was enabled?
     
  15. ed209

    ed209 New Around Here

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    Mine is set to "auto"... You could be on to something here... But right now I'm too tired :)
     
  16. CaptainSTX

    CaptainSTX Very Senior Member

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    The switch only has two positions: Disabled or Auto. If the switch is on and CTF is enabled it will tell you in a text field to the right of the switch.
     
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