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CPU high usage AC1900U/AC68U. VLAN related?

Discussion in 'ASUSWRT - Official' started by webbie, Feb 26, 2020.

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  1. webbie

    webbie Occasional Visitor

    Joined:
    Feb 23, 2020
    Messages:
    15
    Hello!

    I have just installed a AC1900U (AC68U) in my home.

    I’ve carried out a pretty basic installation, 3.0.0.4.384.45717 . A hard reset plus define SSIDs, remove upnp, define some static Ip and that’s all.

    No Aimesh, Ai protection or openVPN.

    The only relevant configuration apart from the basic is that my provider needs to define a triple VLAN (spanish Movistar, in special ISP requisites), so my data goes through VLAN 6, IPTV and VOIP through 3 and 2 (I don’t use these but I have to define them)

    My ISP provider is giving me theoretical 600/600mbps. My tests:

    1) I have 630/630 mbps through LAN. Perfect then.
    2) With wifi, 1m far from router, a 2015 macbook pro (3x3 client presumably), I get up to 400-450mbps. Nice result but I was expecting a Little bit more (around 550-600).

    I’ve seen my CPU usage during the speedtest and notice this:

    1) During LAN test CPU gets to 75-80%
    2) During wifi test CPU gets to 95-100%
    3) 0-2% while not testing.

    So my guess is that wifi is capping at 400-450 because a full CPU usage and not because a wifi limitation.

    My question if this CPU usage is what it should be or it is higher than expected and could be reduced with some clever settings.

    I consider these 3 scenarios:

    1) This CPU usage is fully normal for a AC68U with this data rate. It sounds strange anyway.
    2) There is an extra CPU usage due to VLAN interface. It could be an extra processing load to handle VLAN. Or maybe it is HW and shouldn’t be noticed.
    3) Even with VLAN this is too much CPU usage. In this case, what can I try?

    I’ve seen that I have CTF enabled. Anything else?

    What are your thoughts?

    Thanks!
     
  2. Grisu

    Grisu Part of the Furniture

    Joined:
    Aug 28, 2014
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    3,082
    you could overclock your old 68U from 800 to 1200MHz.
    Is hw-acceleration enabled?
     
  3. webbie

    webbie Occasional Visitor

    Joined:
    Feb 23, 2020
    Messages:
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    Thanks for your quick answer!

    AC1900U is a 1000MHz, isn't it?
    https://www.snbforums.com/threads/rt-ac68u-rt-ac68p-rt-ac1900-rt-ac1900p.35759/

    Anyway before any overclocking, are these CPU usage normal then? I can accept them but I just want to make sure that there is no an underlying problem.

    "Is hw-acceleration enabled?"
    I think so. NAT acceleration = AUTO (CTF enabled)
    Any other setting related to HW acceleration?
    I don't see any of FA option just in case it should.

    Regards!
     
  4. webbie

    webbie Occasional Visitor

    Joined:
    Feb 23, 2020
    Messages:
    15
    Hi again

    I have enabled all IGMP options just in case it has something to do.
    Now I have 480mbps with wifi (100% CPU) and 620 with cable (80% CPU).

    Are these results the expected for a AC68P/AC1900U?

    I've been told that VLAN management is very light and it is unlikely to cause an appreciable increase of CPU.

    So maybe this 100% CPU is what it should be.

    Thanks a lot!
     
  5. Grisu

    Grisu Part of the Furniture

    Joined:
    Aug 28, 2014
    Messages:
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    1900 and 68U/W/R/P and others are the same, they started with 666MHz, later 800 and then 1000.
    But they usually all can run 1200 very well.
    Only 1900P has been slightly different with 1400MHz clock and better chips (but more problems due to it, some compatibility issues).
    https://www.snbforums.com/threads/rt-ac68u-rt-ac68p-rt-ac1900-rt-ac1900p.35759/page-5

    Yes, I meant NAT-accel.
    Do you use USB-storage, this will increase RAM and CPU too.
    Sorry, cant answer the rest as I sold all asus routers due to permanent problems with their firmwares.
     
    Last edited: Feb 26, 2020
  6. ColinTaylor

    ColinTaylor Part of the Furniture

    Joined:
    Mar 31, 2014
    Messages:
    11,054
    Location:
    UK
    Are your CPU figures the combined total of both CPU cores or the figure for a single core? I get the same throughput (adjusting for our different CPU speeds) but that's for a single core. The other core is mostly idle. I don't use VLANs though.
     
  7. webbie

    webbie Occasional Visitor

    Joined:
    Feb 23, 2020
    Messages:
    15
    Hello

    I was reporting just CPU1. My mistake.

    My CPU2 is higher than 60-80%. I guess 100% when max speed is reached… I should have paid more attention to its value.
    Anyway, I've done more tests and I have some striking results. I'll post it separately...

    Thanks!