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  1. #1
    Join Date
    Jun 2004
    Posts
    197

    Upgraded network port and now CPU usage is sky high

    Today I upgraded my dual opteron dedicated server from a 10mbps port to 100mbps. While the number of apache access have dropped by about a quarter my CPU usage has increased also by about a quarter, my CPU is touching on 95-100% now.

    What’s most likely to be the cause?

    What’s also interesting is my network port is only showing 20mbps usage, nowhere near the 100mbps its been upgraded to.

    Thanks

  2. #2
    Join Date
    Oct 2002
    Location
    Manchester, UK
    Posts
    1,164
    Whats the result of
    mii-tool -v -v
    Rob Greenwood
    RedHat Certified, Unix Consultant
    http://www.linkedin.com/in/bilco105

  3. #3
    Join Date
    Jun 2004
    Posts
    197
    thanks 4 the reply, here are the results:

    [[email protected] ~]# mii-tool -v -v
    eth0: negotiated 100baseTx-FD, link ok
    registers for MII PHY 1:
    1000 796d 0020 6162 05e1 41e1 0005 2001
    0000 0300 0000 0000 0000 0000 0000 3000
    0001 0301 0000 0000 0000 0018 0000 0003
    7077 8514 0000 ffff 0000 4463 0000 0000
    product info: vendor 00:08:18, model 22 rev 2
    basic mode: autonegotiation enabled
    basic status: autonegotiation complete, link ok
    capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
    advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
    link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
    eth1: no link
    registers for MII PHY 1:
    1000 7949 0020 6162 05e1 0000 0004 2001
    0000 0300 0000 0000 0000 0000 0000 3000
    0001 2001 0000 0000 0000 fff8 0000 0003
    7077 1000 000c ffff 0000 4000 0000 0000
    product info: vendor 00:08:18, model 22 rev 2
    basic mode: autonegotiation enabled
    basic status: no link
    capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
    advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control

  4. #4
    Join Date
    Jun 2004
    Posts
    197
    If it makes any difference I am running php based proxy sites.

    when my port was running on 10mbit my CPU usage at peak times was 65-75%, now I'm on 100mbit its 100%

  5. #5
    Join Date
    Oct 2007
    Location
    Northampton, UK
    Posts
    553
    If the CPU was at 65% serving up on a 10mb link it seams feasible that pushing 20mb would max it out?

    Have you tried running 'top' to see what processes are using the CPU?

    Matt
    SysAdminMan - Asterisk PBX hosting - FreePBX, A2Billing and Elastix

  6. #6
    Join Date
    Jun 2004
    Posts
    197
    This would be true, and its what I first thought, except my apache access have gone down.... so while my server appears to have less uers on it my CPU usage has gone up by 25%

  7. #7
    Join Date
    Oct 2007
    Location
    Northampton, UK
    Posts
    553
    Is it possible, though, that those users are able to 'do more' because of the upgraded link. They may be able to move between pages quicker, do more searches, request more files ...

    Without knowing what Apache is serving up it's difficult to know.

    Did the actual network card in the server change? (ie could it be loading a different module) or was it purely the link speed? Although I reckon if it's definitely Apache that's causing the high load it not likely to be a network hardware problem

    Matt
    SysAdminMan - Asterisk PBX hosting - FreePBX, A2Billing and Elastix

  8. #8
    Join Date
    Jun 2004
    Posts
    197
    no, the card stayed the same

  9. #9
    Join Date
    Apr 2003
    Location
    Los Angeles, CA
    Posts
    800
    Look at it this way: with 10 Mbps you were maxing out your port so there were more apache processes awaiting the completion of the HTTP transaction. Now you don't have this bottleneck, so the transactions get finished faster and hence fewer apache processes are needed. Yet, you doubled your bandwidth usage so your CPU load will likely increase as there simple is more going on. Makes all perfect sense to me.
    Pings <1 ms, Unlimited Transfer, Lowest Price: http://localhost/

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