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Hi, We have a memory issue on Linux server. When I used top command to check the memory, it shows: top - 18:58:55 up 78 days, 5:25, 2 users, load ...
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  1. #1
    Linux Newbie
    Join Date
    May 2012
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    110

    Memory issue on Linux server.


    Hi,

    We have a memory issue on Linux server.

    When I used top command to check the memory, it shows:

    top - 18:58:55 up 78 days, 5:25, 2 users, load average: 9.97, 7.52, 5.74
    Tasks: 2578 total, 3 running, 2575 sleeping, 0 stopped, 0 zombie
    Cpu(s): 14.4%us, 2.2%sy, 0.0%ni, 61.9%id, 20.8%wa, 0.1%hi, 0.6%si, 0.0%st
    Mem: 49432916k total, 47305400k used, 2127516k free, 518164k buffers
    Swap: 16777208k total, 0k used, 16777208k free, 4960840k cached

    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    31966 root 16 0 14652 3032 808 R 2.3 0.0 0:00.96 top
    7062 oracle 16 0 9875m 22m 18m S 1.3 0.0 48:08.34 oracle
    7177 oracle 16 0 9875m 25m 21m S 1.3 0.1 44:31.37 oracle
    7350 oracle 15 0 9874m 21m 17m S 1.3 0.0 44:36.29 oracle
    7773 oracle 15 0 9875m 26m 21m S 1.3 0.1 48:08.23 oracle
    8140 oracle 15 0 9875m 26m 21m S 1.3 0.1 44:23.34 oracle
    8193 oracle 15 0 9874m 21m 17m S 1.3 0.0 47:48.87 oracle
    5296 oracle 16 0 9921m 63m 21m D 1.0 0.1 29:03.85 oracle

    Mem : 49432916k total
    Used : 47305400k

    AND

    # free g shows:

    [root@dillion ~]# free -g
    total used free shared buffers cached
    Mem: 57 55 3 0 0 5
    -/+ buffers/cache: 49 8
    Swap: 16 0 16


    None of the oracle instances are using more memory.

    Then what could be the problem ?

    Why the memory is showing 55 used out of 57GB ?

    Can anybody help me in this issue ?






    Regards,
    Aparna.

  2. #2
    Super Moderator Roxoff's Avatar
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    I don't think you have a memory issue. Linux will use the available memory to buffer all kinds of things - it's quite a bit quicker than fetching stuff from, or writing stuff to the hard disk.

    Just because the memory commit seems high it doesn't mean it's all in use by active programs. The %MEM column on your top output seems to show very little in active use. Also quite telling is the amount of swap you have in use. Cache memory can be recycled easily by your system, so it's used in preference to swap every time it can. If you have memory issues you'll see your swap filling up. You don't have that.

    I suspect you're asking this because you have performance issues on your server? It looks like your server is heavily laden, you load is between 5 and 9. That's fine if you have 8 or 16 cpu cores - but few desktops have that. You might be suffering from Oracle consuming lots of processor time, manifesting itself by leaving you with a slow or laggy system - you're not out of memory you're out of processor cycles.
    Linux user #126863 - see http://linuxcounter.net/

  3. #3
    Linux Newbie
    Join Date
    May 2012
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    Hi,

    From the below output, Can I know what does each field designates ?

    # free -g
    total used free shared buffers cached
    Mem: 23 15 7 0 0 9
    -/+ buffers/cache: 5 18
    Swap: 7 0 7


    Free : 7 : What does this mean ?

    Cached : 9 : what does this mean ?

    Swap : Total :7 and Free : 7 : What does this mean ?

    Please help me in understanding the memory issues on Linux servers.

    Regards,
    Aparna.

  4. #4
    Super Moderator Roxoff's Avatar
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    Take a look at the manual for free (do 'man free' at the command line). The '-g' option means 'show results in gigabytes. Your output means you have 7 of these available as swap, none are in use and you have a total of 7.
    Linux user #126863 - see http://linuxcounter.net/

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