linux memory

From: utkanbir (hopehope_123_at_yahoo.com)
Date: 07/29/04

  • Next message: gordian: "Re: gethostbyname problem" 
    Date: 28 Jul 2004 23:46:44 -0700

    Hi

    This is related to linux / oracle , i have asked this question to
    oracle support also .

    My box is hp , redhat linux advanced server 2.4.18-e.37smp , 4 itanium
    64 cpus , 8gb.ram and oracle 9.2.0.5 with rac (2 nodes) . I use ocfs ,
    this is a tb.level datawarehouse . My question is related to memory
    usage of linux.
    Although i have 8gb. of ram , oracle shared memory is about
    1.6gb.(ipcs) . My swap size is 24gb. When i check the system by using
    top , etc.... , i see most of the memory is used , and a great amount
    of memory is used by linux for disk cache. This is the /proc/meminfo
    output:
    total: used: free: shared: buffers: cached:
    Mem: 8490827776 6121046016 2369781760 0 29163520 1254342656
    Swap: 25165725696 1141850112 24023875584
    MemTotal: 8291824 kB
    MemFree: 2314240 kB
    MemShared: 0 kB
    Buffers: 28480 kB
    Cached: 1040144 kB
    SwapCached: 184800 kB
    Active: 3157680 kB
    Inact_dirty: 401984 kB
    Inact_clean: 16656 kB
    Inact_target: 715264 kB
    HighTotal: 0 kB
    HighFree: 0 kB
    LowTotal: 8291824 kB
    LowFree: 2314240 kB
    SwapTotal: 24575904 kB
    SwapFree: 23460816 kB
    Committed_AS: 16057008 kB
    HugePages_Total: 0
    HugePages_Free: 0
    Hugepagesize: 262144 kB

    Look at the cached value , here it is about 1gb, , this number reaches
    up to 6gb. I read some articles about linux memory management ,which
    says such a thing is expected behaviour for linux (if there is memory
    use it instead of waste) . But the value increase too much that the
    machine starts paging. (look at the swap values above) And most
    importantly , i use ocfs which uses direct io , so do i get any
    benefit of this linux disk cache? (since direct io does not use any os
    buffer ) Why does linux incrase the cache size too much and than
    starts paging? Whats the benefit of swapping ? Why does not linux
    prevents allocation of cache memory and stop swapping?

     Kind Regards,
    tolga

  • Next message: gordian: "Re: gethostbyname problem"

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