Kernel [memory] tweaking question

ray_at_redshift.com
Date: 04/05/05

  • Next message: Alex Burke: "Boot0 on boot floppies and 2.88meg drives/controllers" 
    Date: Tue, 05 Apr 2005 05:26:01 -0700
To: freebsd-hackers@FreeBSD.ORG

    I'm doing some tweaking on my kernel tonight (FreeBSD 5.3) and I'm trying to get
    a better grip on what the following lines do and what impact they could have to
    the overall performance of a server:

    options SHMALL=
    options SHMMAX=
    options SHMMAXPGS=
    options SHMMIN=
    options SHMMNI=
    options SHMSEG=

    I understand these control shared memory and how many semaphores the kernel can
    allocate, but I guess what I'm not 100% clear on is how the kernel uses these
    resources when it comes to running something like Apache or MySQL on a heavily
    loaded server. In other words, for something like Apache, how much shared
    memory is required? Or what would adding additional shared memory and/or
    semaphores provide. Does the default # provided for by FreeBSD create a problem
    and/or would it use additional ram if allocated?

    Is there the anyone on the list that has experience with changing these that can
    provide a clear, down to earth explanation as to their impacts? Just hearing
    "you get more memory" doesn't really explain what the OS can do with it, or what
    not having enough could limit, etc.

    Thanks!

    Ray

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  • Next message: Alex Burke: "Boot0 on boot floppies and 2.88meg drives/controllers"

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