Re: Tuning for PostGreSQL Database

From: Tom Samplonius (tom_at_sdf.com)
Date: 07/26/03

  • Next message: Terry Lambert: "Re: Tuning for PostGreSQL Database" 
    Date: Fri, 25 Jul 2003 21:56:08 -0700 (PDT)
To: Terry Lambert <tlambert2@mindspring.com>

    On Fri, 25 Jul 2003, Terry Lambert wrote:

    > Christopher Weimann wrote:
    > > So I have conflicting documentation.
    > >
    > > I have machine with 4Gig of ram. What is the maximum
    > > value of SHMMAX on FreeBSD?
    >
    > Ideally, you would use memory mapped files for this, and not System V
    > shared memory, so that the OS could implement swapping policies as it
    > saw fit, and could actually swap the data, if nevcessary, instead of
    > it sucking up huge amounts of wired memory.

      PostgreSQL is from the good old days of RDMSes when the they would
    System V shared memory for everything, and store databases on raw devices
    in an effort to utilize as little of the OS as possible, in effort to be
    fast and reliable.

      But it does give PostgreSQL the advantage of working with large tables
    and databases. Mmapping a file over 4GB in size would likely exhaust the
    VM on a x86. Or, is it possible to map 4+GB with PAE?

    > In any case, POSIX deprecated SysV shared memory years ago, and
    > recommends that all code utilize shm_open instead, these days, if
    > you insist on using an interface that sucks up huge amounts of
    > wired pages and KVA space.
    >
    > -- Terry
    >
    >

    Tom

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  • Next message: Terry Lambert: "Re: Tuning for PostGreSQL Database"

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