Re: adding more ram

From: Charles Swiger (cswiger_at_mac.com)
Date: 12/11/03

  • Next message: Arie J. Gerszt: "disk error / failure: need help! (smart failure predicted)" 
    Date: Thu, 11 Dec 2003 13:58:24 -0500
To: freebsd-hackers@freebsd.org, freebsd-isp@freebsd.org

    On Dec 11, 2003, at 12:01 AM, Robert Watson wrote:
    > [ ... ]
    > Actually, the thing I use swap for most now is to make sure I can
    > allocate
    > large temporary file systems without consuming excessive kernel address
    > space. I.e., I'll often create a 512mb swap-backed md device for /tmp,
    > and make sure I have enough swap to fully back it and everything else,
    > even though the chances are I won't touch it in normal operation. I
    > just
    > don't want to run out in the event something does need it...

    I first saw this implemented under Solaris via the "tmpfs" filesystem
    mount type, and I agree with you that it tends to function quite well.
    By the time Solaris transitioned from 2.6 to 2.7 (aka Solaris 7),
    having /tmp be memory-based was the default system configuration, and I
    would like to see FreeBSD pursue the same course.

    I seem to recall that Solaris sets the paging priority of processes
    higher than tmpfs so that the system will write out of the contents of
    the memory-based filesystem rather than reducing process working sets
    if the system encounters memory pressure. I'm not sure to what extent
    this is applicable to FreeBSD's md device.

    Also, will FreeBSD double-buffer md based devices if it does need to
    scribble their contents to disk, or is something like what Mach calls a
    "unified buffer cache" available? 

    -- 
-Chuck
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  • Next message: Arie J. Gerszt: "disk error / failure: need help! (smart failure predicted)"

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