Re: /dev/shm

From: Matthias Andree (matthias.andree_at_gmx.de)
Date: 07/07/03

  • Next message: Marcin Dalecki: "Re: /dev/shm" 
    Date: Mon, 7 Jul 2003 15:54:59 +0200
To: current@freebsd.org

    On Mon, 07 Jul 2003, Marcin Dalecki wrote:

    > The point is that this is one of the reasons why the top command in
    > question takes a lot of relative CPU time under Linux. Some
    > "faster" versions of procps utils try to cache data but the trade off
    > is simply the fact that the results are not 100% accurate.

    Top data is not accurate (I though that was obvious ;-).

    It's an obsolete snapshot the very moment it's printed to your console,
    and I bet it changes as you read with a lot of implementations because
    no-one wants to beat the big kernel lock on the process list just
    because some user happens to run top, might be a nice DoS otherwise,
    fork-bombing top...

    If you want accurate data, use a kernel debugger with remote interface
    and make sure the machine does nothing except servicing the debugger
    interface.

    > I tought this was obvious?

    Why do I care? 0.58user 0.89system 1:00.91elapsed 2%CPU -- on a 266 MHz
    Pentium-II, Linux 2.4, 5 years old, with 190 processes. The box idles
    73% of the time it's up, there's _ample_ CPU power left. 

    -- 
Matthias Andree
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  • Next message: Marcin Dalecki: "Re: /dev/shm"