user:sys time ratio

From: Colin Percival (colin.percival_at_wadham.ox.ac.uk)
Date: 11/30/03

  • Next message: Poul-Henning Kamp: "Re: user:sys time ratio" 
    Date: Sun, 30 Nov 2003 14:20:52 +0000
To: freebsd-current@freebsd.org

       I've got a system running 5.2-BETA from 27/11/03, with the malloc_abort,
    malloc_junk, DEBUG=-g, DDB, INVARIANT*, and WITNESS* debugging options
    changed (as was done in 5.1-RELEASE).
       When running `make buildworld`, I see large amounts of sys time; eg, 27
    minutes user & 14 minutes sys for building 5.2, or 14 minutes user & 10
    minutes sys for building 4.9. I expected the ratio of user:sys to be much
    larger than this, and mailing list traffic indicates that a 4:1 ratio is
    typical. (FWIW, prior to changing the debugging options, the user:sys time
    ratio was around 1:1.)
       Can anyone suggest why the kernel seems to be behaving so sluggishly?

       The system hardware is P4 2.8Ghz, 865G, 2GB DDR, IDE drives; there is
    very little disk activity, so I'm sure that isn't the issue; and disabling
    HTT results in about a 2% improvement in both user and sys times.

    Colin Percival

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