user:sys time ratio

Robert Watson rwatson at
Sun Nov 30 08:09:18 PST 2003

On Sun, 30 Nov 2003, Colin Percival wrote:

>    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. 

It sounds like you have multiple logical cores -- have you tried building
a kernel without SMP support to see what happens?

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at      Senior Research Scientist, McAfee Research

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