> > i think that the change is broken and should be backed out at least.
> 
> The change is what made a machine doing big builds in the background
> still useful for long-running interactive processes with marginal cpu
> usage. Leave it in.
> 
> (Without the change, a process could intentionally fork thousands of 
> workers to consume half a timeslice each, and none of them would ever
> be penalized for it).

do you mean that the following is an intended behaviour?
to me, it seems quite broken.  it actually makes interactive shell
unusable.

YAMAMOTO Takashi

bear% for x in $(jot 10);do ps -Ocpu -p$$;done
  PID CPU TT STAT    TIME COMMAND
17301   0 p0 Ss   0:00.16 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301   1 p0 Ss   0:00.16 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301   2 p0 Ss   0:00.16 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301   4 p0 Ss   0:00.16 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301   8 p0 Ss   0:00.16 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301  16 p0 Ss   0:00.16 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301  33 p0 Ss   0:00.16 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301  36 p0 Ss   0:00.17 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301  36 p0 Ss   0:00.17 /usr/pkg/bin/zsh 
  PID CPU TT STAT    TIME COMMAND
17301  36 p0 Ss   0:00.17 /usr/pkg/bin/zsh