my latest scheduler patches include support for SCHED_BATCH, which is
a replacement for SCHED_IDLE - a new way to run lowprio, CPU-intensive,
non-interactive processes, without affecting any other process in the
system. SCHED_BATCH processes utilize 'CPU idle time', without taking
away CPU time from any other process.

- for 2.4, it's in the sched-2.4.19-pre10-ac2-B3 patch and upwards.
- for 2.5, it's in the sched-2.5.24-D3 patch and upwards.

the setbatch.c utility enables you to set an existing process to
idle priority. Eg. to change a shell's scheduling policy to SCHED_BATCH:

	./setbatch $$

all subsequently started commands will run under SCHED_BATCH priority.