Re: Indexers comparison

[Joe Shaw <joeshaw novell com>]

Hi again,

On Thu, 2007-01-18 at 14:20 -0500, Joe Shaw wrote:
> > choosing another scheduling policy (like sched_batch) is a
> > bit better, as a sched_batch process will use 0% cpu in presence of
> > another process trying to get 100% cpu.
> 
> I looked into this today, and this isn't how the SCHED_BATCH policy
> works on Linux (at least with 2.6.20).  Indeed doing so would cause an
> issue with priority inversion, since a blocked process could hold some
> resource while another process spun.
> 
> SCHED_BATCH simply drops the sleep interval calculation, which
> determines the bonus (between -5 and +5) on top of your nice value, and
> automatically gives your process a -5 bonus.

Oops, sorry, typo.  I meant it would automatically get a +5 bonus.  So,
to recap... :) Something run with SCHED_BATCH at nice 0 would act as
though it were run at +5.  With SCHED_OTHER it would be anywhere from -5
to +5 depending on interactivity.

SCHED_BATCH is a bad name considering the older (inversion-prone)
implementation.  A better name would be SCHED_FIXED.

Joe