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From: Bruce Evans <bde@zeta.org.au>
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On Fri, 28 Mar 2003, Dag-Erling [iso-8859-1] Sm=F8rgrav wrote:

> Bruce Evans <bde@zeta.org.au> writes:
> > Instead of fixing the comparison and any other logic bugs, I rewrote th=
e
> > function using orl instead of scasl, and simpler logic (ignore the chan=
ges
> > for the previous function in the same hunk).
>
> Could you please commit this?  Nothing uses it, so it won't break
> anything, but it'll make testing and benchmarking easier for
> interested parties.

Er, it is used (in pmap.c).

I recently learned that makeworld is an interesting benchmark for zeroing
pages (all %times on a system with 1 Athlon and 1GB of memory):
- makeworld spends at least 3-5% of its time zeroing pages
- turning off vm.idlezero_enable increases makeworld time by 1-2%
  and moves the place where the zeroing is done significantly.  With
  vm.idlezero_enable off, most of the idle zeroing is done in process
  context and gets charged to makeworld; otherwise it is done in the
  pagezero task and gets charged to that.  Most but not all of the time
  spent in the pagezero task is "free", and we lose the 1-2% by
  doing all zeroing in process context.
- SCHED_ULE breaks scheduling of idleprio processes.  This results in
  pagezero being too active.  It costs 1-2% instead of saving 1-2%.

Bruce