syncer_maxdelay patch (PR#21859)

[Chatchawan Wongsiriprasert]

Hi,
   I try to make my notebook use less energy by increasing kern.filedelay,
kern.dirdelay and kern.metadelay and found that I can not increase these
values greater than the syncer_maxdelay value that hard code to 32 seconds
in FreeBSD 4.8 (you can set, it show ,but, ignored).

   After I search the Internet , I found that there is old FreeBSD PR
(PR#21859 --  http://www.freebsd.org/cgi/query-pr.cgi?pr=PR%2321859) that
propose to make syncer_maxdelay a kernel option and allow root to set
kern.syncdelay that also limit maximum value of the previous 3 variables.

   The patch seem to be ignored ( the post date is  Mon Oct 09 05:20:01
PDT 2000 ) , so never make it way to FreeBSD kernel.

   My question is

   1. Why this patch is ignored? Is it too dangerous or it is useless?
   2. Is there any adition ways to reduce the power need by the notebook
in addition to:
      (1) reduce CPU speed
      (2) dim the backlight
      (3) Change system cron to delay the activation of some frequency run
jobs such as atrun

Regards,
Chatchawan Wongsiriprasert