The attached patch increases HZ to 800 for kernels compiled for 686
It tries to hide the HZ change from userspace. The places I found were:

o /proc/stat
o /proc/<pid>/stat
o /proc/<pid>/cpu
o BSD Process Accounting
o siginfo
o sys_times

Not handled:
o the ip routing sysctls [defined in jiffies...:( ]

also note there are drivers that assume HZ==100 (initio scsi for one).


The numbers I've got so far doesn't look very good however,
a 3% drop in performance (HZ=1024) is a bit much.


[I did this patch from scratch so that the chance of spotting all
 places requiring updates would be greater. turned up to be a good
 thing - it handles a few more cases than the previously mentioned
 patch by Kurt Garloff]

What did I miss? :)