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To: Sathesh Babu Edara <>
Subject: Re:
From: "Kevin D. Kissell" <>
Date: Wed, 04 Jan 2006 14:06:36 +0100
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Sathesh Babu Edara wrote:
   We have ported linux-2.6.12 kernel onto MIPS processor (LX4189) and the
processor speed is 200Mhz.
By default Linux-2.6.12 kernel comes with HZ value 1000.Will this HZ value
cause an overhead on the 200MHZ CPU.Can someone advise me on whether going
back to HZ vaule of 100 like Linux-2.4 will reduce the overhead on this
CPU.What are the side effects this change can cause?.

The 1000Hz clock should not actually cause any problems with a 200MHz
CPU, but it will suck up an annoyingly high percentage of available
cycles. Backing off to 100Hz may cause some degradation of some
real-time/interactive response times, but the improved overall
performance will probably more than make up for it.  I never build
with a HZ value greater than 100 these days, but then again, I'm
mostly running on FPGAs and other hardware emulators where the CPU
clock frequencies may be less than 1MHz, and are never more than 33MHz.
Note that a HZ  value of less than 100 may cause some kernel macros
to generate divide-by-zero operations/exceptions.


                Kevin K.

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