From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 09 Jan 2006 08:56:43 +0000 (GMT) Received: from 209-232-97-206.ded.pacbell.net ([209.232.97.206]:23021 "EHLO dns0.mips.com") by ftp.linux-mips.org with ESMTP id S8133706AbWAII4X (ORCPT ); Mon, 9 Jan 2006 08:56:23 +0000 Received: from mercury.mips.com (sbcns-dmz [209.232.97.193]) by dns0.mips.com (8.12.11/8.12.11) with ESMTP id k098wuDR010905; Mon, 9 Jan 2006 00:58:57 -0800 (PST) Received: from grendel (grendel [192.168.236.16]) by mercury.mips.com (8.12.9/8.12.11) with SMTP id k098wtYr002864; Mon, 9 Jan 2006 00:58:56 -0800 (PST) Message-ID: <005a01c614fb$2fe76b00$10eca8c0@grendel> From: "Kevin D. Kissell" To: "Sathesh Babu Edara" , , References: <200601090742.k097gYaZ017304@lilac.hdcindia.analog.com> Subject: Re: Date: Mon, 9 Jan 2006 10:00:48 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1506 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1506 X-Scanned-By: MIMEDefang 2.39 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 9810 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: kevink@mips.com Precedence: bulk X-list: linux-mips There is no "ideal" value for a given processor frequency. The lower the value, the less interrupt processing overhead, but the slower the response time to events that are detected or serviced during clock interrupts. 1000 HZ *may* be a sensible value (I have my doubts, personally) for 2+ GHz PC processors, but it's excessive (IMHO) for a 200MHz processor and unworkable for a 20MHz CPU. I think that 100HZ is still a reasonable value for an embedded RISC CPU, but the "ideal" value is going to be a function of the application. Regards, Kevin K. ----- Original Message ----- From: "Sathesh Babu Edara" To: "'Kevin D. Kissell'" ; ; Sent: Monday, January 09, 2006 8:43 AM Subject: RE: > > Hi, > Appreciate your response . > > What is the ideal HZ value if the processor speed is 200Mhz?. > > Regards, > Sathesh > -----Original Message----- > From: Kevin D. Kissell [mailto:kevink@mips.com] > Sent: Wednesday, January 04, 2006 6:37 PM > To: Sathesh Babu Edara > Cc: linux-mips-bounce@linux-mips.org; linux-mips@linux-mips.org > Subject: Re: > > Sathesh Babu Edara wrote: > > > > > > Hi, > > 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. > > Regards, > > Kevin K. > > > From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from 209-232-97-206.ded.pacbell.net ([209.232.97.206]:23021 "EHLO dns0.mips.com") by ftp.linux-mips.org with ESMTP id S8133706AbWAII4X (ORCPT ); Mon, 9 Jan 2006 08:56:23 +0000 Message-ID: <005a01c614fb$2fe76b00$10eca8c0@grendel> From: "Kevin D. Kissell" References: <200601090742.k097gYaZ017304@lilac.hdcindia.analog.com> Subject: Re: Date: Mon, 9 Jan 2006 10:00:48 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-Path: Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org To: Sathesh Babu Edara , linux-mips-bounce@linux-mips.org, linux-mips@linux-mips.org Message-ID: <20060109090048.d5ijo6d8uDsZIHVxSod3RqkzccwUrt_AWA-G2VnyROM@z> There is no "ideal" value for a given processor frequency. The lower the value, the less interrupt processing overhead, but the slower the response time to events that are detected or serviced during clock interrupts. 1000 HZ *may* be a sensible value (I have my doubts, personally) for 2+ GHz PC processors, but it's excessive (IMHO) for a 200MHz processor and unworkable for a 20MHz CPU. I think that 100HZ is still a reasonable value for an embedded RISC CPU, but the "ideal" value is going to be a function of the application. Regards, Kevin K. ----- Original Message ----- From: "Sathesh Babu Edara" To: "'Kevin D. Kissell'" ; ; Sent: Monday, January 09, 2006 8:43 AM Subject: RE: > > Hi, > Appreciate your response . > > What is the ideal HZ value if the processor speed is 200Mhz?. > > Regards, > Sathesh > -----Original Message----- > From: Kevin D. Kissell [mailto:kevink@mips.com] > Sent: Wednesday, January 04, 2006 6:37 PM > To: Sathesh Babu Edara > Cc: linux-mips-bounce@linux-mips.org; linux-mips@linux-mips.org > Subject: Re: > > Sathesh Babu Edara wrote: > > > > > > Hi, > > 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. > > Regards, > > Kevin K. > > >