From owner-freebsd-stable@FreeBSD.ORG Thu Oct 9 17:07:31 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 37E22106568F for ; Thu, 9 Oct 2008 17:07:31 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from QMTA10.westchester.pa.mail.comcast.net (qmta10.westchester.pa.mail.comcast.net [76.96.62.17]) by mx1.freebsd.org (Postfix) with ESMTP id 105498FC1C for ; Thu, 9 Oct 2008 17:07:29 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from OMTA02.westchester.pa.mail.comcast.net ([76.96.62.19]) by QMTA10.westchester.pa.mail.comcast.net with comcast id QciR1a0010QuhwU5Ah7VY0; Thu, 09 Oct 2008 17:07:29 +0000 Received: from koitsu.dyndns.org ([69.181.141.110]) by OMTA02.westchester.pa.mail.comcast.net with comcast id Qh7T1a0052P6wsM3Nh7TrH; Thu, 09 Oct 2008 17:07:29 +0000 X-Authority-Analysis: v=1.0 c=1 a=2tN0PPoFp_AA:10 a=QycZ5dHgAAAA:8 a=15VyqwAHxlPrdw5ZANkA:9 a=wWbSklcSKAZwjB6KymyaXekqaqUA:4 a=EoioJ0NPDVgA:10 a=LY0hPdMaydYA:10 Received: by icarus.home.lan (Postfix, from userid 1000) id 11E24C9419; Thu, 9 Oct 2008 10:07:27 -0700 (PDT) Date: Thu, 9 Oct 2008 10:07:27 -0700 From: Jeremy Chadwick To: Ian Smith Message-ID: <20081009170727.GA9542@icarus.home.lan> References: <20081008183652.GA83351@icarus.home.lan> <501797.33750.qm@web39105.mail.mud.yahoo.com> <20081009051214.GA94941@icarus.home.lan> <20081010023938.R16723@sola.nimnet.asn.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081010023938.R16723@sola.nimnet.asn.au> User-Agent: Mutt/1.5.18 (2008-05-17) Cc: bf , freebsd-stable@freebsd.org Subject: Re: Recent Problems with RELENG_7 i386 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 09 Oct 2008 17:07:31 -0000 On Fri, Oct 10, 2008 at 03:51:02AM +1100, Ian Smith wrote: > I see bf has since posted these values, but I'd already clipped stuff > from the original post with kernel config and verbose dmesg, already > wondering why the two didn't match, like: > > | options HZ=1000 > | options DEVICE_POLLING > > but > > | CPU: AMD Athlon(tm) Processor (906.35-MHz 686-class CPU) > | Timecounter "ACPI-safe" frequency 3579545 Hz quality 850 > | inittimecounter(0)... Timecounters tick every 10.000 msec > > ie HZ=100, as mentioned, and using ACPI-safe as later confirmed. So > it's either a different kernel or bf updated kern.hz from loader.conf? Yep -- his original mail had loader.conf shown, with this in it (near the bottom): kern.hz=100 > > Well, I believe HZ was increased from 100 to 1000 long ago (RELENG_6?) > > as a default. I'm really not sure of the implications of decreasing it, > > besides having less granularity for some things (the only things I know > > of would be something pertaining to firewalls, I just can't remember > > what. My brain is full. :-) ) > > You need a day off :) But yes, RELENG_5 still had HZ=100 default, long > after the 'average' CPU clock frequency was 10 or more times faster than > the 166MHz Pentiums and such (mostly then on only 100Mbps ethernet) that > were comfortable at 100Hz slicing. 1000Hz was a big shift to catch up. > > In a day or so playing around with it years ago, I found 200-250Hz good > for 300MHz, 500Hz a bit much, 1000Hz way too busy, and find my 1133MHz > P3-M happy enough at 1000Hz, though I've done no specific tests on it. > > Some people had perhaps similar clock issues when their fast processors > were throttling/stepping down to very low speeds (100, even 75MHz) while > still slicing at 1000Hz, which I didn't find too surprising. Limiting > minimum CPU freq to 300Mz or more seemed to solve many such issues, but > I haven't your perseverance for digging up the relevant threads .. > > Even in 5.5-S (/sys/conf/NOTES and /sys/i386/conf/NOTES) HZ=1000 or 2000 > was suggested for DEVICE_POLLING (which bf included in config, though > maybe it's not enabled?) and HZ=1000 or more was recommended when using > DUMMYNET with ipfw - to provide smoother queue dispatching, I gather. > > Bottom line, IMHO, bf should probably run the default 1000Hz, 500 at > least, on an Athlon 900. With powerd, maybe set min. freq >= 150MHz? Wow, this is fantastic information. You've just educated me a great bit about the history and use of HZ. I've always had a "general" idea of its importance and key role, but I was never fully aware of the history. P.S. -- I need more like 6 months off. I've never taken an official (read: real) vacation my entire life. Maybe some day I'll get to travel to Seoul and visit Pyun Yong-Hyeon and drink lots of soju. :-) -- | Jeremy Chadwick jdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB |