Date: Mon, 2 Jul 2007 20:52:24 +0300 From: "Abdullah Ibn Hamad Al-Marri" <almarrie@gmail.com> To: "Jack Stone" <antennex@hotmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: kern.hz="100" stops high-pitched whine Message-ID: <499c70c0707021052p34e5197cjdfd8b956811b7fd6@mail.gmail.com> In-Reply-To: <BAY125-F3001869A4CBB8CAF4B378BCC0D0@phx.gbl> References: <4687B02B.7080106@mac.com> <BAY125-F3001869A4CBB8CAF4B378BCC0D0@phx.gbl>
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On 7/2/07, Jack Stone <antennex@hotmail.com> wrote: > >From: Chuck Swiger <cswiger@mac.com> > >To: cpghost <cpghost@cordula.ws> > >CC: questions <freebsd-questions@freebsd.org> > >Subject: Re: kern.hz="100" stops high-pitched whine > >Date: Sun, 01 Jul 2007 09:46:19 -0400 > > > >cpghost wrote: > >>Are there any reasons NOT changing kern.hz from the > >>default 1000 back to 100? With my typical mix of > >>desktop apps (EPIA) and networking / server (Soekris), > >>everything seems to be running just as smoothly with > >>100 Hz than with 1000 Hz (testing now for two weeks > >>without problems). Even playing videos with mplayer > >>on the EPIA doesn't look different in any way. > >> > >>Is it okay to stay with 100 Hz with this type of > >>low-speed CPU/boards? Or are there some compelling > >>reasons not to? > > > >Actually, many Unix systems ran with HZ=100 until a few years ago, about > >when Gb ethernet and CPUs became common. A slower machine like the EPIA > >boxes do quite well with HZ=100/200/250 or so...HZ=1000 is better if you > >have a fast box running lots of concurrent processes, and/or are proxying > >or routing network traffic where the difference between 10 ms and 1ms of > >latency adds up and/or effects other systems. > > > >-- > >-Chuck > > A while ago, I noticed someone's kernel config that included: > hertz=2000 > which made me wonder where this setting info comes from? > > I've been using hertz=1000 however, with my much faster boxes, is this > appropriate now? > > Thanks, > Jack I don't know if the info is correct up to now or not, but I use pf firewall, and I run IRC servers, I saw it in NOTES. ##################################################################### # NETWORKING OPTIONS # # DEVICE_POLLING adds support for mixed interrupt-polling handling # of network device drivers, which has significant benefits in terms # of robustness to overloads and responsivity, as well as permitting # accurate scheduling of the CPU time between kernel network processing # and other activities. The drawback is a moderate (up to 1/HZ seconds) # potential increase in response times. # It is strongly recommended to use HZ=1000 or 2000 with DEVICE_POLLING # to achieve smoother behaviour. # Additionally, you can enable/disable polling at runtime with help of # the ifconfig(8) utility, and select the CPU fraction reserved to # userland with the sysctl variable kern.polling.user_frac # (default 50, range 0..100). # # Not all device drivers support this mode of operation at the time of # this writing. See polling(4) for more details. options DEVICE_POLLING -- Maybe it's out of date now for 2000? -- Regards, -Abdullah Ibn Hamad Al-Marri Arab Portal http://www.WeArab.Net/
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