Date: Thu, 31 Jan 2002 23:13:44 +0100 From: Thierry Herbelot <thierry@herbelot.com> To: Eugene Panchenko <replicator@ngs.ru> Cc: hackers@FreeBSD.ORG Subject: Re: Clock Granularity (kernel option HZ) Message-ID: <3C59C198.78EDFEA9@herbelot.com> References: <web-8711515@intranet.ru>
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I've used a large collection of PCs running somewhat real-time network analysis with a HZ set at 5000Hz with absolutely no ill effects (this was with P-III-450's) using HZ=10000 was outside of the possibilities of the machines. one big gain is with timing, which will be better (I myself used NTP to have a coherent timing on the collection of PC's, with an inter-correlation better than 1 ms) TfH Eugene Panchenko wrote: > > Hello! > > I've seen various postings on the Net where people reported > network-related and overall performance improvements caused > by settig HZ kernel option to 1000 (for example), that is, > reducing a tick size to 1ms for their FreeBSD and Linux > systems. However, several problems seem to arise, such as > some device drivers do not include HZ in calculating their > timeout value, but simply assume HZ to be 100, and also some > utility programs such as top or ps take timing information > from the kernel in ticks, also assuming 10ms ticks, however, > most of these saying were related to Linux. How safe it is > to bump up HZ to, say, 1000 in FreeBSD (I use 4.5-STABLE)? > What pitfals will I encounter (drivers, top/ps)? Is there > are going to be [promised] performance increase? Do I > really need it? Thank you. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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