From owner-freebsd-hackers Fri Feb 1 0:21:36 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from iguana.icir.org (iguana.icir.org [192.150.187.36]) by hub.freebsd.org (Postfix) with ESMTP id BC1F137B493 for ; Fri, 1 Feb 2002 00:21:09 -0800 (PST) Received: (from rizzo@localhost) by iguana.icir.org (8.11.3/8.11.3) id g118KHi48559; Fri, 1 Feb 2002 00:20:17 -0800 (PST) (envelope-from rizzo) Date: Fri, 1 Feb 2002 00:20:17 -0800 From: Luigi Rizzo To: Mike Silbersack Cc: Storms of Perfection , thierry@herbelot.com, replicator@ngs.ru, hackers@FreeBSD.org Subject: Re: Clock Granularity (kernel option HZ) Message-ID: <20020201002017.B48439@iguana.icir.org> References: <3197.208.141.46.249.1012516570.squirrel@test.outloud.org> <20020131172729.X38382-100000@patrocles.silby.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020131172729.X38382-100000@patrocles.silby.com> User-Agent: Mutt/1.3.23i Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Thu, Jan 31, 2002 at 05:33:28PM +0000, Mike Silbersack wrote: > > On Thu, 31 Jan 2002, Storms of Perfection wrote: > > > I'm going to benchmark different network senarious with different options > > to see what I can get, and what works best. If someone wants to help me > > out, I could maybe write up a article about it? > > I don't think you'll end up seeing the performance improvements you're > looking for. The case where HZ=1000 is really useful is when using > dummynet; the more accurate scheduling is necessary for it to handle high > data rate pipes properly. HZ also has an impact on select() behaviour when timeouts are used (and device drivers using timeouts as well). A lot of software uses select() with a very short timeout which is usually rounded up to the next tick. If the author of the software is unaware of what goes on (likely) there might be negative effects on performance because such programs stay idle longer than they should. cheers luigi To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message