From owner-freebsd-questions@FreeBSD.ORG Fri Nov 25 00:21:52 2005 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 632B916A42C for ; Fri, 25 Nov 2005 00:21:52 +0000 (GMT) (envelope-from kris@obsecurity.org) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4632B43D78 for ; Fri, 25 Nov 2005 00:21:31 +0000 (GMT) (envelope-from kris@obsecurity.org) Received: from obsecurity.dyndns.org (elvis.mu.org [192.203.228.196]) by elvis.mu.org (Postfix) with ESMTP id 09BB01A3C1A; Thu, 24 Nov 2005 16:21:28 -0800 (PST) Received: by obsecurity.dyndns.org (Postfix, from userid 1000) id 5E9C051593; Thu, 24 Nov 2005 19:21:27 -0500 (EST) Date: Thu, 24 Nov 2005 19:21:27 -0500 From: Kris Kennaway To: Wojciech Puchar Message-ID: <20051125002127.GB32821@xor.obsecurity.org> References: <20051124013438.T8326@chylonia.3miasto.net> <20051124204359.GD30073@xor.obsecurity.org> <20051125010708.B86615@chylonia.3miasto.net> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="oC1+HKm2/end4ao3" Content-Disposition: inline In-Reply-To: <20051125010708.B86615@chylonia.3miasto.net> User-Agent: Mutt/1.4.2.1i Cc: freebsd-questions@freebsd.org, Markus Trippelsdorf , Kris Kennaway Subject: Re: so much clock interrupts?! X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Nov 2005 00:21:52 -0000 --oC1+HKm2/end4ao3 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Nov 25, 2005 at 01:08:42AM +0100, Wojciech Puchar wrote: > >>That's why I have kern.hz=3D"100" in my /boot/loader.conf . > > > >Have you been able to measure a performance benefit from reducing it? > >Have you shown that reducing it does not cause your performance to > >*drop*? It was increased for a reason..it actually increases > >performance on some workloads. > > > no i'm just asking. >=20 > does hz=3D1000 means that if i run >1 CPU-bound process per processor it'= s=20 > switched 1000 times per second between them? or just 1000 times per secon= d=20 > system call is issued that does many system duties, but switches processe= s=20 > with different frequency? It's used to drive timers and periodic events, including scheduling. Keep in mind that modern computers are roughly 10 times faster than they were a few years ago. Something that runs every 1/100 of a second is actually waiting for 10 times as many CPU cycles as it was on the older machine, which means that it may be working proportionally less efficiently on the new machine. Kris --oC1+HKm2/end4ao3 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (FreeBSD) iD8DBQFDhlkHWry0BWjoQKURAkznAJ0SBXxfl/ghgBF2PiiuKj1ucyPSDwCfUNAz F1zdGgngNbS9L8qtCpsoDX8= =aBr6 -----END PGP SIGNATURE----- --oC1+HKm2/end4ao3--