From owner-freebsd-current@FreeBSD.ORG Fri Mar 21 22:36:26 2008 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 423CB1065670 for ; Fri, 21 Mar 2008 22:36:26 +0000 (UTC) (envelope-from barney_cordoba@yahoo.com) Received: from web63911.mail.re1.yahoo.com (web63911.mail.re1.yahoo.com [69.147.97.126]) by mx1.freebsd.org (Postfix) with SMTP id BC2298FC15 for ; Fri, 21 Mar 2008 22:36:25 +0000 (UTC) (envelope-from barney_cordoba@yahoo.com) Received: (qmail 8207 invoked by uid 60001); 21 Mar 2008 22:36:24 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:Date:From:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding:Message-ID; b=b24EfCTpJ6BZCh75aVLCHk6leOG1Vm71vdSS/FbVLP7SCVO/k2jbzkijB0BRrN0GKZD6BrwZMtwGENiZqwjpfLaSDExfaRPlZpWWRGZnCuCEpC/jtj0rXfi2HAbvPFeRDHme7fIA9sSYKK8FQBlgsDkadoyzX2gArRKXnvsoo+Y=; X-YMail-OSG: SSb__NYVM1k1i4VrjLTbUbh4yE9IGc1EWNeegSgiW_N1SNtEOiIxL3mSAzUUJGmiaBC_Mh_IZ_qY62_tCF8.daZF37.gAQupUd9b2gjbzMvEJkuK.xGe0h7iqnoeGDx46fjfdDOp.L90e98- Received: from [24.45.195.185] by web63911.mail.re1.yahoo.com via HTTP; Fri, 21 Mar 2008 15:36:24 PDT Date: Fri, 21 Mar 2008 15:36:24 -0700 (PDT) From: Barney Cordoba To: Julian Elischer In-Reply-To: <47E40196.6060703@elischer.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Message-ID: <817070.5892.qm@web63911.mail.re1.yahoo.com> Cc: current@freebsd.org Subject: Re: kvm_read() vs ioctl performance X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 21 Mar 2008 22:36:26 -0000 --- Julian Elischer wrote: > Barney Cordoba wrote: > > I have an app which reads stats from the kernel > > periodically, and there can be a lot of > iterations, > > sometimes 20,000 or more. I'm thinking of > converting > > from an ioctl method to kvm_read(). KVM is > certainly > > simpler, but its not clear what overhead is > involved, > > since kvm_read() likely has to call the kernel > also. > > > > Does anyone have a handle on the difference in > > overhead, assuming that the ioctl call is to a > module > > which does nothing more than copy the data and > return? > > tried a shared memory page? No, but I built a test and kvm_read is 70 times faster, in case anyone is interested. Barney ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs