From owner-freebsd-hackers@FreeBSD.ORG Mon Apr 21 11:33:24 2003 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6633937B401 for ; Mon, 21 Apr 2003 11:33:24 -0700 (PDT) Received: from ns1.xcllnt.net (209-128-86-226.BAYAREA.NET [209.128.86.226]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7584343FE1 for ; Mon, 21 Apr 2003 11:33:23 -0700 (PDT) (envelope-from marcel@xcllnt.net) Received: from dhcp01.pn.xcllnt.net (dhcp01.pn.xcllnt.net [192.168.4.201]) by ns1.xcllnt.net (8.12.9/8.12.9) with ESMTP id h3LIXNwk092792; Mon, 21 Apr 2003 11:33:23 -0700 (PDT) (envelope-from marcel@piii.pn.xcllnt.net) Received: from dhcp01.pn.xcllnt.net (localhost [127.0.0.1]) by dhcp01.pn.xcllnt.net (8.12.9/8.12.9) with ESMTP id h3LIXMT0000738; Mon, 21 Apr 2003 11:33:22 -0700 (PDT) (envelope-from marcel@dhcp01.pn.xcllnt.net) Received: (from marcel@localhost) by dhcp01.pn.xcllnt.net (8.12.9/8.12.9/Submit) id h3LIXMpm000737; Mon, 21 Apr 2003 11:33:22 -0700 (PDT) Date: Mon, 21 Apr 2003 11:33:22 -0700 From: Marcel Moolenaar To: Jake Burkholder Message-ID: <20030421183322.GA557@dhcp01.pn.xcllnt.net> References: <20030421055332.GA4680@dhcp01.pn.xcllnt.net> <20030421132449.GA50754@locore.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20030421132449.GA50754@locore.ca> User-Agent: Mutt/1.5.3i cc: freebsd-hackers@freebsd.org Subject: Re: Is pmap_kextract() allowed to fault? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 21 Apr 2003 18:33:24 -0000 On Mon, Apr 21, 2003 at 09:24:49AM -0400, Jake Burkholder wrote: > Apparently, On Sun, Apr 20, 2003 at 10:53:32PM -0700, > Marcel Moolenaar said words to the effect of; > > > Gang, > > > > On ia64 pmap_kextract() uses the tpa instruction which given a > > virtual address returns the physical address based on the > > translation registers and cache (ie TLB). This can fault when > > there's currently no mapping for the virtual address. > > > > Since all other architectures have a non-faulting implementation > > (AFAICT), I'm a bit worried that we might get into trouble on > > ia64. I couldn't find anything about pmap_kextract(), so maybe > > anybody can enlighten me: > > > > 1. Is pmap_kextract() allowed to fault? > > It depends what kind of fault. Will tpa fail if it causes a tlb fault > and the page is not in the vhpt (or whatever the fault handler searches), > or will it end up calling vm_fault and actually trying to fault in the > page? It will end up calling vm_fault() if so required. > > 2. Is pmap_kextract() used often enough that using the cpu's TLB > > is a possible performance speedup even if there are costly faults > > that can sometimes happen? > > I doubt it. Ok, thanks. I think I'll use a non-trapping implementation then. There's just too much circumstantiality... -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net