From owner-freebsd-arch@FreeBSD.ORG Tue May 31 01:40:00 2005 Return-Path: X-Original-To: freebsd-arch@FreeBSD.org Delivered-To: freebsd-arch@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 0FCBF16A41C; Tue, 31 May 2005 01:40:00 +0000 (GMT) (envelope-from bde@zeta.org.au) Received: from mailout1.pacific.net.au (mailout1.pacific.net.au [61.8.0.84]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8BF3D43D49; Tue, 31 May 2005 01:39:59 +0000 (GMT) (envelope-from bde@zeta.org.au) Received: from mailproxy2.pacific.net.au (mailproxy2.pacific.net.au [61.8.0.87]) by mailout1.pacific.net.au (8.12.3/8.12.3/Debian-7.1) with ESMTP id j4V1dnrI008810; Tue, 31 May 2005 11:39:49 +1000 Received: from katana.zip.com.au (katana.zip.com.au [61.8.7.246]) by mailproxy2.pacific.net.au (8.12.3/8.12.3/Debian-7.1) with ESMTP id j4V1djMC020885; Tue, 31 May 2005 11:39:46 +1000 Date: Tue, 31 May 2005 11:39:47 +1000 (EST) From: Bruce Evans X-X-Sender: bde@delplex.bde.org To: Robert Watson In-Reply-To: <20050530182650.R90885@fledge.watson.org> Message-ID: <20050531113008.R91505@delplex.bde.org> References: <4298E316.9020303@samsco.org> <20050529121224.L52379@fledge.watson.org> <20050530.102803.74664036.imp@bsdimp.com> <20050530182650.R90885@fledge.watson.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: daniel_k_eriksson@telia.com, freebsd-arch@FreeBSD.org Subject: Re: MPSAFE CAM? X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 31 May 2005 01:40:00 -0000 On Mon, 30 May 2005, Robert Watson wrote: > On Mon, 30 May 2005, M. Warner Losh wrote: > >> In message: <20050529121224.L52379@fledge.watson.org> >> Robert Watson writes: >> : driver, we've gained many of the benefits of making MPSAFE. Especially >> if >> : we can knock Giant off a lot of the remaining non-CAM device drivers that >> : it's still stuck over. >> >> usb, psm and atkbd are important ones for interactive performance... > > And the tty subsystem becomes an immediate dependency for several of these. Interactive performance is irrelevant here. You can can lose efficiency by competing for Giant a few hundred thousand times in the time that it takes an interactive user to notice. The problem is that non-interactive performance is impaired by using Giant locking anywhere. Using it for interactive devices is only a problem if the interaction often requires holding Giant for a long time. It doesn't for most input devices including keyboards, but it might for slow bulk output devices like syscons consoles. Bruce