From owner-freebsd-scsi Thu Jan 30 18:22:05 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id SAA22332 for freebsd-scsi-outgoing; Thu, 30 Jan 1997 18:22:05 -0800 (PST) Received: from dyson.iquest.net (dyson.iquest.net [198.70.144.127]) by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id SAA22324 for ; Thu, 30 Jan 1997 18:22:01 -0800 (PST) Received: (from root@localhost) by dyson.iquest.net (8.8.4/8.6.9) id VAA06077; Thu, 30 Jan 1997 21:21:50 -0500 (EST) From: "John S. Dyson" Message-Id: <199701310221.VAA06077@dyson.iquest.net> Subject: Re: XXXminpys question To: joerg_wunsch@uriah.heep.sax.de Date: Thu, 30 Jan 1997 21:21:50 -0500 (EST) Cc: freebsd-scsi@freebsd.org In-Reply-To: from "J Wunsch" at Jan 30, 97 10:56:20 pm Reply-To: dyson@freebsd.org X-Mailer: ELM [version 2.4 PL24 ME8] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-scsi@freebsd.org X-Loop: FreeBSD.org Precedence: bulk > As Peter Dufault wrote: > > > > The adapters _are_ the reason for a minphys, so there should only be > > > one at all. We should probably add it to the cdevsw entries. It can > > > default to minphys (64 KB). > > > > You still want an overall system minphys to prevent a rogue driver / rogue > > dd from crashing the system. It is the maximum amount you're willing to > > guarantee to lock down for a raw transfer. > > I remember that David Greenman once said that the main reason for the > existing minphys was the limitation of the SCSI adapters. > > Maybe there should be another minphys, but more something like 1 MB or > larger then. The existing 64 KB limitation is something seriously > small. > It will require some restructuring of the pbuf (physical I/O buffer) code, but isn't that bad to do. It has been in my queue for a while. If the driver-savvy people can work out a way to query the driver for the maximum I/O size, I can/will implement the upper level changes. John Dyson