From owner-freebsd-hackers Thu Jun 3 14:36:42 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (Postfix) with ESMTP id 5E9F9158C6 for ; Thu, 3 Jun 1999 14:36:41 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id OAA00394; Thu, 3 Jun 1999 14:36:38 -0700 (PDT) (envelope-from dillon) Date: Thu, 3 Jun 1999 14:36:38 -0700 (PDT) From: Matthew Dillon Message-Id: <199906032136.OAA00394@apollo.backplane.com> To: Jos Backus Cc: Wilko Bulte , zzhang@cs.binghamton.edu, freebsd-hackers@FreeBSD.ORG Subject: Re: The choice of MAXPHYS References: <19990603172907.A20792@hal.mpn.cp.philips.com> <199906031730.TAA00686@yedi.iaf.nl> <19990603231216.A36464@hal.mpn.cp.philips.com> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :On Thu, Jun 03, 1999 at 07:30:20PM +0200, Wilko Bulte wrote: :> 20 bits. But older cards can do no more than 64 kB. : :Indeed, 20 bits (=1 Mbyte) for the address, 16 bits for the transfer counter :(offset). : :-- :Jos Backus _/ _/_/_/ "Reliability means never MAXPHYS is ultimately a limitation on the size of the b_pages array in the struct buf structure. The default is 128 KBytes. Device Drivers are supposed to break up I/O's into manageable sections themselves. Maybe when the buffer I/O / VFS subsystem is rewritten later this year we can get rid of the artificial limitations. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message