Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!ll-xn!adelie!munsell!jwf From: jwf@munsell.UUCP (Jim Franklin) Newsgroups: comp.unix.wizards Subject: BSD 4.2 minphys() < 64K Message-ID: <376@wyszecki.munsell.UUCP> Date: Fri, 12-Dec-86 12:00:43 EST Article-I.D.: wyszecki.376 Posted: Fri Dec 12 12:00:43 1986 Date-Received: Mon, 15-Dec-86 19:39:08 EST Organization: Eikonix Corp., Bedford, MA Lines: 19 Why does minphys() in BSD 4.2 systems still limit block i/o transfers to 63 * 1024 bytes? I assume that this is an ancient artifact from PDP-11 days, when int's were 16 bits and 64K bytes was considered a lot of memory. But processor memory is very cheap now, so we can afford to allocate much larger buffer pools. Block devices such as disks are also much faster and have higher densities. For example, 64K bytes is only 2 tracks on a Fujitsu 2361. I would like to be able to blast a 1/4 megabyte to a disk in one i/o -- the disk, disk controller, and device driver can all deal with this. But minphys() is the bottleneck. Does anyone know why minphys is still < 64 K? Has anyone successfully increased this, or know why it can't be done? Thanks ... ----- {harvard!adelie,{decvax,allegra,talcott}!encore}!munsell!jwf Jim Franklin, Eikonix Corp., 23 Crosby Drive, Bedford, MA 01730 Phone: (617) 275-5070 x415