From owner-cvs-all Mon Aug 17 20:54:43 1998 Return-Path: Received: (from daemon@localhost) by hub.freebsd.org (8.8.8/8.8.8) id UAA24421 for cvs-all-outgoing; Mon, 17 Aug 1998 20:54:43 -0700 (PDT) (envelope-from owner-cvs-all) Received: from freefall.freebsd.org (freefall.FreeBSD.ORG [204.216.27.21]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id UAA24414; Mon, 17 Aug 1998 20:54:42 -0700 (PDT) (envelope-from bde@FreeBSD.org) From: Bruce Evans Received: (from bde@localhost) by freefall.freebsd.org (8.8.8/8.8.5) id UAA24421; Mon, 17 Aug 1998 20:54:39 -0700 (PDT) Date: Mon, 17 Aug 1998 20:54:39 -0700 (PDT) Message-Id: <199808180354.UAA24421@freefall.freebsd.org> To: cvs-committers@FreeBSD.ORG, cvs-all@FreeBSD.ORG Subject: cvs commit: src/sys/ufs/ufs ufs_bmap.c Sender: owner-cvs-all@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk bde 1998/08/17 20:54:39 PDT Modified files: sys/ufs/ufs ufs_bmap.c Log: Quick fix for breakage of read clustering on non-IDE drives. Read clustering is obsolescent technology so hardly anyone noticed. On a DORS 32160 SCSI drive with 4 tags, read clustering makes very little difference even for huge sequential reads. However, on a ZIP SCSI drive with 0 tags, the minimum overhead per block is about 40 msec, so very large clusters must be used to get anywhere near the maximum transfer rate. Using clusters consisting of 1 8K block reduces the transfer rate to about 250K/sec. Under msdosfs, missing read clustering is normal and a cluster size of 1 512 byte block reduces the transfer rate to about 25K/sec. Broken in: rev.1.18 Revision Changes Path 1.22 +2 -2 src/sys/ufs/ufs/ufs_bmap.c