From owner-cvs-sys  Fri May  1 09:48:31 1998
Return-Path: <owner-cvs-sys>
Received: (from daemon@localhost)
          by hub.freebsd.org (8.8.8/8.8.8) id JAA10499
          for cvs-sys-outgoing; Fri, 1 May 1998 09:48:31 -0700 (PDT)
          (envelope-from owner-cvs-sys)
Received: from alpo.whistle.com (alpo.whistle.com [207.76.204.38])
          by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id JAA10479;
          Fri, 1 May 1998 09:48:16 -0700 (PDT)
          (envelope-from julian@whistle.com)
Received: (from daemon@localhost)
	by alpo.whistle.com (8.8.5/8.8.5) id JAA00218;
	Fri, 1 May 1998 09:45:20 -0700 (PDT)
Received: from current1.whistle.com(207.76.205.22)
 via SMTP by alpo.whistle.com, id smtpd000208; Fri May  1 16:45:11 1998
Date: Fri, 1 May 1998 09:39:37 -0700 (PDT)
From: Julian Elischer <julian@whistle.com>
To: Bruce Evans <bde@freebsd.org>
cc: cvs-committers@freebsd.org, cvs-all@freebsd.org, cvs-sys@freebsd.org
Subject: Re: cvs commit: src/sys/kern vfs_cluster.c
In-Reply-To: <199805011629.JAA15097@freefall.freebsd.org>
Message-ID: <Pine.BSF.3.95.980501093134.1869G-100000@current1.whistle.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-cvs-sys@freebsd.org
X-Loop: FreeBSD.org
Precedence: bulk

Talking of clusterring..

One problem with clustering is the fact that the flag that dissallows
CLUSTERING is stored in the BDEVSW entry. 

from sys/conf.h:
#define D_NOCLUSTERR 0x10000 /* disables cluter read */
#define D_NOCLUSTERW 0x20000 /* disables cluster write */
#define D_NOCLUSTERRW (D_NOCLUSTERR | D_NOCLUSTERW) 

 which is patently the wrong place for it. for several reasons: 

1/ different SCSI devices may have different ideas about clustering..
2/ in DEVFS/SLICE, all disks come in through the same major number/devfs[]
entry no matter which driver they eventually get passed to.
3/ [bc]devsw entries will totally go away anyhow.

 

On Fri, 1 May 1998, Bruce Evans wrote:

>   Log:
>   Partially fixed write clustering for cases where cluster_wbuild() is
>   called from vfs_bio_awrite() without going through cluster_write()
>   or ufs_bmaparray(), in particular for all writes to block disk devices.
>   Only ufs_bmaparray() sets vp->v_maxio in a correct way, and it doesn't
>   seem to be called early enough even for regular files.