From owner-freebsd-isp  Wed Mar 12 20:55:24 1997
Return-Path: <owner-isp>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.5/8.8.5) id UAA04361
          for isp-outgoing; Wed, 12 Mar 1997 20:55:24 -0800 (PST)
Received: from scanner.worldgate.com (scanner.worldgate.com [198.161.84.3])
          by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id UAA04335;
          Wed, 12 Mar 1997 20:55:08 -0800 (PST)
Received: from znep.com (uucp@localhost) by scanner.worldgate.com (8.8.5/8.7.3) with UUCP id VAA23906; Wed, 12 Mar 1997 21:54:43 -0700 (MST)
Received: from localhost (marcs@localhost) by alive.znep.com (8.7.5/8.7.3) with SMTP id VAA25679; Wed, 12 Mar 1997 21:54:15 -0700 (MST)
Date: Wed, 12 Mar 1997 21:54:15 -0700 (MST)
From: Marc Slemko <marcs@znep.com>
To: Michael Hancock <michaelh@cet.co.jp>
cc: isp@FreeBSD.ORG, hackers@FreeBSD.ORG
Subject: Re: block and frag size for news (was Re: freebsd as a news server?)
In-Reply-To: <Pine.SV4.3.95.970313104650.24048C-100000@parkplace.cet.co.jp>
Message-ID: <Pine.BSF.3.95.970312215004.24128A-100000@alive.znep.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-isp@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

On Thu, 13 Mar 1997, Michael Hancock wrote:

> I used -a 8 to leave it at the default and as Bruce points out since the
> rotational delay now defaults to 0 the maxcontig setting probably doesn't
> matter.  It might matter I suppose if it actually goes thru the motion of
> triggering a rotational delay, even if it's 0, after every 8 blocks. 

/sys/ufs/ffs/ffs_alloc.c (from 2.2; 2.1 is different but does a similar
thing):

        /*
         * One or more previous blocks have been laid out. If less
         * than fs_maxcontig previous blocks are contiguous, the
         * next block is requested contiguously, otherwise it is
         * requested rotationally delayed by fs_rotdelay milliseconds.
         */
        nextblk = bap[indx - 1] + fs->fs_frag;
        if (fs->fs_rotdelay == 0 || indx < fs->fs_maxcontig ||
            bap[indx - fs->fs_maxcontig] +
            blkstofrags(fs, fs->fs_maxcontig) != nextblk)
                return (nextblk);
        /*
         * Here we convert ms of delay to frags as:
         * (frags) = (ms) * (rev/sec) * (sect/rev) /
         *      ((sect/frag) * (ms/sec))
         * then round up to the next block.
         */
        nextblk += roundup(fs->fs_rotdelay * fs->fs_rps * fs->fs_nsect /
            (NSPF(fs) * 1000), fs->fs_frag);
        return (nextblk);

To me, this says that if fs_rotdelay is 0 who cares about fs_maxcontig.