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Date:      Thu, 5 Oct 1995 17:09:04 -0700 (MST)
From:      Terry Lambert <terry@lambert.org>
To:        bmk@dtr.com
Cc:        serges@umr.edu, freebsd-questions@freefall.freebsd.org
Subject:   Re: tunefs
Message-ID:  <199510060009.RAA05011@phaeton.artisoft.com>
In-Reply-To: <199510052330.QAA00567@everest> from "bmk@dtr.com" at Oct 5, 95 04:30:51 pm

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> > Is there a way under FBSD to 'tunefs' the / filesystem, WITHOUT
> > creating another filesystem and without making an existing filesystem
> > bootable? 
> 
> (This is all to the best of my knowledge.  I may be wrong.  You've been
> warned. :)
> 
> You must can only tunefs a dismounted filesystem - so you must do one of
> a few things:

Oh heck; I forgot that I had hacked that.

The main problem is getting the tuning changes into the in-core copy of
the struct so that it effects subsequent operations on the FS in question.

The -current code can't do this, so that's why the mount/remount.

The fix is to replace the read/write interface with an in/out ioctl()
interface.

You could just update the in core copy without too much problem, since
it's synced to disk on unmount.

I did this because I was trying to find optimal tuning parameters for a
particular benchmark and got tired of the mount/unmount.

If it's all the same with you, I'd like to hack on the logical device
management using Julians new devfs once that's all the way up before
rolling changes in -- that way  I won't have to hack them multiple
times after they're committed.

I've been hacking logical volume management for partitions, extended
partitions and BSD extended partitions (ie: the results of disklabel)
for a port, and I'd like to get it all rolled together first.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.



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