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Newsgroups: comp.sys.nsc.32k
Subject: Re: ten days with Minix
Message-ID: <9009102114.AA00790@manatee.UUCP>
Date: 11 Sep 90 01:14:22 GMT
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Good article, Karl.  
 
> In the past ten days I've spent a lot of time working on and
> with Minix, and I'm still as impressed as last time I wrote.
> But the road is far from smooth.  Here is a condensation of
> my notes which hopefully will help guide others along the path.
> 
> disk partitions
>     I've kept the partitions as Bruce built them, using hd3
[ stuff deleted ]

An additional suggestion:  Layout your partitions without regard
to the Version 1.3 32 Mbyte partition size limit.  That is if 
you ultimately want say several 50 Mbyte partitions, create 
a 30000 block partition, followed by a 20000 block gap, etc.
Hopefully, this will make the transformation to larger paritions
with verion 1.5 easier.

> multiple kernel images
>     You've got room for several kernels in the hd1 partition
>     so it's a nice idea to make a duplicate in case you screw
>     something up.  Use the ROM monitor to do this:
> 
> 	Command (? for help): read 0 2000 80
> 	Command (? for help): write 100 2000 80
> 
>     To run one of the kernels enter
> 
> 	Command (? for help): read X 2000 80
> 	Command (? for help): run 2000
> 
>     where X is either 0 or 100 depending on where you want
>     the main or the backup kernel image.

I consider this an absolute must at this point in time -- particularly
if you are modifing OS code.  The last thing you want is to find
out our new image will not run and you have on good OS images on-line.
The implication, of course, is to leave sufficent room at the 
beginning of the disk to hold two or more images each beginning
at convient block number.

> increase size of disk cache
>     Dave Rand suggested increasing the size of the disk cache
>     from 128 KB to 1 MB.  Assuming your Minix kernel source
>     lives in /usr/src/minix like mine does, look in fs/const.h
>     for a line like
> 
> 	#define NR_BUFS	128
> 
>     and change 128 to 1024.  Make sure that you do this in the
>     else part of the conditional.

You might want to also increase NR_BUFS_HASH accordingly.  I am 
not sure of what the best value is for NR_BUFS = 1024.  I arbitrarly
set mine to 1024.  Bruce Evans, a PC-Minix wizard from oz, has
NR_BUF = 320 and NR_HASH_BUF = 512 in his 32-bit 386 release.

> multiple tty lines

If you have a second terminal, you might want to direct printk
to this terminal.  It makes debugging or monitoring OS activity a 
lot cleaner. 

Best regards,
johnc


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