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From: pl@news.funet.fi.tut.fi (Lehtinen Pertti)
Newsgroups: comp.sys.amiga
Subject: Re: Multitasking (was re:Powermonger etc.)
Message-ID: <1990Dec13.083216.20087@funet.fi>
Date: 13 Dec 90 08:32:16 GMT
References: <9012130059.AA08767@ucbvax.Berkeley.EDU>
Sender: news@funet.fi (#News )
Organization: Finnish University and Research Network FUNET
Lines: 55


From article <9012130059.AA08767@ucbvax.Berkeley.EDU>, by i0046145@WATER.FIT.QUT.EDU.AU (Lukacz Alex):
> I've been having major problems with multitasking lately, anyone care to tell
> me what exactly is happening or a fix?
> 
> 1)  When using DiskMaster (V1.4) and NComm (V1.9) I often copy files or unarc
>     just-downloaded files while online.  Trouble is, when I try to get a 
>     directory (through the 1.3 'List' or 'Dir' commands) whilst unarcing is
>     taking place, the disk drive managed to 'crunch, crunch' back and forth
>     for MINUTES.
> 
> I think what is happening here is that the dir command is trying to get to the
> tracks around 880 for the list of files whilst the arcing program is still
> trying to unarc the program which would be spread over the tracks of the disk.
> 
> Now I think this is rather silly.  Surely one task should take priority over
> the other, so the 'dir' could intercept the unarcing and get the list of files
> and then let arc get back to work.
> 
> I have tried changing the task priority of 'dir' and 'list' but it doesn't seem
> to have much (read: any) effect.
> 

	I think your thougth is correct, driver get requests from programs
	alternating and so between every access there is long seek.

	While task waits for request to be filled, it is suspended and
	during dma read other (lower priority) task is switched in.
	So priorities don't play much role here, because both tasks get time
	anyway. Adding disk buffers could have more effect,
	but usually fileheader blocks are spread all over
	disk, so caching doesn't help much.
	
> 2)  When online a BBS or the VAX/UNIX, the text output to my monitor slows 
>     down IMMENSELY if I'm doing disk-accesses at the same time.  For example,
>     I'm looking for a particular file which I wish to upload.  I am certain
>     it is on one of two disks sitting in my disk-mailer.  I wish to get a 
>     directory of both disks so I can find out which one the file is on.  I
>     change windows to the CLI window and then issue 'dir'.  Click back to the
>     NComm window and SHAZAAM! - text output is slowed to an annoyingly slow
>     rate.  This happens both at 2400 and 9600 baud.
> 
> I have absolutely no idea of what is going on here.
>
 
	One reason could be interrupt blocking during certain disk accesses.
	This prevents serial driver from getting characters at 'usual' rate.

> 
> Any hints/solutions (no flames, send 'em to /dev/null) would be appreciated.
> 
> Alex.
pl@tut.fi				! All opinions expressed above are
Pertti Lehtinen				! purely offending and in subject
Tampere University of Technology	! to change without any further
Software Systems Laboratory		! notice