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From: alan@shodha.dec.com ( Alan's Home for Wayward Notes File.)
Newsgroups: comp.unix.ultrix
Subject: Re: Tuning up an Ultrix system? HELP
Summary: Attack of the killer interrupts.
Message-ID: <754@shodha.dec.com>
Date: 22 Feb 90 17:06:21 GMT
References: <5383@okstate.UUCP> <722@shodha.dec.com> <1872@wheaton.UUCP>
Organization: Digital Equipment Corp. - Colorado Springs, CO.
Lines: 47

In article <1872@wheaton.UUCP>, stefan@wheaton.UUCP (Stefan Brandle ) writes:

>  r b w   avm  fre  re at  pi  po  fr  de  sr r0 r2 x2 x3  in  sy  cs us sy id
>  2 0 0   671 5911   0  0   0   0   0   0   0  2  0  0  0  85  73  14 10 20 70
>  1 1 0   710 5865   0  0   0   0   0   0   0  2  0  0  0 901 256  10  5 65 31
>  1 0 0   313 5865   0  0   0   0   0   0   0  0  0  0  0 950 262   9  7 80 13
>  1 0 0   542 5865   0  0   0   0   0   0   0  1  1  0  0 956 268  10  6 84  9
>  1 0 0   476 5865   0  0   0   0   0   0   0  1  3  0  0 475 147  26  6 76 18

	I may have previously commented that I didn't have the
	experience in determining when the number of interupts
	was "too many".  Sometimes though it's pretty obvious.
	The real question though is where are they all coming
	from?  The first place I'd look at this point is to what
	the tty I/O is like.  Does seem be a relationship between
	the high number of interrupts and either tty input or tty
	output?  (Use iostat(1) to look at tty I/O).

	What are you using the console port for?  Keep it find that
	the console interface is real braindead serial line.  Every
	character input or output over it causes an interrupt.

>  procs     memory                       page      disk  faults          cpu
>  r b w   avm  fre  re at  pi  po  fr  de  sr r0 r2 x2 x3  in  sy  cs us sy id
>  1 0 0  1066 5787   4 10   5   0   0   0   0  3  1  0  0 491 205  25 19 75  7

	The paging blip is probably somebody starting up a program.
> 
> I can reschedule news--I know how to do that--but wonder whether 
> there is anything else that can be modified kernel-wise that will make a 
> significant difference.  My guess is no, but maybe somebody has ideas.

	Unfortunately there is very little in the kernel that can be
	"tuned".  What you usually have to do is look at all the
	different *stat programs to find out where the bottlenecks
	or problems are and then see if you can get rid of them or
	balance around them.
> 
> -stefan
> -- 
> ------------------------------------------- MA Bell: (708) 260-5019 ---------
> Stefan Brandle                UUCP: ...!{obdient,uunet!tellab5}!wheaton!stefan
> Wheaton College			or	stefan@wheaton.UUCP
> Wheaton, IL 60187 		"But I never claimed to be sane!"

-- 
Alan Rollow				alan@nabeth.enet.dec.com