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Date:      Mon, 1 Mar 1999 17:22:34 -0800 (PST)
From:      Tom <tom@uniserve.com>
To:        Andrew McNaughton <andrew@squiz.co.nz>
Cc:        freebsd-stable@FreeBSD.ORG
Subject:   Re: rc5des slows tape thruput 
Message-ID:  <Pine.BSF.4.02A.9903011720030.20468-100000@shell.uniserve.ca>
In-Reply-To: <199903020010.NAA09186@aniwa.sky>

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On Tue, 2 Mar 1999, Andrew McNaughton wrote:

> >   Maybe, maybe not.  There are device driver issues with scheduling and
> > CPU utilization, and with block sizes, and buffering capacity of the
> > driver and device.  Also an IO bound process will yield to the scheduler a
> > lot, and since rc5des is probably never blocked, and it will always take
> > slice.  If you tape requires another block at that moment, it is just
> > going to have to wait.
> 
> So, if rc5des is idprio'ed and the tape process blocks on IO, the
> rc5des process doesn't run?  Or does the tape process just get control
> back quicker when the IO block goes away?

  I was talking about niced processes.  The realtime scheduling used by
idprio/rtprio is completely different.

> Do you know where I could find detailed docs on this?  The man pages
> fall short.

  I'm not sure.  

> Andrew


Tom
Systems Support
Uniserve



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