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From: richard@locus.com (Richard M. Mathews)
Newsgroups: comp.unix.aix
Subject: Re: Does AIX have a function like sginap()?
Message-ID: <richard.668491618@fafnir.la.locus.com>
Date: 9 Mar 91 04:06:58 GMT
References: <MCCALPIN.91Mar7210817@pereland.cms.udel.edu>
Organization: Locus Computing Corporation, Los Angeles, California
Lines: 26

mccalpin@perelandra.cms.udel.edu (John D. McCalpin) writes:

>The modified code segment:
>	OPEN(in_unit,....)
> 8888	idummy = sginap(0)
>	READ(in_unit,ERR=8888,END=8888) data
>	CLOSE(in_unit)
>runs much more efficiently.

>I cannot use the normal 'sleep()' routines, since the actual latencies
>involved are much smaller than 1 second, and the OPEN/READ/CLOSE
>sequence needs to be done several times per second.

Any system call should have the property of giving up control to a
higher priority process.  I am almost certain that is true in AIX/370
and AIX PS/2.  I am less certain on the 6000.  Try getpid().  (Or
does sginap go farther and explicitly put you at a low priority?)

Better yet, can you use select()?  This will let you sleep until
there is data available -- no shorter, no longer (ignoring the time
it takes for you to make it to the front of the run queue).

Richard M. Mathews			 Freedom for Lithuania
richard@locus.com				Laisve!
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