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From: mutchler@zule.EBay.Sun (Dan Mutchler)
Newsgroups: comp.unix.internals
Subject: Re: Can Unix sleep in terms of mili/micro?
Message-ID: <MUTCHLER.90Sep11140510@zule.EBay.Sun>
Date: 11 Sep 90 21:05:10 GMT
References: <24437@adm.BRL.MIL> <84@dlss2.UUCP>
Sender: news@male.EBay.Sun.COM
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In-reply-to: james@dlss2.UUCP's message of 11 Sep 90 12:11:17 GMT

In article <84@dlss2.UUCP> james@dlss2.UUCP (James Cummings) writes:

   In article <24437@adm.BRL.MIL> TAYBENGH%NUSDISCS.BITNET@cunyvm.cuny.edu writes:
   >
   >        Can Unix sleep in terms of mili or mirco second? I am aware that
   >sleep() can only sleep in terms of second. Please specify the Unix Dialect
   >when u reply. Thanks.

	   How 'bout:

   main()
   {
	   sleep_less_than_sec(25);
	   exit(0);
   }

   sleep_less_than_sec(x)
   int x;
   {
	   int i;

	   for (i = 0;i <= x;i++)
		   ;
   }

	   I'd think that would give you approx. 25 clock cycles, dependent on
   the machine, the load on the machine, etc.

Unless a context switch occurs, which is quite possible. That may
still be okay if times much greater than 25 clock cycles are okay.
That is you need a sleep that sleeps at least x milliseconds.

Looping is in general a bad delay because different machines require
different CPU time to perform the loop. Intelligent use of macros can
help this, but unless it is in the kernel where a context switch
cannot occur you can only guareentee that you will not return before
the required delay.
--

Dan Mutchler                       | ARPA/Internet:  mutchler@EBay.Sun.COM
Sun Federal System Engineer        | UUCP:           ...!sun!mutchler
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