From: Jeffrey Carter <jeffrey.carter@boeing.com>
Subject: Re: Ada Tasks vs Linux processes
Date: Mon, 2 Apr 2001 22:17:26 GMT
Date: 2001-04-02T22:17:26+00:00 [thread overview]
Message-ID: <3AC8FA76.C6AD4B53@boeing.com> (raw)
In-Reply-To: 8H2y6.21501$ea6.2010619@news1.frmt1.sfba.home.com
tmoran@acm.org wrote:
>
> >As far as delay 0.0 is concerned, it should yield the CPU to another
> >task, if there's one ready to run. Generally, though, I use
> >delay Duration'Small instead of delay 0.0;
> LRM D.9(7) says the implementation must document the minimum delay
> value that actually causes the task to block, while D.9(5) says a
> delay of zero does not block, but is only "potentially blocking".
> Even among compilers that don't implement Annex D, delay 0.0 usually
> does not unnecessarily block, while any positive delay usually blocks
> for two clock ticks, which on some systems can be a surprisingly long
> time.
Indeed. The Verdix compiler for SCO UNIX responded to "delay
Duration'Small;" by delaying until the next clock tick. Since the clock
ticked at 1 Hz, this corresponded to an average delay of 0.5 seconds. I
saw some very slow code that resulted from the GRACE components using
"delay Duration'Small;" to obtain a unique timestamp.
Jeffrey Carter
next prev parent reply other threads:[~2001-04-02 22:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-04-01 15:27 Ada Tasks vs Linux processes Frank
2001-04-01 22:32 ` David C. Hoos, Sr.
2001-04-02 17:30 ` tmoran
2001-04-02 18:00 ` Robert A Duff
2001-04-02 18:20 ` Ehud Lamm
2001-04-02 22:17 ` Jeffrey Carter [this message]
2001-04-04 16:36 ` tmoran
2001-04-04 17:18 ` Gary Scott
2001-04-04 19:18 ` tmoran
2001-04-02 19:57 ` Frank
2001-04-03 11:28 ` Matthias Kretschmer
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