Re: [9fans] fossil periodic thread does zero sleep()

[cinap_lenrek@gmx.de]

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I have no idea what HZ is used on my kernel, but i think
i understand the problem now.

I still can reproduce it with this:

	double t, ct, ts;

	ct = nsec()*1e-6;
	t = ct + msec;

	for(;;){
		ts = t - ct;
		sleep(ts);
		ct = nsec()*1e-6;
		if(t <= ct){
			t += msec;
		}
	}

The problem is that when sleep is a little bit too fast on every round,
t will never catch up with ct. so it sleeps shorter and shorter until
t - ct < 1.

It all works when changing t += msec to t = ct + msec. It may still
do a zero sleep, but the error will not add up.

making new kernel...

--
cinap

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From: erik quanstrom <quanstro@quanstro.net>
To: 9fans@9fans.net
Subject: Re: [9fans] fossil periodic thread does zero sleep()
Date: Sun, 22 Mar 2009 20:24:17 -0400
Message-ID: <fb31fd1a5a64c0bf6f85af88838face3@quanstro.net>

what is your HZ set at?  after chasing a few bugs like this,
i've set HZ=1000.  actually i first saw the idea in sam hopins'
work  there's no performance drag and 1 ms
sleeps do actually sleep.

- erik