linux-kernel - Re: [(RT RFC) PATCH v2 6/9] add a loop counter based timeout mechanism

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Date:	Mon, 25 Feb 2008 14:39:29 -0800
From:	Sven-Thorsten Dietrich <sdietrich@...ell.com>
To:	Pavel Machek <pavel@....cz>
Cc:	Gregory Haskins <ghaskins@...ell.com>, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, rostedt@...dmis.org,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	bill.huey@...il.com, kevin@...man.org, cminyard@...sta.com,
	dsingleton@...sta.com, dwalker@...sta.com, npiggin@...e.de,
	dsaxena@...xity.net, ak@...e.de, acme@...hat.com, gregkh@...e.de,
	pmorreale@...ell.com, mkohari@...ell.com
Subject: Re: [(RT RFC) PATCH v2 6/9] add a loop counter based timeout
	mechanism


On Mon, 2008-02-25 at 23:06 +0100, Pavel Machek wrote:
> On Mon 2008-02-25 11:01:08, Gregory Haskins wrote:
> > From: Sven Dietrich <sdietrich@...ell.com>
> 
> Why is this good idea?
> 

The timeout is useful to eliminate excessive CPU utilization when
waiting for long-held critical sections. 

The patch header should state this :) Will fix.

> > Signed-off-by: Sven Dietrich <sdietrich@...ell.com>
> > ---
> 
> >  
> > +config RTLOCK_DELAY
> > +	int "Default delay (in loops) for adaptive rtlocks"
> > +	range 0 1000000000
> > +	depends on ADAPTIVE_RTLOCK
> > +	default "10000"
> > +        help
> > +         This allows you to specify the maximum attempts a task will spin
> > +	 attempting to acquire an rtlock before sleeping.  The value is
> > +	 tunable at runtime via a sysctl.  A setting of 0 (zero) disables
> > +	 the adaptive algorithm entirely.
> > +
> 
> I believe you have _way_ too many config variables. If this can be set
> at runtime, does it need a config option, too?
> 

Absolutely. The sysctl was added after-the-fact, so this is a relic, we
will remove the config option, and define the default timeout in the
appropriate header.

Sven

> 									Pavel

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