Thread

Re: [HACKERS] spin locks

Jordan Henderson <jordanh@ccia.com> — 1998-02-16T02:05:09Z

Folks,

On the spin lock and multiple CPU's, this should not be
a compile time issue, but a runtime issue. What do you 
think?

Jordan Henderson

Re: [HACKERS] spin locks

Marc Fournier <scrappy@hub.org> — 1998-02-16T02:18:59Z

On Sun, 15 Feb 1998, Jordan Henderson wrote:

> Folks,
> 
> On the spin lock and multiple CPU's, this should not be
> a compile time issue, but a runtime issue. What do you 
> think?

	And you are proposing...?

Marc G. Fournier                                
Systems Administrator @ hub.org 
primary: scrappy@hub.org           secondary: scrappy@{freebsd|postgresql}.org

Re: [HACKERS] spin locks

Jordan Henderson <jordanh@ccia.com> — 1998-02-16T14:21:34Z

Folks,

On the thread in regards to spinlocks and multiple CPU's.
The line of thought appeared to be select a compile
time option to determine behavior, and whether to yield or not.

I am thinking that if it comes to having alternate code, the
system should be able to make the determination at runtime,
not compile time. I don't know if all of the platforms supported
have a version of the sysinfo utility, but here is how, at runtime
it gets the number of CPUS available:

**** EXCERPTED FROM SYSINFO SOURCE 3.3.1 ****
/*
 * Use sysconf() to find number of CPU's.
 */
extern char *GetNumCpuSysconf()
{
    int				Num = -1;
    static char		       *NumStr = NULL;

    if (NumStr)
	return(NumStr);

#if	defined(_SC_NPROCESSORS_CONF)
    Num = (int) sysconf(_SC_NPROCESSORS_CONF);
    if (Num >= 0) {
	NumStr = itoa(Num);
	if (NumStr)
	    NumStr = strdup(NumStr);
    }
#endif	/* _SC_NPROCESSORS_CONF */

    return(NumStr);
}

What I would propose, if the decision is made to yield,
that at initialization time, the number of CPU's available
are determined, and a flag set, or, an indirect jump
changed. This would allow the software to have both
personalities, depending on which system it found it
self running on.

Thoughts?
Jordan Henderson

Re: [HACKERS] spin locks

Bruce Momjian <maillist@candle.pha.pa.us> — 1998-02-16T20:50:52Z

> 
> Folks,
> 
> On the spin lock and multiple CPU's, this should not be
> a compile time issue, but a runtime issue. What do you 
> think?
> 
> Jordan Henderson
> 
> 
> 

Yes.

-- 
Bruce Momjian
maillist@candle.pha.pa.us

Re: [HACKERS] spin locks

Massimo Dal Zotto <dz@cs.unitn.it> — 1998-02-16T22:33:00Z

> 
> > 
> > Folks,
> > 
> > On the spin lock and multiple CPU's, this should not be
> > a compile time issue, but a runtime issue. What do you 
> > think?
> > 
> > Jordan Henderson
> > 
> > 
> > 
> 
> Yes.

Yes, if we have the tprintf patch we can also add an option flag and change
it un the fly while the backends are running.

-- 
Massimo Dal Zotto

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