Re: [PATCHES] Reorganization of spinlock defines

Marc G. Fournier wrote:
> 
> 
> On Fri, 12 Sep 2003, Tom Lane wrote:
> 
> > "Marc G. Fournier" <scrappy@postgresql.org> writes:
> > >> If we force people to give a --without-spinlocks config option to build
> > >> that way, then `pg_config --configure' will reveal the dirty deed ...
> >
> > > That's not quite what I meant :)  Right now, if I understood what Bruce
> > > was saying, if someone doesn't have spinlocks, it switches to using SysV
> > > Messenging, correct?  In the current system, is there anything that one
> > > can do on a running, live system, to detect that you aren't using
> > > spinlocks?
> >
> > It'll be fairly obvious if you use "ipcs -s" and count up the number of
> > semaphores created by the postmaster.  Ordinarily we will grab
> > approximately max_connections semas, but without spinlocks it will
> > be somewhere north of max_connections + 2 * shared_buffers ...
> 
> 'K, now, I know we acquire all our shared_buffers on startup now ... do we
> do the same with semaphores?  Or do they only grow as connections grow?
> If we do acquire at the start, would it not be trivial to add a message to
> the startup messages, based on #_of_semaphores != max_connections, that
> tells ppl that spinlocks aren't being used?

But why not warn at compile time.

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