[Linux-cluster] Re: [PATCH 00/14] GFS

[Arjan van de Ven <arjan infradead org>]

On Thu, 2005-08-11 at 14:06 +0800, David Teigland wrote:
> On Tue, Aug 02, 2005 at 09:45:24AM +0200, Arjan van de Ven wrote:
> 
> > * +	if (create)
> > +		down_write(&ip->i_rw_mutex);
> > +	else
> > +		down_read(&ip->i_rw_mutex);
> > 
> > why do you use a rwsem and not a regular semaphore? You are aware that
> > rwsems are far more expensive than regular ones right?  How skewed is
> > the read/write ratio?
> 
> Rough tests show around 4/1, that high or low?

that's quite borderline; if it was my code I'd not use a rwsem for that
ratio (my own rule of thumb, based on not a lot other than gut feeling)
is a 10/1 ratio at minimum... but it's not so low that it screams for
removing it. However.... it might well make your code a lot simpler so
it might still be worth simplifying.