Re: Do we need so many hint bits?

On Tue, Nov 20, 2012 at 12:08 AM, Jeff Davis <pgsql@j-davis.com> wrote:

> On Mon, 2012-11-19 at 23:50 +0530, Atri Sharma wrote:
>
> > Sorry If I am being a bit naive, but shouldnt a simple mutex work in
> > the case when a process wants to change the VM bit in cache?
> >
> > Mutex would be cheaper than locks.
> >
> I thought mutexes are locks?
>
> The point is to avoid taking new locks (or mutexes) during a read of the
> VM bit, because there is concern that it could cause contention. If we
> lock the entire VM page, that represents many, many data pages, so it's
> worrisome.
>
> Regards,
>         Jeff Davis
>
>
>
My mistake...I thought we were more concerned about the cost of locking.

I agree, locking many data pages simultaneously could be hazardous.

This requires more thought.Maybe removing PD_ALL_VISIBLE isnt such a great
idea after all...

Atri

-- 
Regards,

Atri
*l'apprenant*