| From: | Atri Sharma <atri(dot)jiit(at)gmail(dot)com> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Merlin Moncure <mmoncure(at)gmail(dot)com> |
| Subject: | Re: Do we need so many hint bits? |
| Date: | 2012-11-19 18:43:06 |
| Message-ID: | CAOeZVicPMe6oP3QpQOn8mv8PpNeNHbACYiwHcb0Csrgdtb=0yQ@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Tue, Nov 20, 2012 at 12:08 AM, Jeff Davis <pgsql(at)j-davis(dot)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*
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Jeff Davis | 2012-11-19 18:46:37 | Re: Do we need so many hint bits? |
| Previous Message | Jeff Davis | 2012-11-19 18:38:50 | Re: Do we need so many hint bits? |