Re: Do we need so many hint bits?
| От | Atri Sharma |
|---|---|
| Тема | Re: Do we need so many hint bits? |
| Дата | |
| Msg-id | CAOeZVicPMe6oP3QpQOn8mv8PpNeNHbACYiwHcb0Csrgdtb=0yQ@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Do we need so many hint bits? (Jeff Davis <pgsql@j-davis.com>) |
| Ответы |
Re: Do we need so many hint bits?
|
| Список | pgsql-hackers |
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:I thought mutexes are locks?
> 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.
>
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
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