Horton
Menu

Re: Do we need so many hint bits?

Andres Freund <andres@2ndquadrant.com>

View thread
From: Andres Freund <andres@2ndquadrant.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, pgsql-hackers@postgresql.org, Merlin Moncure <mmoncure@gmail.com>
Date: 2012-11-18T14:19:31Z
Lists: pgsql-hackers 
On Sunday, November 18, 2012 03:07:01 AM Jeff Davis wrote:
> Process A (process that clears a VM bit for a data page):
>   1. Acquires exclusive lock on data buffer
>   2. Acquires exclusive lock on VM buffer
>   3. clears VM bit
>   4. Releases VM buffer lock
>   5. Releases data buffer lock

Well, but right this is a rather big difference. If vm pages get 
unconditionally locked all the time we will have a huge source of new 
contention as they are shared between so many heap pages.

Andres
-- 
Andres Freund		http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services