Re: Page-at-a-time Locking Considerations

Tom Lane wrote:

> > Gregory Stark wrote:
> >> I wonder how hard it would be to shove the clog into regular shared memory
> >> pages and let the clock sweep take care of adjusting the percentage of shared
> >> mem allocated to the clog versus data pages.

> My recollection is that we didn't do that because the standard buffer
> manager has some assumptions that are violated by clog/etc pages ---
> notably the lack of LSNs on the pages. Not sure how hard that is to
> fix. I also note that we'd not really be removing any contention,
> rather just pushing it into the bufmgr. Maybe the bufmgr is now
> scalable enough that it could take the extra load better than SLRU can,
> but this is hardly a given.

Well, in the case of pg_subtrans, I don't think the problem is
contention -- rather, the fact that the number of buffers is fixed and
small.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.