| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
| Cc: | Gregory Stark <stark(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Page-at-a-time Locking Considerations |
| Date: | 2008-02-05 09:31:00 |
| Message-ID: | 1202203860.4252.642.camel@ebony.site |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Mon, 2008-02-04 at 18:08 -0300, Alvaro Herrera wrote:
> Simon Riggs wrote:
> > On Mon, 2008-02-04 at 20:03 +0000, 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.
> >
> > There is a reason that's not been done... try it and see.
>
> What is it?
Time to locate a block differs in the two cases. clog requires a search
of data on 1 cache line, which isn't often changed. shared_buffers
requires a hash table search on a volatile data structure.
--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com
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