| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [RFC, POC] Don't require a NBuffer sized PrivateRefCount array of local buffer pins |
| Date: | 2014-04-09 14:30:50 |
| Message-ID: | 20140409143050.GK4161@awork2.anarazel.de |
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| Lists: | pgsql-hackers |
On 2014-04-09 10:26:25 -0400, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > It's not unreasonable to argue that we just shouldn't optimize for
> > several pins held by the same backend for the same and always touch the
> > global count.
>
> NAK.
Note I didn't implement it because I wasn't too convinced either ;)
> That would be a killer because of increased contention for buffer
> headers. The code is full of places where a buffer's PrivateRefCount
> jumps up and down a bit, for example when transferring a tuple into a
> TupleTableSlot.
On the other hand in those scenarios the backend is pretty likely to
already have the cacheline locally in exclusive mode...
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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