| From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
|---|---|
| To: | Scott Carey <scott(at)richrelevance(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)sun(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Proposal of tunable fix for scalability of 8.4 |
| Date: | 2009-03-20 15:46:01 |
| Message-ID: | 20090320154601.GC8313@alvh.no-ip.org |
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| Thread: | |
| Lists: | pgsql-performance |
Scott Carey escribió:
> Your description (much of which I cut out) is exactly how I understood
> it until Simon Riggs' post which changed my view and understanding.
> Under that situation, waking all shared will leave all XXXXX at the
> front and hence alternate shared/exclusive/shared/exclusive as long as
> both types are contending. Simon's post changed my view. Below is
> some cut/paste from it:
Simon's explanation, however, is at odds with the code.
http://git.postgresql.org/?p=postgresql.git;a=blob;f=src/backend/storage/lmgr/lwlock.c
There is "queue jumping" in the regular (heavyweight) lock manager, but
that's a pretty different body of code.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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