Re: SSI patch version 14

From: Markus Wanner <markus(at)bluegap(dot)ch>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: David Fetter <david(at)fetter(dot)org>, Dan Ports <drkp(at)csail(dot)mit(dot)edu>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, simon(at)2ndquadrant(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: SSI patch version 14
Date: 2011-02-09 19:51:44
Message-ID: 4D52F050.7050504@bluegap.ch
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On 02/09/2011 06:25 PM, Robert Haas wrote:
> On Wed, Feb 9, 2011 at 10:38 AM, Markus Wanner <markus(at)bluegap(dot)ch> wrote:
>> Thread based, dynamically allocatable and resizeable shared memory, as
>> most other projects and developers use, for example.

I didn't mean to say we should switch to that model. It's just *the*
other model that works (whether or not it's better in general or for
Postgres is debatable).

> Or less invasively, a small sysv shm to prevent the double-postmaster
> problem, and allocate the rest using POSIX shm.

..which allows ftruncate() to resize, right? That's the main benefit
over sysv shm which we currently use.

ISTM that addresses the resizing-of-the-overall-shared-memory question,
but doesn't that require dynamic allocation or some other kind of
book-keeping? Or do you envision all subsystems to have to
re-initialize their new (grown or shrunken) chunk of it?

Regards

Markus Wanner

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