Subject: Re: PG on NFS may be just a bad idea
From: Neil Conway <neilc@samurai.com>
To: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Bruce Momjian <bruce@momjian.us>, Tom Lane <tgl@sss.pgh.pa.us>,
	Simon Riggs <simon@2ndquadrant.com>,
	Josh Berkus <josh@agliodbs.com>, pgsql-hackers@postgresql.org,
	Mija Lee <mija@scharp.org>
In-Reply-To: <20071008205035.GF6000@alvh.no-ip.org>
References: <20071001234651.GD9430@alvh.no-ip.org>
	<200710082046.l98KkQj28574@momjian.us>
	<20071008205035.GF6000@alvh.no-ip.org>
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Date: Mon, 08 Oct 2007 14:22:17 -0700
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On Mon, 2007-10-08 at 16:50 -0400, Alvaro Herrera wrote:
> palloc uses malloc underneath.  My thought is to replace that with
> sbrk, mmap or something like that.  Not very portable though, a lot of
> work, and most likely not nearly enough benefits.

Yeah, I agree this isn't likely to be a win in the general case.
However, it would be interesting to explore a specialized allocator for
short-lived memory contexts, where we don't care about having an
effective pfree(). If the context is going to be reset or deleted
shortly anyway, we could probably optimize and simplify palloc() by
skipping free space accounting and then make pfree() a no-op. I recall
Tom mentioning something to this effect a few months back...

-Neil