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Re: Calling conventions

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org, Matthew Wakeling <matthew(at)flymine(dot)org>
Subject: Re: Calling conventions
Date: 2009-07-17 16:34:29
Message-ID: 3159.1247848469@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
>> Does anyone have any ideas/opinions/statistics on what the performance
>> difference is between the two calling conventions?

> Version 1 is technically slower if you count the number of instructions,

That would be true if you compare version-0-to-version-0 calls (ie,
plain old C function call) to version-1-to-version-1 calling.  But
what is actually happening, since everything in the backend assumes
version 1, is that you have version-1-to-version-0 via an interface
layer.  Which is the worst of all possible worlds --- you have all
the overhead of a version-1 call plus the interface layer.

			regards, tom lane

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