Re: profiling connection overhead

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: profiling connection overhead
Date: 2010-11-24 20:14:22
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Full results, and call graph, attached. The first obvious fact is
> that most of the memset overhead appears to be coming from
> InitCatCache.

AFAICT that must be the palloc0 calls that are zeroing out (mostly)
the hash bucket headers. I don't see any real way to make that cheaper
other than to cut the initial sizes of the hash tables (and add support
for expanding them later, which is lacking in catcache ATM). Not
convinced that that creates any net savings --- it might just save
some cycles at startup in exchange for more cycles later, in typical
backend usage.

Making those hashtables expansible wouldn't be a bad thing in itself,
mind you.

regards, tom lane

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