From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Neil Conway <neilc(at)samurai(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Gaetano Mendola <mendola(at)bigfoot(dot)com>, "pgsql-patches(at)postgresql(dot)org" <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: equal() perf tweak |
Date: | 2003-11-12 03:04:05 |
Message-ID: | 200311120304.hAC345j29458@candle.pha.pa.us |
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Lists: | pgsql-hackers pgsql-patches |
Is there a TODO here?
---------------------------------------------------------------------------
Neil Conway wrote:
> Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> > This does suggest that it might be worth making the struct layout be
> >
> > int NodeTag;
> > int length;
> > foo *head;
> > foo *tail;
> >
> > since this would avoid some padding overhead on a machine where pointers
> > are 8 bytes and need 8-byte alignment. It probably doesn't help given
> > the current implementation of palloc, but why throw away padding
> > space?
>
> Interesting. I've heard in some shops it is standard policy to order
> the fields in all structs by their descending sizes (making allowances
> for platform-specific variations), so as to reduce padding. Do you
> think it would be worthwhile to systematically make this kind of
> reorganization throughout the backend?
>
> (Of course, we'd need to be weary of code that depends on order of the
> fields in structs, naturally -- such as the "NodeTag must be the first
> field" rule.)
>
> -Neil
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 7: don't forget to increase your free space map settings
>
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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