From: PFC <lists@boutiquenumerique.com>
To: stange@rentec.com
To: mark@mark.mielke.cc
Cc: Donald Courtney <Donald.Courtney@sun.com>
Cc: William Yu <wyu@talisys.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Caching by Postgres
Date: Wed, 24 Aug 2005 22:03:43 +0200
Message-ID: <op.sv03chd0th1vuj@localhost> (raw)
In-Reply-To: <430CC0AD.5040400@rentec.com>
References: <20050823171045.12112.qmail@web51309.mail.yahoo.com>
<20050823124323.710a9dd3.frank@wiles.org>
<430B6DE3.6040109@sun.com>
<deg68k$16gh$1@news.hub.org>
<430C7448.7030103@sun.com>
<20050824173055.GA11788@mark.mielke.cc>
<430CC0AD.5040400@rentec.com>
> At least on Sparc processors, v8 and newer, any double precision math
> (including longs) is performed with a single instruction, just like for
> a 32 bit datum. Loads and stores of 8 byte datums are also handled via
> a single instruction. The urban myth that 64bit math is
> different/better on a 64 bit processor is just that; yes, some lower
> end processors would emulate/trap those instructions but that an
> implementation detail, not architecture. I believe that this is all
> true for other RISC processors as well.
>
> The 64bit API on UltraSparcs does bring along some extra FP registers
> IIRC.
It's very different on x86.
64-bit x86 like the Opteron has more registers, which are very scarce on
the base x86 (8 I think). This alone is very important. There are other
factors as well.
> Solaris, at least, provided support for far more than 4GB of physical
> memory on 32 bit kernels. A newer 64 bit kernel might be more
> efficient, but that's just because the time was taken to support large
> page sizes and more efficient data structures. It's nothing intrinsic
> to a 32 vs 64 bit kernel.
Well, on a large working set, a processor which can directly address more
than 4GB of memory will be a lot faster than one which can't, and has to
play with the MMU and paging units !
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To: pgsql-performance@postgresql.org
Cc: lists@boutiquenumerique.com, stange@rentec.com, mark@mark.mielke.cc, Donald.Courtney@sun.com, wyu@talisys.com
Subject: Re: Caching by Postgres
In-Reply-To: <op.sv03chd0th1vuj@localhost>
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