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Date:      Thu, 02 Dec 1999 16:50:28 +0100
From:      Marcel Moolenaar <marcel@scc.nl>
To:        Ville-Pertti Keinonen <will@iki.fi>
Cc:        bde@zeta.org.au, current@freebsd.org, dillon@apollo.backplane.com
Subject:   Re: kernel: -mpreferred-stack-boundary=2 ??
Message-ID:  <38469544.FBA70F80@scc.nl>
References:  <19991202150047.5370.qmail@ns.demophon.com>

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Ville-Pertti Keinonen wrote:
> 
> If the pessimization persists when the initial alignment is fixed,
> then there's a trade-off between a small pessimization for typical
> code and a big pessimization for less common (but more often
> performance-critical) code.

Performance critical code should always be coded and compiled in such a
way that the machine code is optimal (for whatever optimal means in this
case). It doesn't really make sense to argue how default compiler
settings affect the performance critical code, because default compiler
settings are per definition set to suit the majority of the programs.
With 16 byte alignment and even with 8 byte alignment, defaults are not
set for the majority of the programs, but clearly for the special cases.
That's why I want 4 byte alignments by default and 8 or 16 byte
alignments explicitely set for the special cases.

Anyway, enough said. This has already taken enough bandwidth without any
intent to change anything :-)

-- 
Marcel Moolenaar                        mailto:marcel@scc.nl
SCC Internetworking & Databases           http://www.scc.nl/
The FreeBSD project                mailto:marcel@FreeBSD.org


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