Date: Sun, 3 Feb 2002 19:29:57 +0100 From: Miguel Mendez <flynn@energyhq.homeip.net> To: Alfred Perlstein <bright@mu.org> Cc: mime@traveller.cz, hackers@freebsd.org Subject: Re: stack alignment issues (was: unbelievable benchmark output) Message-ID: <20020203192957.4ce563a0.flynn@energyhq.homeip.net> In-Reply-To: <20020203085941.N10817@elvis.mu.org> References: <Pine.BSF.4.41.0202021843210.5132-100000@prg.traveller.cz> <20020203085941.N10817@elvis.mu.org>
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On Sun, 3 Feb 2002 08:59:41 -0800
Alfred Perlstein <bright@mu.org> wrote:
Hi,
> It sure looks like an alignment issue. If you print the address
> of 'i' and 'j' in the attached program you can see for the fast
> case they are aligned to 8 byte boundries, but when it's slow they
> are at an address that is a multiple of 4 but not 8.
Agreed, my bet is on data alignment.
>
> Not really sure what to make of this, anyone else know how we ought
> to fix this?
Well, you could always malloc() some memory and make sure your data is in an address that is multiple of 8. You'll waste some mem but will gain performance. I actually haven't tried it on FreeBSD but it's a trick I used to do on the Amiga some years ago.
Cheers,
--
Miguel Mendez - flynn@energyhq.homeip.net
Public Key :: http://energyhq.homeip.net/files/pubkey.txt
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