[Top] [All Lists]

Re: Latest sources from CVS.

To: Dominic Sweetman <>
Subject: Re: Latest sources from CVS.
From: Ralf Baechle <>
Date: Sat, 7 Dec 2002 00:17:31 +0100
Cc: Thiemo Seufer <>, "Maciej W. Rozycki" <>, Carsten Langgaard <>, "Kevin D. Kissell" <>,
In-reply-to: <>; from on Fri, Dec 06, 2002 at 06:18:22PM +0000
Original-recipient: rfc822;
References: <> <> <> <> <>
User-agent: Mutt/
On Fri, Dec 06, 2002 at 06:18:22PM +0000, Dominic Sweetman wrote:

> > The first kernel was built as 64-bit ELF using 64-bit pointer and everything
> > 64-bit.  The second kernel was built using the -Wa,-32 trick.  That's over
> > 12% of bloat for full 64-bitiness which brings zero gain.
> Percentages are dangerous things.  This is 220Kbytes of memory, which
> currently represents an investment of about $0.05.  There may be
> embedded linux applications which care about 5c cost, but they
> probably won't use any variety of 64 bits...

I'd worry less if that was just 220kB of unused memory wasted.  But it's
actually inflated code, it's wasted i-cache and cycles.  220kB translates
to alost 7 times the size of today's typical 32kB i-cache.

Even if Thiemo was right this trick is probably the biggest micro-
optimization of the decade ...


<Prev in Thread] Current Thread [Next in Thread>