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Message-ID: <16714.14118.212946.499226@wombat.chubb.wattle.id.au>
Date: Fri, 17 Sep 2004 11:00:22 +1000
From: Peter Chubb <peterc@gelato.unsw.edu.au>
To: Andrew Morton <akpm@osdl.org>
Cc: Stelian Pop <stelian@popies.net>, linux-kernel@vger.kernel.org
Subject: Re: [RFC, 2.6] a simple FIFO implementation
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>>>>> "Andrew" == Andrew Morton <akpm@osdl.org> writes:


Andrew> All the struct needs is `head', `tail' and
Andrew> `number_of_bytes_at_buf', all unsigned.

Andrew> add(char c) {
Andrew>       p-> buf[p->head++ % p->number_of_bytes_at_buf] = c;
Andrew> }

This depends on how expensive % is.  On IA64, something like this:

     add(char c) {
	     int i = p->head == p->len ? p->head++ : 0;
	     p->buf[i] = c;
     }

is cheaper, as % generates a subroutine call to __modsi3.  It also is
shorter =-- 12 bundles as opposed to 15.
     

-- 
Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
The technical we do immediately,  the political takes *forever*
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