From: Andrea Arcangeli <andrea@novell.com>
To: Ryan Cumming <ryan@spitfire.gotdns.org>
Cc: Stelian Pop <stelian@popies.net>, Hugh Dickins <hugh@veritas.com>,
James R Bruce <bruce@andrew.cmu.edu>,
Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC, 2.6] a simple FIFO implementation
Date: Sat, 18 Sep 2004 00:00:39 +0200 [thread overview]
Message-ID: <20040917220039.GD15426@dualathlon.random> (raw)
In-Reply-To: <200409171454.02531.ryan@spitfire.gotdns.org>
On Fri, Sep 17, 2004 at 02:54:00PM -0700, Ryan Cumming wrote:
> On Friday 17 September 2004 14:28, Andrea Arcangeli wrote:
> > I also wonder if a O(1) algorithm exists to roundup to the next power of
> > two (doesn't come to mind by memory, hmm maybe it's not that easy
> > problem).
>
> Assuming that the architecture has an O(1) fls() function, this should work
> for non-zero values:
>
> inline unsigned int roundup(unsigned int x)
> {
> return (1 << fls(x));
> }
looks good, hardware helps here ;) really I was trying to do it with
math, not with hardware but sounds like this is the best we can do.
doing it with unsigned long retval and 1UL is probably better.
This is likely a candidate to go in include/linux/kernel.h (maybe under
the name roundup_pow_of_two to avoid misunderstanding with the much more
common PAGE_SIZE roundups)
thanks!
next prev parent reply other threads:[~2004-09-17 22:01 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-13 13:52 [RFC, 2.6] a simple FIFO implementation Stelian Pop
2004-09-15 10:20 ` Stelian Pop
2004-09-15 11:10 ` Tonnerre
2004-09-15 11:25 ` Alan Cox
2004-09-15 13:27 ` Dmitry Torokhov
2004-09-15 14:21 ` Stelian Pop
2004-09-15 22:30 ` Andrew Morton
2004-09-16 6:43 ` Stelian Pop
2004-09-16 7:04 ` Andrew Morton
2004-09-16 10:45 ` Stelian Pop
2004-09-16 13:57 ` Paul Jackson
2004-09-16 14:09 ` Stelian Pop
2004-09-16 15:45 ` Paul Jackson
2004-09-16 15:59 ` Stelian Pop
2004-09-16 15:09 ` Buddy Lucas
2004-09-16 15:29 ` Stelian Pop
2004-09-16 15:51 ` Buddy Lucas
2004-09-16 15:52 ` Stelian Pop
2004-09-16 16:07 ` Buddy Lucas
2004-09-16 18:30 ` Stelian Pop
2004-09-16 22:52 ` Buddy Lucas
2004-09-16 17:00 ` Andrew Morton
2004-09-16 18:09 ` Stelian Pop
2004-09-17 0:18 ` Andrew Morton
2004-09-17 10:24 ` Stelian Pop
2004-09-17 11:28 ` Paul Jackson
2004-09-17 11:44 ` Hugh Dickins
2004-09-17 12:24 ` Stelian Pop
2004-09-17 12:37 ` Duncan Sands
2004-09-17 12:48 ` Stelian Pop
2004-09-17 13:00 ` Duncan Sands
2004-09-17 13:05 ` Stelian Pop
2004-09-17 13:16 ` Duncan Sands
2004-09-17 13:15 ` Andrea Arcangeli
2004-09-17 13:36 ` Stelian Pop
2004-09-17 13:41 ` Andrea Arcangeli
2004-09-17 14:00 ` Stelian Pop
2004-09-17 15:14 ` Andrea Arcangeli
2004-09-17 14:47 ` Paul Jackson
2004-09-17 12:52 ` James R Bruce
2004-09-17 15:48 ` Stelian Pop
2004-09-17 16:01 ` Andrea Arcangeli
2004-09-17 16:14 ` Hugh Dickins
2004-09-17 20:50 ` Stelian Pop
2004-09-17 21:28 ` Andrea Arcangeli
2004-09-17 21:54 ` Ryan Cumming
2004-09-17 22:00 ` Andrea Arcangeli [this message]
2004-09-17 22:14 ` Ryan Cumming
2004-09-17 22:35 ` Andrew Morton
2004-09-18 0:07 ` Ryan Cumming
2004-09-17 22:29 ` Ryan Cumming
2004-09-18 3:41 ` Kyle Moffett
2004-09-18 7:56 ` Ryan Cumming
2004-09-17 22:07 ` Andrew Morton
2004-09-20 15:14 ` Stelian Pop
2004-09-20 18:01 ` Sasha Khapyorsky
2004-09-20 18:22 ` Stelian Pop
2004-09-20 19:00 ` Richard B. Johnson
2004-09-16 15:57 ` Bill Davidsen
2004-09-17 10:25 ` Stelian Pop
[not found] <260353727@toto.iv>
2004-09-17 1:00 ` Peter Chubb
2004-09-17 5:45 ` Chris Friesen
2004-09-17 11:58 ` Anton Blanchard
2004-09-17 10:32 ` Stelian Pop
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