From: David Miller <davem@davemloft.net>
To: zenczykowski@gmail.com
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH] net: pfifo_fast - use ffs(x)-1 instead of array lookup
Date: Tue, 13 Mar 2012 00:25:59 -0700 (PDT) [thread overview]
Message-ID: <20120313.002559.340117447102423900.davem@davemloft.net> (raw)
In-Reply-To: <CAHo-OoyWH9v+D7yJp3sAKnmUEp_DiTeDhmgPme2dGoqWGa2qjg@mail.gmail.com>
From: Maciej Żenczykowski <zenczykowski@gmail.com>
Date: Tue, 13 Mar 2012 00:23:27 -0700
> I was actually leaning towards going with ffs()-1, since
>
> it's excellent on x86-64
> good on x86_cmov
> decent on x86
> good on armv5+
>
> and I'm guessing it'll be good or better on any modern platform
Cycle count it with the pure integer operation variant, I bet it's
within a cycle or two, and at that point we're just splitting hairs
for an ugly-as-sin ifdef.
next prev parent reply other threads:[~2012-03-13 7:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-13 5:12 [PATCH] net: pfifo_fast - use ffs(x)-1 instead of array lookup Maciej Żenczykowski
2012-03-13 5:13 ` Maciej Żenczykowski
2012-03-13 5:54 ` David Miller
2012-03-13 7:21 ` Maciej Żenczykowski
2012-03-13 7:23 ` Maciej Żenczykowski
2012-03-13 7:25 ` David Miller [this message]
2012-03-13 7:25 ` David Miller
2012-03-13 11:04 ` David Laight
2012-03-13 16:55 ` David Laight
2012-03-13 17:34 ` Eric Dumazet
2012-03-13 20:37 ` Maciej Żenczykowski
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