From owner-freebsd-mips@FreeBSD.ORG  Thu Nov 15 21:07:35 2012
Return-Path: <owner-freebsd-mips@FreeBSD.ORG>
Delivered-To: mips@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
 by hub.freebsd.org (Postfix) with ESMTP id 4E357AE9
 for <mips@freebsd.org>; Thu, 15 Nov 2012 21:07:35 +0000 (UTC)
 (envelope-from imp@bsdimp.com)
Received: from mail-ob0-f182.google.com (mail-ob0-f182.google.com
 [209.85.214.182])
 by mx1.freebsd.org (Postfix) with ESMTP id 010008FC12
 for <mips@freebsd.org>; Thu, 15 Nov 2012 21:07:34 +0000 (UTC)
Received: by mail-ob0-f182.google.com with SMTP id 16so2680599obc.13
 for <mips@freebsd.org>; Thu, 15 Nov 2012 13:07:34 -0800 (PST)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
 d=google.com; s=20120113;
 h=sender:subject:mime-version:content-type:from:in-reply-to:date:cc
 :content-transfer-encoding:message-id:references:to:x-mailer
 :x-gm-message-state;
 bh=2/OxbfAa8raVrEoZZtgcrcCzXjlNwQAWrKKO4aR0qnY=;
 b=PLBhDHHzML6XiTclB/zr7tWk+ZCIz/fgTgkL7SpjfOOoRlrJ7QWZogc7CA8vp+uf1b
 VCE0pEPXutTPrkLMvdmbwjScZYg0SYBZQ+3tZP3RkgocPe2x/Qq030TSX7FoXoOECqI5
 Ak0hIqEhxH16r+zGyx/MKLaDHamxhoZVtVvYtZw0nh26kxo7l44jPfQRW4LbwjT0u6kl
 UTUaTDE+o58YF1V3a2j8IV5OrzFoO0xoqjd8NMZ8Ia22mLHKEbXBZTfUZr1p85DIGYrL
 Faz9/tGgN2NXB9B9QtIJGJuIbtR8UI18dfQ0M5n5ihH4g8W+PYOJ3paxd7lxM2XTViML
 ARzw==
Received: by 10.60.22.33 with SMTP id a1mr2033021oef.97.1353013654071;
 Thu, 15 Nov 2012 13:07:34 -0800 (PST)
Received: from [10.30.101.53] ([209.117.142.2])
 by mx.google.com with ESMTPS id l9sm13262195oec.5.2012.11.15.13.07.30
 (version=TLSv1/SSLv3 cipher=OTHER);
 Thu, 15 Nov 2012 13:07:31 -0800 (PST)
Sender: Warner Losh <wlosh@bsdimp.com>
Subject: Re: ZERO_REGION_SIZE
Mime-Version: 1.0 (Apple Message framework v1085)
Content-Type: text/plain; charset=us-ascii
From: Warner Losh <imp@bsdimp.com>
In-Reply-To: <50A54CCD.8070409@rice.edu>
Date: Thu, 15 Nov 2012 14:07:28 -0700
Content-Transfer-Encoding: quoted-printable
Message-Id: <DF2CB7FC-C1ED-4F4C-A39A-60B5E7FC566D@bsdimp.com>
References: <50A53391.4080909@rice.edu>
 <CAJ-Vmon-v3K7012ti_L6ao3wQHfQ99Jau1kJ+GhumbPjAuSDww@mail.gmail.com>
 <50A54CCD.8070409@rice.edu>
To: Alan Cox <alc@rice.edu>
X-Mailer: Apple Mail (2.1085)
X-Gm-Message-State: ALoCoQl7U0Sw0xoT9zVVzzJrs7WRACS7Kwj3mAa6WqnquAREnzlA9JaUrsm1wxtIiS0u8mUb/smK
Cc: "Jayachandran C." <jchandra@freebsd.org>, mips@freebsd.org
X-BeenThere: freebsd-mips@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Porting FreeBSD to MIPS <freebsd-mips.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-mips>,
 <mailto:freebsd-mips-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-mips>
List-Post: <mailto:freebsd-mips@freebsd.org>
List-Help: <mailto:freebsd-mips-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-mips>,
 <mailto:freebsd-mips-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 15 Nov 2012 21:07:35 -0000


On Nov 15, 2012, at 1:13 PM, Alan Cox wrote:
> P.S. I would encourage someone with hardware to look into implementing =
a
> non-iterative ffs*() using (d)clz.  The MIPS pmap would benefit from
> this.  Basically, most pmap_enter() calls are doing an ffs*().

ffs finds the first bit set. clz counts the number of leading zeros and =
thus finds the last bit set.  Would a non-iterative fls* be helpful?

Warner