From owner-freebsd-hackers@FreeBSD.ORG  Thu Sep  1 14:59:12 2011
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 1F0D7106566B;
	Thu,  1 Sep 2011 14:59:12 +0000 (UTC)
	(envelope-from ivoras@gmail.com)
Received: from mail-yw0-f54.google.com (mail-yw0-f54.google.com
	[209.85.213.54])
	by mx1.freebsd.org (Postfix) with ESMTP id BB91A8FC14;
	Thu,  1 Sep 2011 14:59:11 +0000 (UTC)
Received: by ywo32 with SMTP id 32so1838439ywo.13
	for <multiple recipients>; Thu, 01 Sep 2011 07:59:11 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma;
	h=mime-version:sender:in-reply-to:references:from:date
	:x-google-sender-auth:message-id:subject:to:cc:content-type;
	bh=MCh8OfYfFkYYRI9fr6pSZZ+V+ZfdK+Ye9wEXe6p+e9c=;
	b=LCt5GNxbwazmJvpWKX0Wb0m9c/OWjmHUPHRCtEU2G3Wz1RBNf1XdGA93mq4jCK8wAY
	tx7LJc0+51xumNsWrIeNjIu9QrvWJcxFZyDuwqGX4lbio0hhRZ+64uoxTC8G2AKwihfA
	a1Vzf23hGvPcOW8M8ztyYvstZcUykmHBZU2TQ=
Received: by 10.101.5.21 with SMTP id h21mr300663ani.123.1314889151163; Thu,
	01 Sep 2011 07:59:11 -0700 (PDT)
MIME-Version: 1.0
Sender: ivoras@gmail.com
Received: by 10.100.134.4 with HTTP; Thu, 1 Sep 2011 07:58:31 -0700 (PDT)
In-Reply-To: <CAJ-FndCbXs0btQUc8_L3F4kcsdu5WN-75HY+hdKY+5OGhase2Q@mail.gmail.com>
References: <j38lj5$s9a$1@dough.gmane.org>
	<CAMBSHm_Sv_KZUs4h-tDGAZCq8s2qo_bMmfZxLbVkcH1=_Wu0OQ@mail.gmail.com>
	<CAF-QHFW=aU3=iKE9WMg6+D6eP9OXth=c0AidBc140ykmAPD2zg@mail.gmail.com>
	<201108291415.32605.jhb@freebsd.org> <j3ju8s$kuo$2@dough.gmane.org>
	<1314818323.2610.6.camel@hitfishpass-lx.corp.yahoo.com>
	<CAJ-FndCbXs0btQUc8_L3F4kcsdu5WN-75HY+hdKY+5OGhase2Q@mail.gmail.com>
From: Ivan Voras <ivoras@freebsd.org>
Date: Thu, 1 Sep 2011 16:58:31 +0200
X-Google-Sender-Auth: TH08ThmvnU5Jq1-Xkz_0YCHQHr0
Message-ID: <CAF-QHFUCYJL28GxQu_=QjGgiBOVumNK56tO2rnmmTo4++jf0yw@mail.gmail.com>
To: Attilio Rao <attilio@freebsd.org>
Content-Type: text/plain; charset=UTF-8
Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>,
	Sean Bruno <seanbru@yahoo-inc.com>
Subject: Re: Large machine test ideas
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 01 Sep 2011 14:59:12 -0000

On 1 September 2011 16:11, Attilio Rao <attilio@freebsd.org> wrote:

>> I mean, if we have 2 cpus in a machine, but MAXCPU is set to 256, there
>> is a bunch of "lost" memory and higher levels of lock contention?
>>
>> I thought that attilio was taking a stab at enhancing this, but at the
>> current time anything more than a value of 64 for MAXCPU is kind of a
>> "caveat emptor" area of FreeBSD.
>
> With newest current you can redefine MAXCPU in your kernel config, so
> you don't need to bump the default value.
> I think 64 as default value is good enough.
>
> Removing MAXCPU dependency from the KBI is an important project
> someone should adopt and bring to conclusion.

That's certainly one half of it and thanks for the work, but the real
question in this thread is what Sean asked: what are the negative
side-effects of simply bumping MAXCPU to 256 by default? AFAIK, there
are not that many structures which are statically sized by MAXCMPU and
most use the runtime-detected smp_cpus?