From owner-freebsd-hackers@FreeBSD.ORG Thu Sep 1 17:22:48 2011 Return-Path: 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 B35671065670; Thu, 1 Sep 2011 17:22:48 +0000 (UTC) (envelope-from asmrookie@gmail.com) Received: from mail-ww0-f42.google.com (mail-ww0-f42.google.com [74.125.82.42]) by mx1.freebsd.org (Postfix) with ESMTP id 20A618FC08; Thu, 1 Sep 2011 17:22:47 +0000 (UTC) Received: by wwe5 with SMTP id 5so1430731wwe.1 for ; Thu, 01 Sep 2011 10:22:47 -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:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type; bh=1y753kbTGsAQL94X6B5HzNupkkG/Gq0i5efPSLjFUOc=; b=r7/HRqiSPT2guGQv1RD430tr8/HJXWxMWW88kC8MkcgzITQX5SKSUwnwsTUpXLbjn1 rVhXG3+z035KAO5uybYYNdtpk4pZgzwLHhIrFEqhnMQHxEA/02/mRr/moSlC3gle9IWL GpI3rM93PMOFdIgJjwPwLcJSx9M9lkltQ7BP0= MIME-Version: 1.0 Received: by 10.227.28.70 with SMTP id l6mr95057wbc.34.1314897767048; Thu, 01 Sep 2011 10:22:47 -0700 (PDT) Sender: asmrookie@gmail.com Received: by 10.227.206.139 with HTTP; Thu, 1 Sep 2011 10:22:47 -0700 (PDT) In-Reply-To: References: <201108291415.32605.jhb@freebsd.org> <1314818323.2610.6.camel@hitfishpass-lx.corp.yahoo.com> Date: Thu, 1 Sep 2011 19:22:47 +0200 X-Google-Sender-Auth: AYs3JoteibTA095AEHTmBh0ZHSs Message-ID: From: Attilio Rao To: Ivan Voras Content-Type: text/plain; charset=UTF-8 Cc: "freebsd-hackers@freebsd.org" , Sean Bruno 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 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Sep 2011 17:22:48 -0000 2011/9/1 Ivan Voras : > On 1 September 2011 16:11, Attilio Rao 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? > Well, there are quite a few statically allocated, but as I said, making the kernel MAXCPU-agnostic (or sort of agnostic) is a goal and a good project. Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein