From owner-freebsd-questions@FreeBSD.ORG Wed Feb 3 03:18:24 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 5E8FF106566B for ; Wed, 3 Feb 2010 03:18:24 +0000 (UTC) (envelope-from listreader@lazlarlyricon.com) Received: from proxy3.bredband.net (proxy3.bredband.net [195.54.101.73]) by mx1.freebsd.org (Postfix) with ESMTP id 1C4828FC0C for ; Wed, 3 Feb 2010 03:18:24 +0000 (UTC) Received: from ipb1.telenor.se (195.54.127.164) by proxy3.bredband.net (7.3.140.3) id 4AD3E1BA02D6E0AD for freebsd-questions@freebsd.org; Wed, 3 Feb 2010 04:18:22 +0100 X-SMTPAUTH-B2: X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AuQ6ALt5aEtV44PPPGdsb2JhbACBM4ZTky8BAQEBN71shEUE X-IronPort-AV: E=Sophos;i="4.49,395,1262559600"; d="scan'208";a="32213190" Received: from c-cf83e355.09-42-6e6b7010.cust.bredbandsbolaget.se (HELO lazlar.kicks-ass.net) ([85.227.131.207]) by ipb1.telenor.se with ESMTP; 03 Feb 2010 04:18:22 +0100 Message-ID: <4B68EAFD.5070400@lazlarlyricon.com> Date: Wed, 03 Feb 2010 04:18:21 +0100 From: Rolf Nielsen User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.9.1.7) Gecko/20100201 Thunderbird/3.0.1 MIME-Version: 1.0 To: FreeBSD Questions Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: kmem_size / arc_max ratio X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Feb 2010 03:18:24 -0000 Hello everyone, I recently installed more RAM in my computer; increased it from 4GB to 8GB. Mainly to be able to use a larger arc for zfs. Now my question is, how much memory does the kernel need apart from the arc? I currently have kmem_size_max 512MB bigger than arc_max. I haven't run into any problems so far. I use my computer as desktop only, running WindowMaker and normally having xconsole, emiclock, firefox with 5+ tabs, thunderbird, amsn, sunbird, thunar, ktorrent and upto 5 or 6 xterms. My loader.conf looks like this: vfs.root.mountfrom="zfs:sysroot" vm.kmem_size_max=5G vm.kmem_size=5G vfs.zfs.arc_max=4608M vm.pmap.pg_ps_enabled=1 zfs_load="YES" nvidia_load="YES" I am considering increasing kmem_size, kmem_size_max and arc_max by 1024MB each. The idea behind that, is that when I had 4GB RAM I had kmem_size and kmen_size_max set to 2GB and never had any trouble with user memory running out, so I believe 2GB user memory should still be enough. Please correct me if I'm wrong. ;) Anyway, the main question is, should 512MB difference between kmem and arc be enough, or should I increase it? Or could I even decrease it? I've had very noticably increased performance with larger arc size, so I would like to set it as high as possible without causing problems for or degradation of other kernel tasks and/or user applications. Please let me know if you need any further information about my system. Cheers, Rolf Nielsen