From owner-freebsd-stable@FreeBSD.ORG Fri Jun 4 20:51:47 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id EDEB31065674; Fri, 4 Jun 2010 20:51:47 +0000 (UTC) (envelope-from alc@cs.rice.edu) Received: from mail.cs.rice.edu (mail.cs.rice.edu [128.42.1.31]) by mx1.freebsd.org (Postfix) with ESMTP id B483B8FC16; Fri, 4 Jun 2010 20:51:47 +0000 (UTC) Received: from mail.cs.rice.edu (localhost.localdomain [127.0.0.1]) by mail.cs.rice.edu (Postfix) with ESMTP id 45E682C2A8C; Fri, 4 Jun 2010 15:51:47 -0500 (CDT) X-Virus-Scanned: by amavis-2.4.0 at mail.cs.rice.edu Received: from mail.cs.rice.edu ([127.0.0.1]) by mail.cs.rice.edu (mail.cs.rice.edu [127.0.0.1]) (amavisd-new, port 10024) with LMTP id poboG2QnedAa; Fri, 4 Jun 2010 15:51:39 -0500 (CDT) Received: from [10.209.194.87] (unknown [10.209.194.87]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.cs.rice.edu (Postfix) with ESMTP id 5134A2C2B32; Fri, 4 Jun 2010 15:51:39 -0500 (CDT) Message-ID: <4C09674C.10009@cs.rice.edu> Date: Fri, 04 Jun 2010 15:51:24 -0500 From: Alan Cox User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.1.9) Gecko/20100317 Thunderbird/3.0.4 MIME-Version: 1.0 To: John Baldwin References: <201005272348.o4RNmgWh014243@hugeraid.jetcafe.org> <20100604153210.GA8522@amaretto> <4C093EB5.3060406@cs.rice.edu> <201006041453.36467.jhb@freebsd.org> In-Reply-To: <201006041453.36467.jhb@freebsd.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Matthew D Fleming , Clifton Royston , alc@freebsd.org, Garrett Cooper , freebsd-stable@freebsd.org, Jeremy Chadwick Subject: Re: Locking a file backed mdconfig into memory X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 04 Jun 2010 20:51:48 -0000 On 6/4/2010 1:53 PM, John Baldwin wrote: > On Friday 04 June 2010 1:58:13 pm Alan Cox wrote: > >> Matthew D Fleming wrote: >> >>> On Fri, Jun 04, 2010 at 08:20:49AM -0400, John Baldwin wrote: >>> >>> >>>> Hmmm, I would just try increasing NKPT then. You might have to poke >>>> around in sys/amd64 to see what the default size is and how to tune >>>> it. >>>> >>>> >>> When Isilon did the stable/7 merge and amd64 default NKPT changed from >>> 240 to 32 amd64 started having weird pmap issues during boot. At panic >>> time the stack wasn't very useful, and I didn't finish debugging the >>> issue since eventually I just had to get something working. We just >>> reverted NKPT to 240 and it worked for us. I didn't see an anything in >>> optsions.amd64 so I hard-coded it in amd64/include/pmap.h. >>> >>> Supposedly amd64 can deal with a small NKPT and grow dynamically, but it >>> didn't seem to work for us. :-( Perhaps when we do the next merge >>> project I'll have a few days to devote to debugging the root cause. >>> >>> >> NKPT controls the number of page table pages that are initially >> allocated at the bottom of the top 2GB of the kernel address space. >> However, the vast majority of the kernel address space, 510GB in FreeBSD >> >=7.3, is below these page table pages. The page table pages for this >> region are dynamically allocated as needed. >> >> If you're booting a kernel and modules greater than 64GB in size, then I >> can certainly see why you would need to increase NKPT. >> > 64GB seems like a lot of address space, I would not expect that to be > completely used by kernel and modules. I think earlier in the thread someone > said they had problems with a "mere" 295MB mfsroot. > > Oops. I meant to say 64MB. :-) >> John, is there some way to know at boot time how big the kernel and >> modules were? Then, we could probably eliminate NKPT. >> > I think the loader knows, so it could pass that info to the kernel. > >