From owner-freebsd-stable@FreeBSD.ORG Fri Jun 4 20:21:24 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 CEA861065676; Fri, 4 Jun 2010 20:21:24 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 9BD128FC08; Fri, 4 Jun 2010 20:21:24 +0000 (UTC) Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net [66.111.2.69]) by cyrus.watson.org (Postfix) with ESMTPSA id 472A846B51; Fri, 4 Jun 2010 16:21:24 -0400 (EDT) Received: from jhbbsd.localnet (smtp.hudson-trading.com [209.249.190.9]) by bigwig.baldwin.cx (Postfix) with ESMTPA id 2667E8A026; Fri, 4 Jun 2010 16:21:23 -0400 (EDT) From: John Baldwin To: Alan Cox Date: Fri, 4 Jun 2010 14:53:36 -0400 User-Agent: KMail/1.12.1 (FreeBSD/7.3-CBSD-20100217; KDE/4.3.1; amd64; ; ) References: <201005272348.o4RNmgWh014243@hugeraid.jetcafe.org> <20100604153210.GA8522@amaretto> <4C093EB5.3060406@cs.rice.edu> In-Reply-To: <4C093EB5.3060406@cs.rice.edu> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201006041453.36467.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.0.1 (bigwig.baldwin.cx); Fri, 04 Jun 2010 16:21:23 -0400 (EDT) X-Virus-Scanned: clamav-milter 0.95.1 at bigwig.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=-2.5 required=4.2 tests=AWL,BAYES_00 autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on bigwig.baldwin.cx 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 20:21:24 -0000 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. > 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. -- John Baldwin