From owner-freebsd-hackers@FreeBSD.ORG Tue Feb 15 12:51:50 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 54C1F106566B for ; Tue, 15 Feb 2011 12:51:50 +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 251E38FC19 for ; Tue, 15 Feb 2011 12:51:50 +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 CC41A46B09; Tue, 15 Feb 2011 07:51:49 -0500 (EST) Received: from jhbbsd.localnet (unknown [209.249.190.10]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id EC22F8A02A; Tue, 15 Feb 2011 07:51:48 -0500 (EST) From: John Baldwin To: "beezarliu" Date: Tue, 15 Feb 2011 07:50:31 -0500 User-Agent: KMail/1.13.5 (FreeBSD/7.4-CBSD-20110107; KDE/4.4.5; amd64; ; ) References: <201102141718415933573@yahoo.com.cn> <201102140939.17486.jhb@freebsd.org> <201102151112522035530@yahoo.com.cn> In-Reply-To: <201102151112522035530@yahoo.com.cn> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201102150750.31797.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6 (bigwig.baldwin.cx); Tue, 15 Feb 2011 07:51:49 -0500 (EST) X-Virus-Scanned: clamav-milter 0.96.3 at bigwig.baldwin.cx X-Virus-Status: Clean X-Spam-Status: No, score=0.5 required=4.2 tests=BAYES_00,MAY_BE_FORGED, RDNS_DYNAMIC autolearn=no version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on bigwig.baldwin.cx Cc: "freebsd-hackers@freebsd.org" Subject: Re: map share memory to kernel space 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: Tue, 15 Feb 2011 12:51:50 -0000 On Monday, February 14, 2011 10:12:59 pm beezarliu wrote: > On 2011-02-14 22:56:28, John Baldwin wrote: > >On Monday, February 14, 2011 4:18:50 am beezarliu wrote: > >> Hackers, > >> > >> I want to access a userland share memory in a kernel thread. > >> So I tried to map the share memory to the kernel space. > >> The basic idea is to map the shm_object into kernel_map > >> when the share memory is created. > >> > >> Using the following patch, I found the vm_object in kernel_map, > >> and the vm_object in the address space of userland process are the same. > >> But their content in the kernel and userland address mapped are different. > >> > >> It's very strang since they are exactly the same vm_object. > >> Do I miss something, please help. > > > >Hmm, this is a bit of code I use for something similar to map a VM object into > >the kernel. It does not use vm_page_grab() directly though: > > > Initially, I wanted to allocate all the pages needed when the share memory is created, > in order to reduce page fault at the time it's used. > This seems to be an extra step. :( > > John, thank you very much! I think vm_map_wire() will find pages for you when it wires the object. -- John Baldwin