From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.12] helo=sc8-sf-mx2.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1CnmAf-0003VI-0O for user-mode-linux-devel@lists.sourceforge.net; Sun, 09 Jan 2005 15:08:29 -0800 Received: from dsl092-053-140.phl1.dsl.speakeasy.net ([66.92.53.140] helo=grelber.thyrsus.com) by sc8-sf-mx2.sourceforge.net with esmtp (TLSv1:AES256-SHA:256) (Exim 4.41) id 1CnmAa-0001GM-9u for user-mode-linux-devel@lists.sourceforge.net; Sun, 09 Jan 2005 15:08:28 -0800 From: Rob Landley Subject: Re: [uml-devel] How stable is hostfs (and UML in general)? References: <200501082106.38306.rob@landley.net> <41E0C885.3020608@tuxrocks.com> In-Reply-To: <41E0C885.3020608@tuxrocks.com> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200501091706.58778.rob@landley.net> Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Sun, 9 Jan 2005 17:06:58 -0500 To: Frank Sorenson Cc: user-mode-linux-devel@lists.sourceforge.net On Sunday 09 January 2005 01:00 am, Frank Sorenson wrote: > I may not be able to answer all your questions, but I may be able to > offer a few pointers. > > For the UML kernel version, the stock 2.6.x kernel is getting better, > but still isn't the most stable and reliable kernel. Right now, the > most stable I've found is using 2.6.9 from kernel.org, with the -bb4 > patches from > http://www.user-mode-linux.org/~blaisorblade/patches/guest/uml-2.6.9-bb4/ Hmmm... Cool. Grabbed it, I'll try to look through it tonight to see what's already in 2.6.10 and what isn't... > There are several thing you can do to improve the speed at which the UML > runs. When UML starts, it opens a file in /tmp (or somewhere else if > TMPDIR is set), mmaps it, and uses that as its memory. To speed this > up, make sure that it's located on a tmpfs-mounted filesystem (so it's > real memory). Ah. Definitely a good thing to know, (and non-obvious, and not in any FAQ I've read yet). On the other hand, if I bundle up the firmware linux build process, I'm not really going to be able to control what environment it runs in. (That's kind of the point. I'm developing/testing it on knoppix as a reasonable minimal build environment.) I suppose I could mount tmpfs myself and set TMPDIR, but that assumes the script is being run as root and another benefit of using UML is getting away from the need to do that for chroot and mknod and such... I remember way way back, that there used to be a gross hack people would do to get shared memory (before shm), which was create a file somewhere, have all the processes that needed to share memory open the file, and then delete the file. That signalled the operating system to stop updating the on-disk copy. I wonder if that old hack (deleting the file signalling there's no rush about writing stuff back to the disk anymore, although it's still your backing store) still works? Why does it do this instead of just mallocing stuff, anyway? (Quick and dirty shared memory again?) > fstab: > none /UML/MEMORY tmpfs defaults,size=768M 0 0 > > Starting the UML: > export TMPDIR=/UML/MEMORY > /UML/linux ... > > > Also, with an unpatched host kernel, your UML will run slower. If > possible, patch the host kernel to allow UMLs to run in SKAS mode and > take advantage of some SYSEMU code. These patches are also here: > http://www.user-mode-linux.org/~blaisorblade/patchlist.html or you can > get the 2.6.10 host patch from > http://uml.tuxrocks.com/Patches/host-skas3-2.6.10-v7.patch I know. But once again, I'm tryng to use UML in hopes of being more portable and doing without root access. Patching the kernel defeats the point entirely, I might as well just tell people "you'll need to boot 2.6.10 to build this, and it needs to be run as root". I'm more interested in correctness than performance at the moment. As long as it WORKS, they can leave it running overnight for now... > I don't know much about hostfs, so I can't give any real ideas there. > UML doesn't support TLS yet, so make sure that your UML root_fs doesn't > have a /lib/tls directory. The knoppix host system does, but the build directory I'm giving it doesn't. Hmmm... I wonder what TLS _is_? Internationalization, I suspect. It seems unlikely knoppix would waste space on a second copy of libc for any other reason... > Hope this helps, Yes, actually. Thanks. :) > Frank Rob ------------------------------------------------------- The SF.Net email is sponsored by: Beat the post-holiday blues Get a FREE limited edition SourceForge.net t-shirt from ThinkGeek. It's fun and FREE -- well, almost....http://www.thinkgeek.com/sfshirt _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel