From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul Smith" Subject: Re: NFS client write performance issue ... thoughts? Date: 12 Jan 2004 12:30:24 -0500 Sender: nfs-admin@lists.sourceforge.net Message-ID: References: <75587E33AC778145AACCE1601EEABF420D49B2@kda-beexc-02.kda.kongsberg.com> Reply-To: "Paul Smith" Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Return-path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.12] helo=sc8-sf-mx2.sourceforge.net) by sc8-sf-list2.sourceforge.net with esmtp (Exim 4.24) id 1Ag5tc-0003Ei-Nd for nfs@lists.sourceforge.net; Mon, 12 Jan 2004 09:30:36 -0800 Received: from zrtps0kp.nortelnetworks.com ([47.140.192.56]) by sc8-sf-mx2.sourceforge.net with esmtp (Exim 4.30) id 1Ag5tc-0001DB-8w for nfs@lists.sourceforge.net; Mon, 12 Jan 2004 09:30:36 -0800 To: "Mikkelborg, Kjetil" In-Reply-To: <75587E33AC778145AACCE1601EEABF420D49B2@kda-beexc-02.kda.kongsberg.com> Errors-To: nfs-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: Discussion of NFS under Linux development, interoperability, and testing. List-Post: List-Help: List-Subscribe: , List-Archive: %% "Mikkelborg, Kjetil" writes: Hi; can you please use normal quoting when replying to email? If you just include the entire original then type some comments in the middle it's very difficult to find the comments you made. Thanks! pds> ClearCase implements its own virtual filesystem type, and so is pds> heavily tied to specific kernels (the kernel module is not open pds> source of course :( ). We basically can move to any kernel that pds> has been released as part of an official Red Hat release (say, pds> 2.4.20-8 from RH9 would work), but no other kernels can be used pds> (the ClearCase kernel module has checks on the sizes of various pds> kernel structures and won't load if they're not what it thinks pds> they should be--and since it's a filesystem it cares deeply about pds> structures that have tended to change a lot. It won't even work pds> with vanilla kernel.org kernels of the same version.) mk> Actually It does not look like clearcase is checking for an exact mk> kernel version, it just depends on redhat hacks in the kernel (I mk> have no clue to which). I didn't say it was checking for an exact kernel version. I said it checks the sizes of various kernel structures. This is done dynamically when the kernel module is loaded. The way it works is this: the MVFS filesystem loadable module comes in two parts: a precompiled part which you don't get the source to, and a .c file which is a "wrapper". The wrapper is recompiled against your current kernel, headers, etc. then the two are linked together to form the real mvfs.o module. The wrapper provides a buffer against some kinds of changes to the kernel. But, the wrapper also examines about 30 different kernel data structures and compares their sizes in your kernel against the ones expected in the prebuilt .o file. If they're different then the module won't load. Some of these are pretty static, like "struct timeval", but some are much more dynamic, like "struct file", etc. For some structures they care about the size of the whole structure, for some they care about the offset into the structure of a given field. mk> But taking a 2.4.20-XX redhat kernel, and building it from SRPM mk> actually work. Furthermore, since you have the kernel in source mk> when building it from SRPM, I never bother to build from the SRPM. It's much more straightforward to build from the kernel-source RPM. YMMV of course. mk> you can add as many patches as you want, as long as these patches mk> does not screw with the same stuff clearcase mvfs relies on. I mk> managed to do some heavy modifying of a rh9 kernel SRPM, patch it mk> up to what level I needed + include support for diskless boot. Yes; as long as you don't mess with the structures ClearCase cares about, you win. You can find the exact structures in question in the STRUCT_CHECK_INIT macro in the mvfs_param.h file in the ClearCase distribution directory. -- ------------------------------------------------------------------------------- Paul D. Smith HASMAT--HA Software Mthds & Tools "Please remain calm...I may be mad, but I am a professional." --Mad Scientist ------------------------------------------------------------------------------- These are my opinions---Nortel Networks takes no responsibility for them. ------------------------------------------------------- This SF.net email is sponsored by: Perforce Software. Perforce is the Fast Software Configuration Management System offering advanced branching capabilities and atomic changes on 50+ platforms. Free Eval! http://www.perforce.com/perforce/loadprog.html _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs