From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Mitchell Subject: Re: mmap() and NFS server performance Date: Mon, 16 Dec 2002 08:33:57 -0600 Sender: nfs-admin@lists.sourceforge.net Message-ID: <3DFDE455.1000004@geodev.com> References: <3DFA4C9A.50101@geodev.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Cc: nfs@lists.sourceforge.net Return-path: Received: from gateway2.geodev.com ([64.45.165.170] ident=[T2juuA0aXVR4tjY/ellAZwwHtC0/xFq+]) by sc8-sf-list1.sourceforge.net with esmtp (Exim 3.31-VA-mm2 #1 (Debian)) id 18NwNo-00052n-00 for ; Mon, 16 Dec 2002 06:38:12 -0800 To: Trond Myklebust Errors-To: nfs-admin@lists.sourceforge.net List-Help: List-Post: List-Subscribe: , List-Id: Discussion of NFS under Linux development, interoperability, and testing. List-Unsubscribe: , List-Archive: Trond Myklebust wrote: >>>>>>" " == Matthew Mitchell writes: >>>>> > > > values. These apps were originally written on Solaris with > > Solaris NFS servers assumed to be the data source; the Sun guys > > said that mmap would be much faster than read/write and they > > were correct. However, now that we have a few Linux NFS > > servers, we're seeing the opposite. > > As long as the clients are still Solaris, then the only difference can > be the network, and the server performance. > > Of the 2, the bigger 'generic' troublemaker tends to be the network. > Solaris clients always tend to prefer NFS over TCP since that tends to > be more reliable on poor networks than does UDP. Unfortunately, NFS > over TCP on the server side is a fairly recent addition to Linux: it > only just made it into the stable release 2 weeks ago (when 2.4.20 was > released). To the best of my knowledge, none of the RedHat kernels > support it yet. For some reason it had not occurred to me that the NFS server on the Linux box might be using UDP instead of TCP; I had it in my head somehow that it would use TCP. Obviously it wasn't. Now, we had noticed slower speeds with UDP before (when Linux clients were using UDP to access the Solaris servers). Could this be causing such a drastic slowdown? I have looked at some network packet streams and I don't think we are having any of the classic UDP problems -- negligible # of retransmits, most packets arrive in order. The Linux server isn't loaded hardly at all. Three further questions: 1) What would you like to see, tcpdump/snoop wise, to verify this? 2) Could UDP service really be causing this order of magnitude slowdown? 3) Is TCP server code "ready enough" for production use? In our case we don't mind some occasional bugs, but it needs to be able to stay working under reasonable load for a day or so at a time for us to get anything done ("Stale NFS file handle" is a scourge...). Thanks again. -- Matthew Mitchell Systems Programmer/Administrator matthew@geodev.com Geophysical Development Corporation phone 713 782 1234 1 Riverway Suite 2100, Houston, TX 77056 fax 713 782 1829 ------------------------------------------------------- This sf.net email is sponsored by: With Great Power, Comes Great Responsibility Learn to use your power at OSDN's High Performance Computing Channel http://hpc.devchannel.org/ _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs