From mboxrd@z Thu Jan 1 00:00:00 1970 From: Max Kellermann Subject: Re: High load in 2.6.27, NFS / rpcauth_lookup_credcache()? Date: Mon, 27 Oct 2008 10:58:43 +0100 Message-ID: <20081027095843.GA10937@squirrel.roonstrasse.net> References: <20081022091207.GA12996@squirrel.roonstrasse.net> <20081023123628.GA18549@squirrel.roonstrasse.net> <1224773745.7625.4.camel@localhost> <20081024083913.GA15197@squirrel.roonstrasse.net> <1224871763.22672.33.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org To: Trond Myklebust Return-path: Received: from smtp4.netcologne.de ([194.8.194.137]:41670 "EHLO smtp4.netcologne.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751559AbYJ0J6q (ORCPT ); Mon, 27 Oct 2008 05:58:46 -0400 In-Reply-To: <1224871763.22672.33.camel@localhost> Sender: linux-nfs-owner@vger.kernel.org List-ID: On 2008/10/24 20:09, Trond Myklebust wrote: > OK, could you please describe your environment a bit. Do you have lots > of different users logged in at the same time, or do you perhaps use > newgrp or su to switch uid/gids a lot on your processes? > I'm trying to see if there might be a reason for the lookup in the > credcache being such a heavy duty operation in your setup. It's a web server for shared hosting. The web space is mounted via NFSv3 from a NetApp. There is a huge number of web sites on this cluster. All web sites are owned by the same UID, and the web server runs as a different UID (read-only access). Each time a CGI starts, its uid is changed to the one "owner" UID (similar to mod_suexec, but there's only one UID for all customer accounts). Each time a CGI starts, its chroot (pivot_root) is constructed with several bind mounts (in a separate namespace with CLONE_NEWNS). There are no new users or groups being created. There are only 2 UIDs accessing NFS: the webserver (ro) and CGI (rw). Max