Return-Path: Received: from mail-out2.uio.no ([129.240.10.58]:37311 "EHLO mail-out2.uio.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932123AbZICUta (ORCPT ); Thu, 3 Sep 2009 16:49:30 -0400 Subject: Re: VM issue causing high CPU loads From: Trond Myklebust To: Simon Kirby Cc: Yohan , Andrew Morton , linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, Neil Brown , "J. Bruce Fields" , mikevs@xs4all.net In-Reply-To: <20090903200550.GB5257@hostway.ca> References: <4A92A25A.4050608@yohan.staff.proxad.net> <20090824162155.ce323f08.akpm@linux-foundation.org> <4A96463E.5080002@corp.free.fr> <4A9C34F8.2010307@corp.free.fr> <20090902170642.f4381c1d.akpm@linux-foundation.org> <1251982884.18338.9.camel@heimdal.trondhjem.org> <4A9FC719.9020104@corp.free.fr> <1251986526.18338.29.camel@heimdal.trondhjem.org> <20090903200550.GB5257@hostway.ca> Content-Type: text/plain Date: Thu, 03 Sep 2009 16:49:25 -0400 Message-Id: <1252010965.18338.63.camel@heimdal.trondhjem.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Thu, 2009-09-03 at 13:05 -0700, Simon Kirby wrote: > On Thu, Sep 03, 2009 at 10:02:06AM -0400, Trond Myklebust wrote: > > > OK, so 16 hash buckets are likely to be filled with ~10^6 entries each. > > I can see that might be a performance issue... > > We have a similar setup with millions of UIDs over NFS (currently NFSv3). > I _wish_ there were a way to use NFSv4 without having to use name-mapped > UIDs and GIDs, since our user and group names come from MySQL anyway, and > are guaranteed to be consistent across machines. That's a separate issue. I'm working on increasing the idmapper scalability, however another project is currently taking up most of my time. I can't guarantee that the revised idmapper code will be finished in time to allow for inclusion in 2.6.32. > Why on earth does NFSv4 force the use of names? NFSv4 aspires to be an internet-wide protocol, and so you cannot use uids/gids: they just aren't guaranteed to represent a unique user outside your local LDAP/NIS or /etc/passwd domain. Furthermore, uids and gids are a posix construct. They simply don't work in environments where you may have lots of non-posix systems. Trond