From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764809AbYHHW1Z (ORCPT ); Fri, 8 Aug 2008 18:27:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1764670AbYHHW04 (ORCPT ); Fri, 8 Aug 2008 18:26:56 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:42889 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763823AbYHHW0z (ORCPT ); Fri, 8 Aug 2008 18:26:55 -0400 Subject: Re: [RFC][PATCH 1/4] checkpoint-restart: general infrastructure From: Dave Hansen To: Arnd Bergmann Cc: containers@lists.linux-foundation.org, Theodore Tso , linux-kernel@vger.kernel.org, Oren Laadan In-Reply-To: <200808090013.41999.arnd@arndb.de> References: <20080807224033.FFB3A2C1@kernel> <200808081146.54834.arnd@arndb.de> <1218221451.19082.36.camel@nimitz> <200808090013.41999.arnd@arndb.de> Content-Type: text/plain Date: Fri, 08 Aug 2008 15:26:51 -0700 Message-Id: <1218234411.19082.58.camel@nimitz> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2008-08-09 at 00:13 +0200, Arnd Bergmann wrote: > > I have to wonder if this is just a symptom of us trying to do this the > > wrong way. We're trying to talk the kernel into writing internal gunk > > into a FD. You're right, it is like a splice where one end of the pipe > > is in the kernel. > > > > Any thoughts on a better way to do this? > > Maybe you can invert the logic and let the new syscalls create a file > descriptor, and then have user space read or splice the checkpoint > data from it, and restore it by writing to the file descriptor. > It's probably easy to do using anon_inode_getfd() and would solve this > problem, but at the same time make checkpointing the current thread > hard if not impossible. Yeah, it does seem kinda backwards. But, instead of even having to worry about the anon_inode stuff, why don't we just put it in a fs like everything else? checkpointfs! I'm also really not convinced that putting the entire checkpoint in one glob is really the solution, either. I mean, is system call overhead really a problem here? -- Dave