From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754799AbXKMKX1 (ORCPT ); Tue, 13 Nov 2007 05:23:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751731AbXKMKXT (ORCPT ); Tue, 13 Nov 2007 05:23:19 -0500 Received: from gate.crashing.org ([63.228.1.57]:49435 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328AbXKMKXS (ORCPT ); Tue, 13 Nov 2007 05:23:18 -0500 Subject: Re: [PATCH, RFC] improved hacks to allow -rt to run kernbench on POWER From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Peter Zijlstra Cc: paulmck@linux.vnet.ibm.com, Steven Rostedt , linux-kernel@vger.kernel.org, tony@bakeyournoodle.com, paulus@samba.org, dino@in.ibm.com, tytso@us.ibm.com, dvhltc@us.ibm.com, niv@us.ibm.com, antonb@us.ibm.com, Ingo Molnar In-Reply-To: <1194945032.6983.11.camel@twins> References: <20071109181028.GA26800@linux.vnet.ibm.com> <1194641524.21340.14.camel@pasglop> <20071109220717.GJ8826@linux.vnet.ibm.com> <1194753541.21340.26.camel@pasglop> <1194814125.6510.14.camel@pasglop> <20071112191526.GC11113@linux.vnet.ibm.com> <1194901925.18185.65.camel@pasglop> <1194945032.6983.11.camel@twins> Content-Type: text/plain Date: Tue, 13 Nov 2007 20:43:46 +1100 Message-Id: <1194947026.18185.95.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.12.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2007-11-13 at 10:10 +0100, Peter Zijlstra wrote: > > Correct, -rt can't allocate -anything- when preemption if off. That is > the cost for having the allocators itself preemptable. > > Even radix_tree_preload() will not work as its functionality was based > on preempt disable to limit access to a global (per cpu) object > reserve. > But maybe something similar could be done with a local reserve by > using > struct radix_tree_context to pass it along. > > I'll see if I can come up with anything like that, that is, if that > would suffice? For that specific problem, as long as the radix tree can be made to work while non-preemptible, I'm fine :-) I'm still worried by other cases where things expect GFP_ATOMIC to work at any time. Ben.