From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754586AbYIXKUO (ORCPT ); Wed, 24 Sep 2008 06:20:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751919AbYIXKUA (ORCPT ); Wed, 24 Sep 2008 06:20:00 -0400 Received: from gate.crashing.org ([63.228.1.57]:38417 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751467AbYIXKT7 (ORCPT ); Wed, 24 Sep 2008 06:19:59 -0400 Subject: Re: [PATCH HACK] powerpc: quick hack to get a functional eHEA with hardirq preemption From: Benjamin Herrenschmidt Reply-To: benh@kernel.crashing.org To: Milton Miller Cc: Sebastien Dugue , Jan-Bernd Themann , Christoph Raisch , Paul Mackerras , linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org In-Reply-To: <200809240958.m8O9wM7k010996@sullivan.realtime.net> References: <200809231743.23828.ossthema@de.ibm.com> , <20080915100406.342e027a@bull.net> <200809240958.m8O9wM7k010996@sullivan.realtime.net> Content-Type: text/plain Date: Wed, 24 Sep 2008 20:17:47 +1000 Message-Id: <1222251467.8277.73.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2008-09-24 at 04:58 -0500, Milton Miller wrote: > The per-interrupt mask and unmask calls have to go through RTAS, a > single-threaded global context, which in addition to increasing > path length will really limit scalability. The interrupt controller > poll and reject facilities are accessed through hypervisor calls > which are comparable to a fast syscall, and parallel to all cpus. Note also that the XICS code thus assumes, iirc, as does the cell IIC code, that eoi is called on the -same- cpu that fetched the interrupt initially. That assumption can be broken with IRQ threads no ? Ben.