Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261966AbVE1CDm (ORCPT ); Fri, 27 May 2005 22:03:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262095AbVE1CDm (ORCPT ); Fri, 27 May 2005 22:03:42 -0400 Received: from ms-smtp-03.nyroc.rr.com ([24.24.2.57]:63470 "EHLO ms-smtp-03.nyroc.rr.com") by vger.kernel.org with ESMTP id S261966AbVE1CC7 (ORCPT ); Fri, 27 May 2005 22:02:59 -0400 Subject: Re: spinaphore conceptual draft (was discussion of RT patch) From: Steven Rostedt To: David Nicol Cc: linux-kernel@vger.kernel.org, john cooper In-Reply-To: <934f64a205052715315c21d722@mail.gmail.com> References: <934f64a205052715315c21d722@mail.gmail.com> Content-Type: text/plain Organization: Kihon Technologies Date: Fri, 27 May 2005 22:02:45 -0400 Message-Id: <1117245765.6477.34.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 927 Lines: 21 One thing you are forgetting is that we are not just talking about the latencies of contention. We are talking about the latency of a high priority process when it wakes up to the time it runs. Most of the time a spin lock stops preemption, either with (CONFIG_PREEMPT) preempt_disable or simple turning off interrupts. With Ingo's mutexes, the places with spin_locks are now preemptable. So there is probably lots of times that it would be better to just spin on contention, but that's not what Ingo's spin_locks are saving us. It's to keep most of the kernel preemptable. The priority inheritance of spin_locks is simply there to protect from priority inversion. -- Steve - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/