Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756617AbXFUQqa (ORCPT ); Thu, 21 Jun 2007 12:46:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753975AbXFUQqT (ORCPT ); Thu, 21 Jun 2007 12:46:19 -0400 Received: from mx1.redhat.com ([66.187.233.31]:60684 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751396AbXFUQqT (ORCPT ); Thu, 21 Jun 2007 12:46:19 -0400 Message-ID: <467AAB04.2070409@redhat.com> Date: Thu, 21 Jun 2007 12:44:52 -0400 From: Chuck Ebbert Organization: Red Hat User-Agent: Thunderbird 1.5.0.12 (X11/20070530) MIME-Version: 1.0 To: Ingo Molnar CC: Linus Torvalds , Jarek Poplawski , Miklos Szeredi , chris@atlee.ca, linux-kernel@vger.kernel.org, tglx@linutronix.de, akpm@linux-foundation.org Subject: Re: [BUG] long freezes on thinkpad t60 References: <20070620093612.GA1626@ff.dom.local> <20070621073031.GA683@elte.hu> <20070621160817.GA22897@elte.hu> In-Reply-To: <20070621160817.GA22897@elte.hu> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1226 Lines: 26 On 06/21/2007 12:08 PM, Ingo Molnar wrote: > yeah - i'm not at all arguing in favor of the BTRL patch i did: i always > liked the 'nicer' inner loop of spinlocks, which could btw also easily > use MONITOR/MWAIT. The "nice" inner loop is necessary or else it would generate huge amounts of bus traffic while spinning. > So it seems the problem was that if a core kept _truly_ modifying a > cacheline via atomics in a high enough frequency, it could artificially > starve the other core. (which would keep waiting for the cacheline to be > released one day, and which kept the first core from ever making any > progress) To me that looks like a real problem on the hardware side - > shouldnt cacheline ownership be arbitrated a bit better than that? > A while ago I showed that spinlocks were a lot more fair when doing unlock with the xchg instruction on x86. Probably the arbitration is all screwed up because we use a mov instruction, which while atomic is not locked. - 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/