Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751793AbaANR7Y (ORCPT ); Tue, 14 Jan 2014 12:59:24 -0500 Received: from terminus.zytor.com ([198.137.202.10]:54223 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751500AbaANR7S (ORCPT ); Tue, 14 Jan 2014 12:59:18 -0500 Message-ID: <52D57AC2.3090109@zytor.com> Date: Tue, 14 Jan 2014 09:58:26 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Peter Zijlstra , "Waskiewicz Jr, Peter P" CC: Tejun Heo , Thomas Gleixner , Ingo Molnar , Li Zefan , "containers@lists.linux-foundation.org" , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 0/4] x86: Add Cache QoS Monitoring (CQM) support References: <20140106180636.GG30183@twins.programming.kicks-ass.net> <1389039035.32504.35.camel@ppwaskie-mobl.amr.corp.intel.com> <20140106212623.GH30183@twins.programming.kicks-ass.net> <1389044899.32504.43.camel@ppwaskie-mobl.amr.corp.intel.com> <20140106221251.GJ30183@twins.programming.kicks-ass.net> <1389048315.32504.57.camel@ppwaskie-mobl.amr.corp.intel.com> <20140107083440.GL30183@twins.programming.kicks-ass.net> <1389107743.32504.69.camel@ppwaskie-mobl.amr.corp.intel.com> <20140107211229.GF2480@laptop.programming.kicks-ass.net> <1389380100.32504.172.camel@ppwaskie-mobl.amr.corp.intel.com> <20140113075528.GR7572@laptop.programming.kicks-ass.net> In-Reply-To: <20140113075528.GR7572@laptop.programming.kicks-ass.net> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/12/2014 11:55 PM, Peter Zijlstra wrote: > > The problem is, since there's a limited number of RMIDs we have to > rotate at some point, but since changing RMIDs is nondeterministic we > can't. > This is fundamentally the crux here. RMIDs are quite expensive for the hardware to implement, so they are limited - but recycling them is *very* expensive because you literally have to touch every line in the cache. -hpa -- 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/