Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754085Ab2EaUlf (ORCPT ); Thu, 31 May 2012 16:41:35 -0400 Received: from merlin.infradead.org ([205.233.59.134]:41440 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751491Ab2EaUld convert rfc822-to-8bit (ORCPT ); Thu, 31 May 2012 16:41:33 -0400 Message-ID: <1338496857.28384.124.camel@twins> Subject: Re: [PATCH 1/5] ftrace: Synchronize variable setting with breakpoints From: Peter Zijlstra To: Steven Rostedt Cc: Mathieu Desnoyers , linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Frederic Weisbecker , Masami Hiramatsu , "H. Peter Anvin" , Dave Jones , Andi Kleen , acme Date: Thu, 31 May 2012 22:40:57 +0200 In-Reply-To: <1338496676.13348.430.camel@gandalf.stny.rr.com> References: <20120531012829.160060586@goodmis.org> <20120531020440.476352979@goodmis.org> <1338462398.28384.52.camel@twins> <1338473302.13348.336.camel@gandalf.stny.rr.com> <1338486029.28384.93.camel@twins> <1338486820.13348.366.camel@gandalf.stny.rr.com> <1338487413.28384.103.camel@twins> <1338490218.13348.379.camel@gandalf.stny.rr.com> <1338491176.28384.114.camel@twins> <20120531195529.GA22976@Krystal> <1338495006.13348.418.camel@gandalf.stny.rr.com> <1338495969.28384.119.camel@twins> <1338496676.13348.430.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 926 Lines: 42 On Thu, 2012-05-31 at 16:37 -0400, Steven Rostedt wrote: > On Thu, 2012-05-31 at 22:26 +0200, Peter Zijlstra wrote: > > > Right, but when you loose stop-machine you could simply do 30k > > kmap_atomic/kunmap_atomic's consecutively since you're not holding > > anybody up. > > It requires 3 IPIs per update too. Thus that's 90,000 IPIs you are > blasting^Wsending to all CPUs. Uhm, no. for_each() { kmap_atomic() frob int3 kunmap_atomic(); } sync-ipi-broadcast(); for_each() { kmap_atomic(); frob tail kunmap_atomic(); } sync-ipi-broadcast(); for_each() { kmap_atomic(); frob head kunmap_atomic(); }; sync-ipi-broadcast(); How is that sending 90k ipis? -- 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/