From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH RFC 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation Date: Thu, 1 Aug 2013 12:14:24 +0200 Message-ID: <20130801101424.GN3008@twins.programming.kicks-ass.net> References: <1375324631-32868-1-git-send-email-Waiman.Long@hp.com> <1375324631-32868-2-git-send-email-Waiman.Long@hp.com> <20130801094029.GK3008@twins.programming.kicks-ass.net> <51FA3455.1000607@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from merlin.infradead.org ([205.233.59.134]:33335 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751900Ab3HAKOm (ORCPT ); Thu, 1 Aug 2013 06:14:42 -0400 Content-Disposition: inline In-Reply-To: <51FA3455.1000607@linux.vnet.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Raghavendra K T Cc: Waiman Long , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Arnd Bergmann , linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Steven Rostedt , Andrew Morton , Richard Weinberger , Catalin Marinas , Greg Kroah-Hartman , Matt Fleming , Herbert Xu , Akinobu Mita , Rusty Russell , Michel Lespinasse , Andi Kleen , Rik van Riel , "Paul E. McKenney" , Linus Torvalds , George Spelvin , Harvey Harrison On Thu, Aug 01, 2013 at 03:41:33PM +0530, Raghavendra K T wrote: > It is exactly 16k-1 not 15k > That is because CPU_CODE of 1 to 16k represents cpu 0..16k-1 > More specifically: + BUILD_BUG_ON(CONFIG_NR_CPUS >= MAX_CPUS); Our NR_CPUS is very much a power of two. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:33335 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751900Ab3HAKOm (ORCPT ); Thu, 1 Aug 2013 06:14:42 -0400 Date: Thu, 1 Aug 2013 12:14:24 +0200 From: Peter Zijlstra Subject: Re: [PATCH RFC 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation Message-ID: <20130801101424.GN3008@twins.programming.kicks-ass.net> References: <1375324631-32868-1-git-send-email-Waiman.Long@hp.com> <1375324631-32868-2-git-send-email-Waiman.Long@hp.com> <20130801094029.GK3008@twins.programming.kicks-ass.net> <51FA3455.1000607@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51FA3455.1000607@linux.vnet.ibm.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Raghavendra K T Cc: Waiman Long , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Arnd Bergmann , linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Steven Rostedt , Andrew Morton , Richard Weinberger , Catalin Marinas , Greg Kroah-Hartman , Matt Fleming , Herbert Xu , Akinobu Mita , Rusty Russell , Michel Lespinasse , Andi Kleen , Rik van Riel , "Paul E. McKenney" , Linus Torvalds , George Spelvin , Harvey Harrison , "Chandramouleeswaran, Aswin" , "Norton, Scott J" Message-ID: <20130801101424.4_EPcQ3o8bD52l2Gpw64n97ynJDZWGLg7Ny-yHcNlcI@z> On Thu, Aug 01, 2013 at 03:41:33PM +0530, Raghavendra K T wrote: > It is exactly 16k-1 not 15k > That is because CPU_CODE of 1 to 16k represents cpu 0..16k-1 > More specifically: + BUILD_BUG_ON(CONFIG_NR_CPUS >= MAX_CPUS); Our NR_CPUS is very much a power of two.