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 12:12:56 +0200 Message-ID: <20130801101256.GM3008@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]:33293 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753784Ab3HAKNW (ORCPT ); Thu, 1 Aug 2013 06:13:22 -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 >From what I know big systems are usually build with power-of-two factors. Although I suppose with a ring fabric you could have an arbitrary number of nodes. Anyway, I've heard SGI talk about 4K cpu systems, 8K cpu systems and 16K cpu systems, I've not heard them talk about 16K-n systems. Also, as in other parts of the reply I send, this limitation seems completely unnecessary. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from merlin.infradead.org ([205.233.59.134]:33293 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753784Ab3HAKNW (ORCPT ); Thu, 1 Aug 2013 06:13:22 -0400 Date: Thu, 1 Aug 2013 12:12:56 +0200 From: Peter Zijlstra Subject: Re: [PATCH RFC 1/2] qspinlock: Introducing a 4-byte queue spinlock implementation Message-ID: <20130801101256.GM3008@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: <20130801101256.AtfefL04uGrzCTNAsdUtRNZy2rd-eV75v2ClHCA0Ifw@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 >From what I know big systems are usually build with power-of-two factors. Although I suppose with a ring fabric you could have an arbitrary number of nodes. Anyway, I've heard SGI talk about 4K cpu systems, 8K cpu systems and 16K cpu systems, I've not heard them talk about 16K-n systems. Also, as in other parts of the reply I send, this limitation seems completely unnecessary.