Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753712Ab0A2Slr (ORCPT ); Fri, 29 Jan 2010 13:41:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753636Ab0A2Slq (ORCPT ); Fri, 29 Jan 2010 13:41:46 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:33627 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751630Ab0A2Slq (ORCPT ); Fri, 29 Jan 2010 13:41:46 -0500 Message-ID: <4B632BE2.9020106@austin.ibm.com> Date: Fri, 29 Jan 2010 12:41:38 -0600 From: Joel Schopp User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Benjamin Herrenschmidt CC: Peter Zijlstra , ego@in.ibm.com, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCHv3 2/2] powerpc: implement arch_scale_smt_power for Power7 References: <1264017638.5717.121.camel@jschopp-laptop> <1264017847.5717.132.camel@jschopp-laptop> <1264548495.12239.56.camel@jschopp-laptop> <1264720855.9660.22.camel@jschopp-laptop> <1264721088.10385.1.camel@jschopp-laptop> <1264728185.20211.34.camel@pasglop> In-Reply-To: <1264728185.20211.34.camel@pasglop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1666 Lines: 38 Benjamin Herrenschmidt wrote: > On Thu, 2010-01-28 at 17:24 -0600, Joel Schopp wrote: > >> On Power7 processors running in SMT4 mode with 2, 3, or 4 idle threads >> there is performance benefit to idling the higher numbered threads in >> the core. >> >> This patch implements arch_scale_smt_power to dynamically update smt >> thread power in these idle cases in order to prefer threads 0,1 over >> threads 2,3 within a core. >> > > Almost there :-) Joel, Peter, can you help me figure something out tho ? > > On machine that don't have SMT, I would like to avoid calling > arch_scale_smt_power() at all if possible (in addition to not compiling > it in if SMT is not enabled in .config). > > Now, I must say I'm utterly confused by how the domains are setup and I > haven't quite managed to sort it out... it looks to me that > SD_SHARE_CPUPOWER is always going to be set on all CPUs when the config > option is set (though each CPU will have its own domain) or am I > misguided ? IE. Is there any sense in having at least a fast exit path > out of arch_scale_smt_power() for non-SMT CPUs ? > > Joel, can you look at compiling it out when SMT is not set ? We don't > want to bloat SMP kernels for 32-bit non-SMT embedded platforms. > I can wrap the powerpc definition of arch_scale_smt in an #ifdef, if it's not there the scheduler uses the default, which is the same as it uses if SMT isn't compiled. -- 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/