From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTP id ACB49927 for ; Thu, 8 May 2014 14:24:03 +0000 (UTC) Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 6037F201A1 for ; Thu, 8 May 2014 14:24:03 +0000 (UTC) From: "Iyer, Sundar" To: Preeti U Murthy , Peter Zijlstra , "Rafael J. Wysocki" Date: Thu, 8 May 2014 14:23:58 +0000 Message-ID: <2FABAEF0D3DCAF4F9C9628D6E2F9684533B4DABB@BGSMSX102.gar.corp.intel.com> References: <2FABAEF0D3DCAF4F9C9628D6E2F9684533B4C781@BGSMSX102.gar.corp.intel.com> <536B477B.2030800@linux.vnet.ibm.com> In-Reply-To: <536B477B.2030800@linux.vnet.ibm.com> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "Brown, Len" , Daniel Lezcano , Ingo Molnar , "ksummit-discuss@lists.linuxfoundation.org" Subject: Re: [Ksummit-discuss] [TECH(CORE?) TOPIC] Energy conservation bias interfaces List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > -----Original Message----- > From: Preeti U Murthy [mailto:preeti@linux.vnet.ibm.com] > Sent: Thursday, May 8, 2014 2:30 PM > To: Iyer, Sundar; Peter Zijlstra; Rafael J. Wysocki > Cc: Brown, Len; Daniel Lezcano; Ingo Molnar; ksummit- > True that 'race to halt' also ends up saving energy. But when the kernel = goes > conservative on energy, the scheduler would look at racing to idle *withi= n a > power domain* as much as possible. Only if the load crosses a certain > threshold would it spread across to other power domains. I think Rafael mentioned in an another thread about shared supplies and res= ources. In such a case, the race-to-idle within a power domain may actually negate = the overall platform savings. And to confirm, you are referring to generic power domains beyond the CPU r= ight? > These are general heuristics. These simple heuristics must work out for m= ost > platforms but may not work for all. If it works for majority of the cases= then > I believe we can safely call it a success. And which is why I mentioned that this is heavily platform dependent. This = is=20 completely dependent on how the rest of the system power management works. Cheers!