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Date: Thu, 13 Dec 2012 11:07:43 +0800 From: Alex Shi <alex.shi@...el.com> To: Borislav Petkov <bp@...en8.de>, Arjan van de Ven <arjan@...ux.intel.com>, Alex Shi <lkml.alex@...il.com>, rob@...dley.net, mingo@...hat.com, peterz@...radead.org, gregkh@...uxfoundation.org, andre.przywara@....com, rjw@...k.pl, paul.gortmaker@...driver.com, akpm@...ux-foundation.org, paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org, pjt@...gle.com, vincent.guittot@...aro.org, Preeti U Murthy <preeti@...ux.vnet.ibm.com> Subject: Re: [PATCH 0/18] sched: simplified fork, enable load average into LB and power awareness scheduling >> now, on the other hand, if you have two threads of a process that >> share a bunch of data structures, and you'd spread these over 2 >> sockets, you end up bouncing data between the two sockets a lot, >> running inefficient --> bad for power. > > Yeah, that should be addressed by the NUMA patches people are working on > right now. Yes, as to balance/powersaving policy, we can tight pack tasks firstly, then NUMA balancing will make memory follow us. BTW, NUMA balancing is more related with page in memory. not LLC. > >> having said all this, if you have to tasks that don't have such >> cache effects, the most efficient way of running things will be on 2 >> hyperthreading halves... it's very hard to beat the power efficiency >> of that. But this assumes the tasks don't compete with resources much >> on the HT level, and achieve good scaling. and this still has to >> compete with "race to halt", because if you're done quicker, you can >> put the memory in self refresh quicker. > > Right, how are we addressing the breakeven in that case? AFAIK, we > do schedule them now on two different cores (not HT threads, i.e. no > resource sharing besides L2) so that we get done faster, i.e. race to that's balance policy for. :) > idle in the performance case. And in the powersavings' case we leave > them as tightly packed as possible. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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