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Date: Mon, 9 Nov 2015 16:21:20 -0800 From: Jacob Pan <jacob.jun.pan@...ux.intel.com> To: Peter Zijlstra <peterz@...radead.org>, LKML <linux-kernel@...r.kernel.org> Cc: Rafael Wysocki <rafael.j.wysocki@...el.com>, Len Brown <len.brown@...el.com>, Andi Kleen <andi.kleen@...el.com>, Thomas Gleixner <tglx@...utronix.de>, Paul Turner <pjt@...gle.com>, Tim Chen <tim.c.chen@...ux.intel.com>, Dietmar Eggemann <dietmar.eggemann@....com>, Eduardo Valentin <edubezval@...il.com>, Punit Agrawal <punit.agrawal@....com>, Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Jacob Pan <jacob.jun.pan@...ux.intel.com> Subject: [RFC PATCH v2 0/3] CFS idle injection Hi Peter and all, Changes since initial RFC: - integrated Peter's patch to optimize hot path - check softirq, allow softirqd - changed tracing function to include string message Kconfig is not changed, wanted to hear more feedback. Whether this should be a CONFIG option since we already optimized for the hot path. Intro: A while ago, we had discussion about how powerclamp is broken in the sense of turning off idle ticks in the forced idle period. https://lkml.org/lkml/2014/12/18/369 It was suggested to replace the current kthread play idle loop with a timer based runqueue throttling scheme. I finally got around to implement this and code is much simpler. I also have good test results in terms of efficiency, scalability, etc. http://events.linuxfoundation.org/sites/events/files/slides/LinuxCon_Japan_2015_idle_injection1_0.pdf slide #18+ shows the data on client and server. I have two choices for this code: 1) be part of existing powerclamp driver but require exporting some sched APIs. 2) be part of sched since the genernal rule applies when it comes down to sycnhronized idle time for best power savings. The patches below are for #2. There is a known problem with LOW RES timer mode that I am working on. But I am hoping to get review earlier. We are entering a very power limited environment on client side, frequency scaling can only be efficient at certain range. e.g. on SKL, upto ~900MHz, anything below, it is increasingly more efficient to do C-states insertion if coordinated. Looking forward, there are use case beyond thermal/power capping. I think we can consolidate ballanced partial busy workload that are evenly distributed among CPUs. Please let me know what you think. Thanks, Jacob Pan (3): ktime: add a roundup function timer: relax tick stop in idle entry sched: introduce synchronized idle injection include/linux/ktime.h | 10 ++ include/linux/sched.h | 12 ++ include/linux/sched/sysctl.h | 5 + include/trace/events/sched.h | 23 +++ init/Kconfig | 8 + kernel/sched/fair.c | 381 ++++++++++++++++++++++++++++++++++++++++++- kernel/sched/sched.h | 2 +- kernel/sysctl.c | 20 +++ kernel/time/tick-sched.c | 2 +- 9 files changed, 457 insertions(+), 6 deletions(-) -- 1.9.1 -- 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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