On Wed, Apr 13, 2016 at 05:40:20AM +0200, Mike Galbraith wrote: > On Tue, 2016-04-12 at 22:45 +0100, Matt Fleming wrote: > > On Sat, 09 Apr, at 01:30:34PM, Chris Mason wrote: > > > > > > [ nohz throttling patch ] > > > > > > I tested the nohz throttle two different ways, first with schbench's > > > pipe simulation, it's easily 8% faster with messages bouncing between > > > cpus. > > > > > > In production it's hard to pick a single number because the benchmarks > > > produce latency curves as the workload scales up in RPS. The benefits > > > range from 2-9% depending on the metric. It's a nice win, and I'd love to > > > see it go in. > > > > Do we have any idea what the tradeoff is against power consumption for > > throttling nohz? > > That's measurable with the built in super duper watt meter gizmo > (turbostat). It should be dinky but existent, could be given an off > button for particularly attentive laptop drivers to poke. Servers > drivers are unlikely to care given the performance win.
Our power sensors show its basically a wash during the production benchmark runs. Which makes sense because its really only blinking on/off at very high frequency. -chris
