Thanks for your insights Viresh & Dirk. I really appreciate it. I read from the net that the p-state (Voltage/Frequency) pairs in Intel processors(e.g Nehalem) cannot be set for individual cores (http://web.archive.org/web/20130527001342/http://people.cs.pitt.edu/~kirk/cs3150spring2010/ShiminChen.pptx). As Dirk pointed out, each core may request a p-state but ultimately all the whole processor's p-state is set to the minimum of the requested p-states. But in my Core2Duo processor, I see that two cores are in different frequencies(p-state) and it did not fit into the explanation above :-(. I think I am missing something. Regards, karthik On Sun, May 26, 2013 at 3:01 AM, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: > On 26 May 2013 05:30, karthik vm <meetvm@xxxxxxxxx> wrote: >> Thanks for your insights Viresh. I really appreciate it!! >> >> Basically I wanted to know the DVFS granularity of a multi-core chip. >> i.e I want to know whether every core can separately increase or >> decrease its frequency or all the cores increase or decrease >> simultaneously. I think cpufreq-info command's output "CPUs which need >> to have their frequency coordinated by software" gives the answer. For >> my core2duo processor it says either core 0 or core 1. Hence frequency >> of each of my cores can be changed individually. Experimental results >> also supports it. Please correct me if there is any fallacy in my >> inference. > > Whether cores can have separate control of clks or not is decided by > hardware implementation. On ARM normally all cores within a cluster > have common control of clk lines.. On Intel, I am not sure. > > Now, the hardware can have interesting capabilities where they can > manage separate clk lines themselves and software doesn't need to > do anything special for them. And so that's what Dirk pointed out > earlier. > > Your observation looks correct though. -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
