On Thu, Mar 22 2007, William Cohen wrote: > Hi all, > > I was trying to make sense of the data that I collected earlier with the > idle1.stp probe. It displayed the percentage of time spent in halted mode, > which the highest I saw on an idle machine was 17 percentage. This seemed > rather low for a machine that was doing nothing, so I took a closer look at > what was going on the idle machine. All this work is based on kernel built > from dilinger's: > > kernel-2.6.21-20070312.1.olpc.3eca75102a57502.src.rpm > > I ran an experiment where the machine state idle for 10 seconds with the > systemtap script running. I also compared the number of interrupts before > and after the experiment. There is about 150 interrupts per second from the > mfgpt timer. I thought with the tickless kernel that this would be a lot > lower. > Below is the data from the experiment. I tried booting the machine in > runlevel three and got the same results, about 150 interrupts per second. > Why so many timer interrupts for tickless kernel?
The tickless kernel just _enables_ low number of interrupts per second, it'll still wakeup everytime something is scheduled to run. So you probably want to look into _why_ th timer interrupts happen so often - who is the user of them? I see ~70 interrupts/sec here with an idle machine in X, FWIW. -- Jens Axboe _______________________________________________ Devel mailing list [email protected] http://mailman.laptop.org/mailman/listinfo/devel
