Messages in this thread | | | Date | Mon, 26 Nov 2007 21:38:47 -0800 | From | Arjan van de Ven <> | Subject | Re: Dynticks Causing High Context Switch Rate in ksoftirqd |
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On Mon, 26 Nov 2007 22:36:17 -0600 Robert Hancock <hancockr@shaw.ca> wrote:
> bdupree@techfinesse.com wrote: > > Question: Why is ksoftirqd eating about 5 to 10 percent of my CPU > > on an idle system? The problem occurs if I config the kernel with > > tickless support (i.e. CONFIG_TICK_ONESHOT=y). (Thanks to > > "oprofile" for putting me onto this.) > > > > I have noted this same problem on kernel versions: 2.6.23.1, > > 2.6.23.8 and 2.6.23.9 > > > > ************************************************************************** > > *** Output from "vmstat -n 1 10" -- Note very high context switch > > rate *** *** This is on a idle > > machine! *** > > ************************************************************************** > > > > procs -----------memory---------- ---swap-- -----io---- --system-- > > ----cpu---- > > r b swpd free buff cache si so bi bo in cs > > us sy id wa > > 0 0 0 1925556 4768 116104 0 0 124 2 6 > > 7538 1 2 96 1 > > 0 0 0 1925556 4768 116104 0 0 0 0 2 > > 147329 0 1 99 0 > > What did oprofile show? It should be able to narrow down what > function(s) are responsible for the CPU usage.. >
or better, what does powertop version 1.9 show? that tends to show tickless wakeup artifacts quite nicely
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