Messages in this thread | | | Date | Mon, 14 Apr 2014 13:47:44 +0200 | From | Peter Zijlstra <> | Subject | Re: [Query]: tick-sched: why don't we stop tick when we are running idle task? |
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On Mon, Apr 14, 2014 at 05:12:08PM +0530, Viresh Kumar wrote: > On 14 April 2014 16:32, Peter Zijlstra <peterz@infradead.org> wrote: > > I'm still not sure _what_ you're trying to solve here. What are you > > doing and why? > > Hi Peter, > > We are working building ARM Networking machines. Networking Data > plane is handled completely at user space. At run time we may fix > any number of CPUs for data plane activities. There will be a single > user space thread per CPU for these data plane packet processing. > Due to timing constraints these cores can't allow any interruption > from kernel. These include interruption from: > > - other tasks: Fixed with cpusets > - timers/hrtimers: Implemented cpuset.quiesce as you suggested: > Waiting for reviews > - workqueues: Probably would be fixed by Frederic's work.
Ok.
> - Tick: Even with NO_HZ_FULL we get a tick every second. This is > what I am trying to address here. Frederic earlier suggested to > offload this accounting to other CPUs and so was my initial proposal.
What causes this tick? I was under the impression that once there's a single task (not doing any syscalls) and the above issues are sorted, no more tick would happen.
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