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SubjectRe: nohz and strange sleep latencies
Date
On Sunday, 25 of November 2007, Rafael J. Wysocki wrote:
> On Saturday, 24 of November 2007, Pavel Machek wrote:
> > Hi!
> >
> > > > > but perhaps somehow we miss this fact and fail to turn off the lapic
> > > > > clockevents drivers?
> > > >
> > > > Ok, I guess I'm lost. If I offline second CPU, I immediately get
> > > > 1000Hz timer tick... is that expected?
> > >
> > > Hmm. No. I have no idea why this is happening.
> > >
> > > 34196 total events, 55.083 events/sec
> > > echo 0 >/sys/devices/system/cpu/cpu1/online
> > > 36073 total events, 54.679 events/sec
> >
> > Digging into process_32|64.c...
> >
> > 64:
> > while (1) {
> > while (!need_resched()) {
> > void (*idle)(void);
> >
> > if (__get_cpu_var(cpu_idle_state))
> > __get_cpu_var(cpu_idle_state) = 0;
> >
> > tick_nohz_stop_sched_tick();
> >
> > 32:
> > while (1) {
> > tick_nohz_stop_sched_tick();
> > while (!need_resched()) {
> > void (*idle)(void);
> >
> > if (__get_cpu_var(cpu_idle_state))
> > __get_cpu_var(cpu_idle_state) = 0;
> >
> > ...eek? Which one is wrong?
>
> Hm, it looks like you should have quoted more lines ...
>
> In the second case (32), the tick_nohz_stop_sched_tick() seems to be
> redundant, so I bet it's this one.

OTOH, the ARM's process.c is more similar to process_32.c ...
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