Messages in this thread | | | From | "Nikita V. Youshchenko" <> | Subject | Re: [rt-preempt / powerpc] Looks like tick_sched_timer() is a major latency source | Date | Wed, 24 Jun 2009 00:01:47 +0400 |
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> > I tried hard to identify the latency source, and at some moment > > discovered tick_sched_timer() from kernel/time/tick-sched.c. This > > routine is called from timer interrupt with hardware interrupts > > disabled, and may execute for 50 us and more. > > > > Could someone please comment on this? > > Did you have CONFIG_NOHZ enabled ? If yes, please disable.
I have disabled CONFIG_NOHZ long ago, since it really influences latency.
> > Is it possible to move (part of) tick_sched_timer() call tree out of > > hardware-interrupts-disabled context without breaking things? > > Yes, we can move things out and split the irq disabled regions. One > particular thing which can be split out is the time update, which we > already had in the timer softirq at some point, but we moved it back > as it showed problems with NTP stability. It's one of the things which > can be revisited. The whole call chain needs some investigation, but > that's not in my main focus now.
Is that code with time update split out available anywhere?
Nikita
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