Re: [RFC] exponential update_wall_time

From: Roman Zippel
Date: Wed Sep 27 2006 - 19:05:05 EST


On Wed, 27 Sep 2006, john stultz wrote:

> Accumulate time in update_wall_time exponentially.
> This avoids long running loops seen with the dynticks patch
> as well as the problematic hang" seen on systems with broken
> clocksources.

This is the wrong approach, second_overflow() should be called every HZ
increment steps and your patch breaks this.
There are other approaches oo accommodate dyntick.
1. You could make HZ in ntp_update_frequency() dynamic and thus reduce the
frequency with which update_wall_time() needs to be called (Note that
other clock variables like cycle_interval have to be adjusted as well).
2. If dynticks stops the timer interrupt for a long time, it could
precalculate a few things, e.g. it could complete the second and then
advance the time in full seconds.

bye, Roman
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