clocksource: Limit number of CPUs checked for clock synchronization
Currently, if skew is detected on a clock marked CLOCK_SOURCE_VERIFY_PERCPU, that clock is checked on all CPUs. This is thorough, but might not be what you want on a system with a few tens of CPUs, let alone a few hundred of them. Therefore, by default check only up to eight randomly chosen CPUs. Also provide a new clocksource.verify_n_cpus kernel boot parameter. A value of -1 says to check all of the CPUs, and a non-negative value says to randomly select that number of CPUs, without concern about selecting the same CPU multiple times. However, make use of a cpumask so that a given CPU will be checked at most once. Suggested-by: Thomas Gleixner <tglx@linutronix.de> # For verify_n_cpus=1. Signed-off-by:Paul E. McKenney <paulmck@kernel.org> Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> Acked-by:
Feng Tang <feng.tang@intel.com> Link: https://lore.kernel.org/r/20210527190124.440372-3-paulmck@kernel.org
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