On Thu, Jan 04, 2001 at 01:39:57PM -0800, Nigel Gamble wrote:
> Experience has shown that adaptive spinlocks are not worth the extra
> overhead (if you mean the type that spin for a short time
> and then decide to sleep). It is better to use spin_lock_irqsave()
> (which, by definition, disables kernel preemption without the need
> to set a no-preempt flag) to protect regions where the lock is held
> for a maximum of around 100us, and to use a sleeping mutex lock for
> longer regions. This is what I'm working towards.
What experience ? Only real-time latency testing or SMP scalability
testing?
The case I was thinking about is a heavily contended lock like the
inode semaphore of a file that is used by several threads on several
CPUs in parallel or the mm semaphore of a often faulted shared mm.
It's not an option to convert them to a spinlock, but often the delays
are short enough that a short spin could make sense.
-Andi
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This archive was generated by hypermail 2b29 : Sun Jan 07 2001 - 21:00:19 EST