Re: [PATCH [RT] 08/14] add a loop counter based timeout mechanism

[Andi Kleen]

> *) compute the context-switch pair time average for the system.  This is 
> your time threshold (CSt).

This is not a uniform time. Consider the difference between
context switch on the same hyperthread, context switch between cores
on a die, context switch between sockets, context switch between
distant numa nodes. You could have several orders of magnitude
between all those.

>
> *) For each lock, maintain an average hold-time (AHt) statistic (I am 
> assuming this can be done cheaply...perhaps not).

That would assume that the hold times are very uniform. But what happens
when you e.g. have a workload where 50% of the lock aquisitions are short 
and 30% are long? 

I'm a little sceptical of such "too clever" algorithms.

-Andi
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