[prev in list] [next in list] [prev in thread] [next in thread] 

List:       linux-kernel
Subject:    Re: [PATCH [RT] 08/14] add a loop counter based timeout mechanism
From:       Andi Kleen <ak () suse ! de>
Date:       2008-02-23 12:31:00
Message-ID: 20080223123100.GB9021 () bingen ! suse ! de
[Download RAW message or body]

> *) 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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
[prev in list] [next in list] [prev in thread] [next in thread]