Martin J. Bligh wrote:
>>Because of the recent discussion about latency in the kernel I asked 
>>William Lee Irwin III to help create some instrumentation to determine 
>>where in the kernel there were still sustained periods of non-preemptible 
>>code. He hacked together this simple patch which times periods according 
>>to the preempt count. Hopefully we can use this patch in the advice of 
>>Linus to avoid the "mental masturbation" at guessing where latency is 
>>and track down real problem areas.
> 
> 
> Is this much different from Rick's schedstat's work, which was itself based
> on some earlier patches by Bill? I'd hate to end up with two sets of patches,
> and schedstats seemed pretty comprehensive to me. He's on vacation, but his
> stuff is here, if you want to take a look:
> 
> http://eaglet.rain.com/rick/linux/schedstats/

No I remember his work and this is tackling it via a different area if I 
recall correctly. He was looking at scheduler latencies as opposed to 
non-preemptible kernel code.

Con