rusage breakdown and cpu limits.

[Bruce Evans]

On Tue, 29 May 2007, Julian Elischer wrote:

> Jeff Roberson wrote:
>> I think I'm going to make the rusage struct per-thread and aggregate it on 
>> demand.  There will be a lot of code churn, but it will be simple. There 
>> are a few cases where which will be complicated, and cpulimit is one of 
>> them.
>
> So, there should be somewhere to store the aggregated stats from threads that 
> have already exited.

We already have that.  It is the per-process rusage.  There is already
delayed accumulation for tick counts (these are currently accumulated in
the rusage from the thread at context switch time).  There is also
delayed conversion of stats to the form needed by getrusage().  Stats
are kept in raw form as long as possible (forever if nothing calls
getrusage() or wait[34]() to look at them) to avoid conversion overhead
for them on every exit().  So there are many precedents for delayed
stats handling.

Bruce