This option wasn't for speed. It was because there were specific
intervals that he wanted to record stats.
No, I don't believe that anyone has studied stat overhead, but in
general, it's just incrementing a number, and it's only stats that get
touched a lot that matter. So, stuff that gets executed every cycle
in the cpu might matter, but little else. It's not worth the effort
to turn some on and off.
Nate
On Thu, Feb 14, 2008 at 6:17 PM, Korey Sewell <[EMAIL PROTECTED]> wrote:
> > As for selectively dumping some stats and not dumping others we don't
> > support anything like that currently.
> Have we ever studied the Statistics overhead in M5?
>
> I may be wrong on this, but it seems to me that if every SimObject has
> some stats, if all stats in SimObjects are kept without option, and if
> M5 is heavily modular than that means that being able to toggle
> exactly which stats are kept and not kept during any simulation could
> be pretty important for simulation performance.
>
> Additionally, the performance degradation of not including this
> capability would continue to increase as people try to simulate
> 10s/100s of cores and each core/cache has it's own particular set of
> stats it's constantly trying to keep updated.
>
> If this is indeed a problem worth looking at,
> then any solution would probably be complicated (Python/SWIG magic?)
> or it would be messy in the code (compiler directives everywhere?).
>
> The compiler directives method probably wouldnt be very effective
> because then if you have two objects of the same type and want to
> collects stats from one and not the other you really aren't able to do
> that. Also, you wouldn't be able to toggle different stats for
> different objects at run-time.
>
> Nate's example of enabling/disabling could be a way to make it work
> asyou could set that in the regStats() function based on some
> "stats_on" parameter defined in the SimObject class.
>
> However, if you have code like:
>
> void operator++() { if (enabled) data()->inc(1, params); }
> is that really significantly faster then figuring out a way to compile it
> out?
>
> I dont know, but this may be something to look into after the tutorial...
>
> --
> ----------
> Korey L Sewell
> Graduate Student - PhD Candidate
> Computer Science & Engineering
> University of Michigan
>
>
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>
>
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