Re: [RFC PATCH 3/3] idle: store the idle state index in the struct rq

[Ingo Molnar]

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> [...]
>
> The reason Ingo took it out was that these measured numbers would 
> slightly vary from boot to boot making it hard to compare 
> performance numbers across boots.
> 
> There's something to be said for either case I suppose.

Yeah, so we could put the parameters back by measuring it in 
user-space via a nice utility in tools/, and by matching it to 
relevant hardware signatures (CPU type and cache sizes), plus doing 
some defaults for when we don't have any signature... possibly based 
on a fuzzy search to find the 'closest' system in the table of 
constants.

That would stabilize the boot-to-boot figures while still keeping most 
of the system specific-ness, in a maintainable fashion.

The downside is that we'd have to continuously maintain a table of all 
this info, with new entries added when new CPUs are introduced on the 
market. That's an upside too, btw.

Thanks,

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/