On Wed, 12 Dec 2018 at 10:46, Peter Zijlstra [off-list ref] wrote:

On Tue, Dec 11, 2018 at 10:51:48AM +0100, Rafael J. Wysocki wrote:

quoted

On Mon, Dec 10, 2018 at 11:51 PM Peter Zijlstra [off-list ref] wrote:

quoted

quoted

Dunno; it could be cold cachelines, at which point it can be fairly
expensive. Also, being stuck with API is fairly horrible if you want to
'fix' it.

All of the cache lines involved should've been touched earlier in this
code path by the governor.  At least menu and the new one both touch
them.

The API part I'm not too worried about.  I know it is useful and two
other people have told that to me already. :-)

Like said on IRC; I mostly wanted to raise the issue of overhead due to
stats and ABI -- it's something I've been bitten by too many times :/

If you're confident you're hitting the same lines with the already
extant accouning (time and usage) and you cannot make the whole lot
conditional because of ABI (bah) then I'll not stand in the way here.

I agree the numbers are useful, I'm just weary of overhead.

I tend to agree. So then why not move this to debugfs, it seems like
it's really there it belongs. No?

Kind regards
Uffe