Messages in this thread | | | Date | Thu, 18 Dec 2014 15:43:06 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: [PATCH] tick/powerclamp: Remove tick_nohz_idle abuse |
| |
On Thu, 18 Dec 2014, Eduardo Valentin wrote: > > The real solution is to fix the powerclamp driver by rewriting it with > > a sane concept, but that's beyond the scope of this. > > > > Do you have suggestions on what exactly is the expected rewriting or the > correct sane concepts?
There was quite some discussion about this in this very thread.
> > So the only solution for now is to remove the calls into the core NOHZ > > code from the powerclamp trainwreck along with the exports. > > > > Fixes: d6d71ee4a14a "PM: Introduce Intel PowerClamp Driver" > > If I got it right, the driver is currently broken due to changes in NOHZ > core. So, does this patch fix power clamp behavior ?
The driver has been broken forever. It just worked by chance.
Now a very well justified and correct change in the core code exposed that wreckage. So we have 2 choices:
1) Get rid of the abuse and let powerclamp deal with the problem.
2) Revert a correct patch for the sake of a 'works by chance' driver or put hacky workarounds in the core. Either of that will just paper over the real root cause until the next thing breaks in subtle ways.
#1 is the only sane decision. We cannot deal with misdesigned driver code in the NOHZ core.
> If I got your proposal right, in the end power clamp will be still > broken, but at least won't be abusing NOHZ. Is that what you are > proposing?
Yes, the design of powerclamp stays broken, but the NOHZ abuse is gone. powerclamp will work, but it can't benefit from the possible longer idle times anymore.
Thanks,
tglx
| |