Re: Potential scheduler regression

From: Ingo Molnar
Date: Tue Jul 11 2017 - 04:30:26 EST

* Ben Guthro <ben@xxxxxxxxxx> wrote:

> > If people have experience with these in the "enterprise" distros, or any other
> > tree, and want to provide me with backported, and tested, patches, I'll be
> > glad to consider them for stable kernels.
> >
> > thanks,
> >
> > greg k-h
> I tried to do a simple cherry-pick of the suggested patches - but they
> apply against files that don't exist in the 4.9 series.

I think there are only two strategies to maintain a backport which work in the
long run:

- insist on the simplest fixes and pure cherry-picks

- or pick up _everything_ to sync up the two versions.

The latter would mean a lot of commits - and I'm afraid it would also involve the
scheduler header split-up, which literally involves hundreds of files plus
perpetual build-breakage risk, so it's a no-no.

> In my release of 4.9 - I'm planning on doing the simpler revert of 1b568f0aab
> that introduced the performance degradation, rather than pulling in lots of code
> from newer kernels.

That sounds much saner - I'd even Ack that approach for -stable as a special
exception, than to complicate things with excessive backports.