[mmmooo]

well redhat back ported it to their 2.6.x kernels, which, one could consider, can cause a giant regression due to a minor kernel patch (assuming you are using swappiness=0). As said by others, swappiness=0 isn't as great an idea as some people claim in the first place.

[josho]

I don't follow Red Hat all that closely anymore, but they have had a long standing policy of back porting changes to kernels. In fact, this is part of why they've been successful in enterprise: RH provides long term support on a stable kernel that receives key fixes from upstream kernel versions.

[Sanddancer]

The problem is that this wasn't a bug fix, but a behavior change. Worse, it's an undocumented behavior change. This is the sort of thing that can and should be documented.

[mmmooo]

Yep, and/or not back-ported.