On Mon, Sep 15, 2025 at 01:10:22PM +0200, David Hildenbrand wrote: > On 15.09.25 12:59, Lorenzo Stoakes wrote: > > On Mon, Sep 15, 2025 at 12:52:53PM +0200, David Hildenbrand wrote: > > > On 15.09.25 12:48, Lorenzo Stoakes wrote: > > > > On Mon, Sep 15, 2025 at 12:44:34PM +0200, David Hildenbrand wrote: > > > > > > > > Mapping that to actual THP sizes (#pages in a thp) on an arch > > > > > > > > will be easy. > > > > > > > > > > > > > > And at different mTHP levels too right? > > > > > > > > > > > > > > > > > > > Another point here, since we have to keep: > > > > > > > > > > > > /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none > > > > > > > > > > > > Around, and users will try to set values there, presumably we will > > > > > > now add: > > > > > > > > > > > > /sys/kernel/mm/transparent_hugepage/khugepaged/eagerness > > > > > > > > > > > > How will we map <-> the two tunables? > > > > > > > > > > Well, the easy case if someone updates eagerness, then we simply et > > > > > it to > > > > > whatever magic value we compute and document. > > > > > > > > > > The other direction is more problematic, likely we'll simply warn and > > > > > do > > > > > something reasonable (map it to whatever eagerness scale is closest or > > > > > simply indicate it as "-1" -- user intervened or sth like that) > > > > > > > > I don't love the idea of a -1 situation, as that's going to create some > > > > confusion. > > > > > > swapiness also has a "max" parameter, so we could just say "override" /" > > > disabled" / whatever? > > > > I don't love the user being able to override this though, let's just nuke > > their > > ability to set this pleeeease. > > > > Because if they can override it, then we have to do some deeply nasty > > scaling > > for mTHP again. > > There are ways to have it working internally, just using a different "scale" > instead of the 100 -> 50 -> 25 etc.
Right. I mean with the exponential scale we could just algorithimically figure out what the eagerness should be. > > I am afraid we cannot change the parameter to ignore other values because of > the interaction with the shrinker that easily .... we might be able to > detracted at wait a bunch of kernel releases probably. :( BTW 'Detracted at wait'? :P You mean we might be able to remove after a few releases? > > -- > Cheers > > David / dhildenb > Cheers, Lorenzo
