On Tue 15-10-24 08:58:59, Suren Baghdasaryan wrote: > On Tue, Oct 15, 2024 at 8:42 AM David Hildenbrand <david@xxxxxxxxxx> wrote: [...] > > Right, I think what John is concerned about (and me as well) is that > > once a new feature really needs a page flag, there will be objection > > like "no you can't, we need them for allocation tags otherwise that > > feature will be degraded". > > I do understand your concern but IMHO the possibility of degrading a > feature should not be a reason to always operate at degraded capacity > (which is what we have today). If one is really concerned about > possible future regression they can set > CONFIG_PGALLOC_TAG_USE_PAGEFLAGS=n and keep what we have today. That's > why I'm strongly advocating that we do need > CONFIG_PGALLOC_TAG_USE_PAGEFLAGS so that the user has control over how > this scarce resource is used. I really do not think users will know how/why to setup this and I wouldn't even bother them thinking about that at all TBH. This is an implementation detail. It is fine to reuse unused flags space as a storage as a performance optimization but why do you want users to bother with that? Why would they ever want to say N here? -- Michal Hocko SUSE Labs
