On Tue, May 24, 2022 at 6:26 AM Peter Xu <peterx@xxxxxxxxxx> wrote: > > On Mon, May 23, 2022 at 05:18:32PM -0700, Zach O'Keefe wrote: > > (*) If we could verify that "never" THP mode was used _only_ for > > debugging, then I'd actually opt to ignore "never" in MADV_COLLAPSE. > > Some real time users may have used thp=never to make sure there's no > pgtable uncertainty in all cases (and pages will always be mlocked for the > RT apps, so pre-faulted). > Thanks for the great example here! > Debattably it's the same as TRANSPARENT_HUGEPAGE=n but the user might want > to use the same kernel with other purpose where thp could still be wanted? > I've no solid clue. It's just that as long as we have the knob taking > "never" as an option then people may be using it, I'm afraid. > > "no" is indeed stronger than "yes" in many cases, at least for thp it's > always like that: thp=never will guarantee no thp globally, while > thp=always will only provide thp when it's still possible. The same to > MADV_[NO]HUGEPAGE but just for vmas. From that POV I think your current > plan looks reasonable on respecting "no"s more than "yes"s for both layers. > This makes sense to me. Best to be safe / follow existing "strong no" convention. Again, thanks for taking the time to read and provide feedback - very much appreciated. Best, Zach > Thanks, > > -- > Peter Xu >
