# Re: \[PATCH\] mm: introduce MADV\_CLR\_HUGEPAGE - From: Vlastimil Babka \ - Date: 2017-05-24 11:32:52 - List: linux-api - Page: https://ratatoskr.run/linux-api/2017/05/5004130 - Thread: https://ratatoskr.run/linux-mm/2017/05/5001191/t.md ```text On 05/24/2017 12:39 PM, Mike Rapoport wrote: >> Hm so the prctl does: >> >> if (arg2) >> me->mm->def_flags |= VM_NOHUGEPAGE; >> else >> me->mm->def_flags &= ~VM_NOHUGEPAGE; >> >> That's rather lazy implementation IMHO. Could we change it so the flag >> is stored elsewhere in the mm, and the code that decides to (not) use >> THP will check both the per-vma flag and the per-mm flag? > > I afraid I don't understand how that can help. > What we need is an ability to temporarily disable collapse of the pages in > VMAs that do not have VM_*HUGEPAGE flags set and that after we re-enable > THP, the vma->vm_flags for those VMAs will remain intact. That's what I'm saying - instead of implementing the prctl flag via mm->def_flags (which gets permanently propagated to newly created vma's but e.g. doesn't affect already existing ones), it would be setting a flag somewhere in mm, which khugepaged (and page faults) would check in addition to the per-vma flags. > -- > Sincerely yours, > Mike. > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org ```