On 3/23/26 22:02, Matthew Wilcox wrote: > On Mon, Mar 23, 2026 at 04:24:26PM -0400, Zi Yan wrote: >> On 23 Mar 2026, at 16:13, David Hildenbrand (Arm) wrote: >>> I assume so, because for executables you would have to be lucky to get a >>> PMD THP? So I don't see the non-khugepaged large folio support on par >>> with khugepaged support. > > Not necessarily that lucky; if you set VM_HUGEPAGE, > do_sync_mmap_readahead() will allocate PMD-sized folios automatically. > On busy database servers (and is there any other kind?), khugepaged > takes too long to run and find opportunities to collapse text pages. > Like, days.
Yes, in particular given that the default khugepaged settings are awful. > >> It is more like turning on READ_ONLY_THP_FOR_FS by default for >> FS with large folio support instead of removing it. >> >> OK, I will give it another try. > > I think the test needs to be: > > if (mapping_max_folio_order(mapping) >= PMD_ORDER) > > as there can be cases of filesystems which support up to, say, 64KiB, > but not all the way up to 2MiB. I disapprove of this situation, but > this is where we are right now. Right, that's what I had in mind. -- Cheers, David
