On Thu, Sep 10, 2026 at 02:27:28PM +0800, Baolin Wang wrote: > > > On 9/9/26 6:41 PM, Kiryl Shutsemau wrote: > > On Wed, Sep 09, 2026 at 05:55:01PM +0800, Baolin Wang wrote: > > > > > > > > > On 9/8/26 8:50 PM, Kiryl Shutsemau wrote: > > > > From: "Kiryl Shutsemau (Meta)" <[email protected]> > > > > > > > > __madvise_collapse() turns THP off before each MADV_COLLAPSE, both to > > > > keep > > > > khugepaged out of the range and to prove MADV_COLLAPSE ignores the > > > > setting. > > > > It clears the global controls only, which is no longer enough. A > > > > per-order > > > > control overrides them, and -s, which makes the cases fault in folios of > > > > one order, leaves that order's control at "always". khugepaged then > > > > collapses the very range the case is working on, and the case fails on a > > > > collapse that was interfered with rather than refused. > > > > > > Right. So I think the correct fix tag is b7f16963efe7 ("mm/khugepaged: run > > > khugepaged for all orders"), because before this commit, khugepaged would > > > not try to collapse this range since it only checked whether the PMD order > > > was suitable for collapse. > > > > Agreed. The series is in mm-new already; if a respin is needed I will use > > that tag. > > > > > > @@ -547,9 +547,16 @@ static void __madvise_collapse(const char *msg, > > > > char *p, int nr_hpages, > > > > /* > > > > * Prevent khugepaged interference and tests that MADV_COLLAPSE > > > > * ignores /sys/kernel/mm/transparent_hugepage/enabled > > > > + * > > > > + * "inherit" rather than "never" so that MADV_COLLAPSE on shmem > > > > still > > > > + * finds an order to build. > > > > */ > > > > settings.thp_enabled = THP_NEVER; > > > > settings.shmem_enabled = SHMEM_NEVER; > > > > + for (i = 0; i < NR_ORDERS; i++) { > > > > + settings.hugepages[i].enabled = THP_INHERIT; > > > > + settings.shmem_hugepages[i].enabled = SHMEM_INHERIT; > > > > + } > > > > > > This looks like a workaround to me. Shouldn't we fix this in shmem > > > instead? > > > > Good point. > > > > It can be a follow-up patch. Do you want to make a proper shmem.c fix > > and update the selftest along with it? > > Either way works for me.
Please, do it as a standlone shmem fix, plus selftest update to reflect the change. -- Kiryl Shutsemau / Kirill A. Shutemov
