On Mon, Dec 16, 2024 at 10:31 AM Dev Jain <dev.jain@xxxxxxx> wrote: > > +Nico, apologies, forgot to CC you. Hey Dev, Happy New Year! Thanks! I'm trying to apply/test your patches, but am failing to apply them due to mm-unstable which has "unstable" sha values, making applying them difficult. Could you share a public git repo to your patches? Also, have you seen any issues with your patches? My version of khugepaged mTHP support was mostly done before the holidays but I haven't posted due to some issues with (BAD PAGE) refcount issues when trying to reclaim pages that I haven't found the cause of yet. -- Nico > > On 16/12/24 10:20 pm, Dev Jain wrote: > > This patchset extends khugepaged from collapsing only PMD-sized THPs to > > collapsing anonymous mTHPs. > > > > mTHPs were introduced in the kernel to improve memory management by allocating > > chunks of larger memory, so as to reduce number of page faults, TLB misses (due > > to TLB coalescing), reduce length of LRU lists, etc. However, the mTHP property > > is often lost due to CoW, swap-in/out, and when the kernel just cannot find > > enough physically contiguous memory to allocate on fault. Henceforth, there is a > > need to regain mTHPs in the system asynchronously. This work is an attempt in > > this direction, starting with anonymous folios. > > > > In the fault handler, we select the THP order in a greedy manner; the same has > > been used here, along with the same sysfs interface to control the order of > > collapse. In contrast to PMD-collapse, we (hopefully) get rid of the mmap_write_lock(). > > > > --------------------------------------------------------- > > Testing > > --------------------------------------------------------- > > > > The set has been build tested on x86_64. > > For Aarch64, > > 1. mm-selftests: No regressions. > > 2. Analyzing with tools/mm/thpmaps on different userspace programs mapping > > aligned VMAs of a large size, faulting in basepages/mTHPs (according to sysfs), > > and then madvise()'ing the VMA, khugepaged is able to 100% collapse the VMAs. > > > > This patchset is rebased on mm-unstable (e7e89af21ffcfd1077ca6d2188de6497db1ad84c). > > > > Some points to be noted: > > 1. Some stats like pages_collapsed for khugepaged have not been extended for mTHP. > > I'd welcome suggestions on any updation, or addition to the sysfs interface. > > 2. Please see patch 9 for lock handling. > > > > Dev Jain (12): > > khugepaged: Rename hpage_collapse_scan_pmd() -> ptes() > > khugepaged: Generalize alloc_charge_folio() > > khugepaged: Generalize hugepage_vma_revalidate() > > khugepaged: Generalize __collapse_huge_page_swapin() > > khugepaged: Generalize __collapse_huge_page_isolate() > > khugepaged: Generalize __collapse_huge_page_copy_failed() > > khugepaged: Scan PTEs order-wise > > khugepaged: Abstract PMD-THP collapse > > khugepaged: Introduce vma_collapse_anon_folio() > > khugepaged: Skip PTE range if a larger mTHP is already mapped > > khugepaged: Enable sysfs to control order of collapse > > selftests/mm: khugepaged: Enlighten for mTHP collapse > > > > include/linux/huge_mm.h | 2 + > > mm/huge_memory.c | 4 + > > mm/khugepaged.c | 445 +++++++++++++++++------- > > tools/testing/selftests/mm/khugepaged.c | 5 +- > > 4 files changed, 319 insertions(+), 137 deletions(-) > > >
