On Wed, Apr 17, 2024 at 10:11:11PM +0800, Lance Yang wrote: > When the user no longer requires the pages, they would use madvise(madv_free) > to mark the pages as lazy free. IMO, they would not typically rewrite to the > given range. > > At present, a PMD-mapped THP marked as lazyfree during shrink_folio_list() > is unconditionally split, which may be unnecessary. If the THP is exclusively > mapped and clean, and the PMD associated with it is also clean, then we can > attempt to remove the PMD mapping from it. This change will improve the > efficiency of memory reclamation in this case. > > On an Intel i5 CPU, reclaiming 1GiB of PMD-mapped THPs using > mem_cgroup_force_empty() results in the following runtimes in seconds > (shorter is better): > > -------------------------------------------- > | Old | New | Change | > -------------------------------------------- > | 0.683426 | 0.049197 | -92.80% | > -------------------------------------------- > > Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx> > --- > include/linux/huge_mm.h | 1 + > include/linux/rmap.h | 1 + > mm/huge_memory.c | 2 +- > mm/rmap.c | 81 +++++++++++++++++++++++++++++++++++++++++ > mm/vmscan.c | 7 ++++ > 5 files changed, 91 insertions(+), 1 deletion(-) I'm confused why we need all this extra code. If we remove a folio from the pagecache, we can just call truncate_inode_folio() and unmap_mapping_folio() takes care of all the necessary unmappings. Why can't you call unmap_mapping_folio() here?
