On Wed, 2 Feb 2022 at 02:42, Liam Howlett <liam.howlett@xxxxxxxxxx> wrote: > > From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx> > > The maple tree is an RCU-safe range based B-tree designed to use modern > processor cache efficiently. There are a number of places in the kernel > that a non-overlapping range-based tree would be beneficial, especially > one with a simple interface. The first user that is covered in this > patch set is the vm_area_struct, where three data structures are > replaced by the maple tree: the augmented rbtree, the vma cache, and the > linked list of VMAs in the mm_struct. The long term goal is to reduce > or remove the mmap_sem contention. > > The tree has a branching factor of 10 for non-leaf nodes and 16 for leaf > nodes. With the increased branching factor, it is significantly shorter than > the rbtree so it has fewer cache misses. The removal of the linked list > between subsequent entries also reduces the cache misses and the need to pull > in the previous and next VMA during many tree alterations. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> > Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> > --- > Documentation/core-api/index.rst | 1 + > Documentation/core-api/maple_tree.rst | 196 + > MAINTAINERS | 12 + > include/linux/maple_tree.h | 673 ++ > include/trace/events/maple_tree.h | 123 + > lib/Kconfig.debug | 9 + > lib/Makefile | 3 +- > lib/maple_tree.c | 6943 +++++++++++++++++ > tools/testing/radix-tree/.gitignore | 2 + > tools/testing/radix-tree/Makefile | 13 +- > tools/testing/radix-tree/generated/autoconf.h | 1 + > tools/testing/radix-tree/linux/maple_tree.h | 7 + > tools/testing/radix-tree/maple.c | 59 + > .../radix-tree/trace/events/maple_tree.h | 3 + > 14 files changed, 8042 insertions(+), 3 deletions(-) > create mode 100644 Documentation/core-api/maple_tree.rst > create mode 100644 include/linux/maple_tree.h > create mode 100644 include/trace/events/maple_tree.h > create mode 100644 lib/maple_tree.c > create mode 100644 tools/testing/radix-tree/linux/maple_tree.h > create mode 100644 tools/testing/radix-tree/maple.c > create mode 100644 tools/testing/radix-tree/trace/events/maple_tree.h ... > +Allocating Nodes > +---------------- > + > +Allocations are usually handled internally to the tree, however if allocations > +need to occur before a write occurs then calling mas_entry_count() will > +allocate the worst-case number of needed nodes to insert the provided number of > +ranges. This also causes the tree to enter mass insertion mode. Once > +insertions are complete calling mas_destroy() on the maple state will free the > +unused allocations. mas_entry_count() has been renamed to mas_expected_entries(). (Note: test code is still using mas_entry_count()). Cheers, Mark
