* Vasily Gorbik <gor@xxxxxxxxxxxxx> [220226 21:23]: > On Tue, Feb 15, 2022 at 02:37:44PM +0000, Liam Howlett wrote: > > 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. > > > > This patch is based on v5.17-rc4 > > > > git: https://github.com/oracle/linux-uek/tree/howlett/maple/20220214 > > Hi Liam, > > this patch series completely breaks s390. Besides endianess issue > in maple trees reported here: > > https://lore.kernel.org/all/your-ad-here.call-01645924312-ext-0398@work.hours/ > > and with this endianess issue fixed (fixup from here ^^^) we still get numerous > KASAN reports starting with > > [PATCH v6 10/71] mm: Start tracking VMAs with maple tree Thanks for looking at this. That commit had two issues which I was debugging on parisc for most of last week. The first is that I was not actually writing the stack expansion to the maple tree in that commit - it was added in a later commit. The second issue which was most likely causing your crashes was the calculation for the gap in unmapped_area_topdown(). With the maple tree (3dea5db7fbb5), I am able to boot parisc and s390 virtual machines. Although, the issue which Hugh discusses in detail still exists [1]. The latest maple tree can be found on github [2]. I am still investigating why the heap changed locations on parisc to ensure it's not of issue. 1: https://lore.kernel.org/all/5f8f4f-ad63-eb-fd73-d48748af8a76@xxxxxxxxxx/ 2: https://github.com/oracle/linux-uek/tree/maple/mainline Regards, Liam
