On Tue, Aug 22, 2023 at 11:34:19AM -0700, Hugh Dickins wrote: > (Yes, the locking is a bit confusing: but mainly for the unrelated reason, > that with the split locking configs, we never quite know whether this lock > is the same as that lock or not, and so have to be rather careful.) Is it time to remove the PTE split locking config option? I believe all supported architectures have at least two levels of page tables, so if we have split ptlocks, ptl and pml are always different from each other (it's just that on two level machines, pmd == pud == p4d == pgd). With huge thread counts now being the norm, it's hard to see why anybody would want to support SMP and !SPLIT_PTE_PTLOCKS. To quote the documentation ... Split page table lock for PTE tables is enabled compile-time if CONFIG_SPLIT_PTLOCK_CPUS (usually 4) is less or equal to NR_CPUS. If split lock is disabled, all tables are guarded by mm->page_table_lock. You can barely buy a wrist-watch without eight CPUs these days.
