diff options
Diffstat (limited to 'Documentation/mm/split_page_table_lock.rst')
| -rw-r--r-- | Documentation/mm/split_page_table_lock.rst | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/Documentation/mm/split_page_table_lock.rst b/Documentation/mm/split_page_table_lock.rst index e4f6972eb6c0..cc3cd46abd1b 100644 --- a/Documentation/mm/split_page_table_lock.rst +++ b/Documentation/mm/split_page_table_lock.rst @@ -4,7 +4,7 @@ Split page table lock Originally, mm->page_table_lock spinlock protected all page tables of the mm_struct. But this approach leads to poor page fault scalability of -multi-threaded applications due high contention on the lock. To improve +multi-threaded applications due to high contention on the lock. To improve scalability, split page table lock was introduced. With split page table lock we have separate per-table lock to serialize @@ -16,9 +16,13 @@ There are helpers to lock/unlock a table and other accessor functions: - pte_offset_map_lock() maps PTE and takes PTE table lock, returns pointer to PTE with pointer to its PTE table lock, or returns NULL if no PTE table; - - pte_offset_map_nolock() + - pte_offset_map_ro_nolock() maps PTE, returns pointer to PTE with pointer to its PTE table lock (not taken), or returns NULL if no PTE table; + - pte_offset_map_rw_nolock() + maps PTE, returns pointer to PTE with pointer to its PTE table + lock (not taken) and the value of its pmd entry, or returns NULL + if no PTE table; - pte_offset_map() maps PTE, returns pointer to PTE, or returns NULL if no PTE table; - pte_unmap() @@ -58,7 +62,7 @@ Support of split page table lock by an architecture =================================================== There's no need in special enabling of PTE split page table lock: everything -required is done by pagetable_pte_ctor() and pagetable_pte_dtor(), which +required is done by pagetable_pte_ctor() and pagetable_dtor(), which must be called on PTE table allocation / freeing. Make sure the architecture doesn't use slab allocator for page table @@ -69,7 +73,7 @@ PMD split lock only makes sense if you have more than two page table levels. PMD split lock enabling requires pagetable_pmd_ctor() call on PMD table -allocation and pagetable_pmd_dtor() on freeing. +allocation and pagetable_dtor() on freeing. Allocation usually happens in pmd_alloc_one(), freeing in pmd_free() and pmd_free_tlb(), but make sure you cover all PMD table allocation / freeing |