diff options
Diffstat (limited to 'mm/ksm.c')
| -rw-r--r-- | mm/ksm.c | 34 |
1 files changed, 31 insertions, 3 deletions
@@ -51,7 +51,9 @@ #define DO_NUMA(x) do { } while (0) #endif -/* +/** + * DOC: Overview + * * A few notes about the KSM scanning process, * to make it easier to understand the data structures below: * @@ -67,6 +69,21 @@ * this tree is fully assured to be working (except when pages are unmapped), * and therefore this tree is called the stable tree. * + * The stable tree node includes information required for reverse + * mapping from a KSM page to virtual addresses that map this page. + * + * In order to avoid large latencies of the rmap walks on KSM pages, + * KSM maintains two types of nodes in the stable tree: + * + * * the regular nodes that keep the reverse mapping structures in a + * linked list + * * the "chains" that link nodes ("dups") that represent the same + * write protected memory content, but each "dup" corresponds to a + * different KSM page copy of that content + * + * Internally, the regular nodes, "dups" and "chains" are represented + * using the same :c:type:`struct stable_node` structure. + * * In addition to the stable tree, KSM uses a second data structure called the * unstable tree: this tree holds pointers to pages which have been found to * be "unchanged for a period of time". The unstable tree sorts these pages @@ -823,6 +840,17 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma, return err; } +static inline struct stable_node *page_stable_node(struct page *page) +{ + return PageKsm(page) ? page_rmapping(page) : NULL; +} + +static inline void set_page_stable_node(struct page *page, + struct stable_node *stable_node) +{ + page->mapping = (void *)((unsigned long)stable_node | PAGE_MAPPING_KSM); +} + #ifdef CONFIG_SYSFS /* * Only called through the sysfs control interface: @@ -1049,7 +1077,7 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page, * No need to notify as we are downgrading page table to read * only not changing it to point to a new page. * - * See Documentation/vm/mmu_notifier.txt + * See Documentation/vm/mmu_notifier.rst */ entry = ptep_clear_flush(vma, pvmw.address, pvmw.pte); /* @@ -1145,7 +1173,7 @@ static int replace_page(struct vm_area_struct *vma, struct page *page, * No need to notify as we are replacing a read only page with another * read only page with the same content. * - * See Documentation/vm/mmu_notifier.txt + * See Documentation/vm/mmu_notifier.rst */ ptep_clear_flush(vma, addr, ptep); set_pte_at_notify(mm, addr, ptep, newpte); |
