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author | Mike Rapoport <rppt@linux.vnet.ibm.com> | 2018-04-24 08:40:22 +0200 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2018-04-28 01:19:24 +0200 |
commit | 5a2ca3efe6a07a155674ccbe36ad66d0840ce2c1 (patch) | |
tree | c59d453ae58f0614e6c92b4b737ca1a9703605de /mm/ksm.c | |
parent | Documentation: driver-api: fix device_connection.rst kernel-doc error (diff) | |
download | linux-5a2ca3efe6a07a155674ccbe36ad66d0840ce2c1.tar.xz linux-5a2ca3efe6a07a155674ccbe36ad66d0840ce2c1.zip |
mm/ksm: docs: extend overview comment and make it "DOC:"
The existing comment provides a good overview of KSM implementation. Let's
update it to reflect recent additions of "chain" and "dup" variants of the
stable tree nodes and mark it as "DOC:" for inclusion into the KSM
documentation.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'mm/ksm.c')
-rw-r--r-- | mm/ksm.c | 19 |
1 files changed, 18 insertions, 1 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 |