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| author | Mike Rapoport <rppt@linux.vnet.ibm.com> | 2018-04-24 09:40:27 +0300 |
|---|---|---|
| committer | Jonathan Corbet <corbet@lwn.net> | 2018-04-27 17:19:44 -0600 |
| commit | 8b898fd11414a365b1e024d027a76f6bb0b12b6e (patch) | |
| tree | e9f391b4549c0e4d76b67d5553a8b422515f781b /Documentation/vm/ksm.rst | |
| parent | 2a695ca412943b88abde5dda0d5b6876fd154ac8 (diff) | |
| download | linux-8b898fd11414a365b1e024d027a76f6bb0b12b6e.tar.bz2 | |
docs/vm: ksm: udpate description of stable_node_{dups,chains}
Remove implementation details from sysfs parameter descriptions.
Also move the paragraph discussing fragmentation issues and their possible
solution to the "Design" section.
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/vm/ksm.rst')
| -rw-r--r-- | Documentation/vm/ksm.rst | 21 |
1 files changed, 10 insertions, 11 deletions
diff --git a/Documentation/vm/ksm.rst b/Documentation/vm/ksm.rst index 18d7c710a5f3..afcf5a8fc4a5 100644 --- a/Documentation/vm/ksm.rst +++ b/Documentation/vm/ksm.rst @@ -170,10 +170,9 @@ pages_volatile full_scans how many times all mergeable areas have been scanned stable_node_chains - number of stable node chains allocated, this is effectively the number of KSM pages that hit the ``max_page_sharing`` limit stable_node_dups - number of stable node dups queued into the stable_node chains + number of duplicated KSM pages A high ratio of ``pages_sharing`` to ``pages_shared`` indicates good sharing, but a high ratio of ``pages_unshared`` to ``pages_sharing`` @@ -185,15 +184,6 @@ The maximum possible ``pages_sharing/pages_shared`` ratio is limited by the ``max_page_sharing`` tunable. To increase the ratio ``max_page_sharing`` must be increased accordingly. -The ``stable_node_dups/stable_node_chains`` ratio is also affected by the -``max_page_sharing`` tunable, and an high ratio may indicate fragmentation -in the stable_node dups, which could be solved by introducing -fragmentation algorithms in ksmd which would refile rmap_items from -one stable_node dup to another stable_node dup, in order to free up -stable_node "dups" with few rmap_items in them, but that may increase -the ksmd CPU usage and possibly slowdown the readonly computations on -the KSM pages of the applications. - Design ====== @@ -247,6 +237,15 @@ deduplication factor at the expense of slower worst case for rmap walks for any KSM page which can happen during swapping, compaction, NUMA balancing and page migration. +The ``stable_node_dups/stable_node_chains`` ratio is also affected by the +``max_page_sharing`` tunable, and an high ratio may indicate fragmentation +in the stable_node dups, which could be solved by introducing +fragmentation algorithms in ksmd which would refile rmap_items from +one stable_node dup to another stable_node dup, in order to free up +stable_node "dups" with few rmap_items in them, but that may increase +the ksmd CPU usage and possibly slowdown the readonly computations on +the KSM pages of the applications. + The whole list of stable_node "dups" linked in the stable_node "chains" is scanned periodically in order to prune stale stable_nodes. The frequency of such scans is defined by |