| From: Stefan Roesch <shr@devkernel.io> |
| Subject: mm/ksm: document smart scan mode |
| Date: Mon, 25 Sep 2023 21:09:38 -0700 |
| |
| This adds documentation for the smart scan mode of KSM. |
| |
| [akpm@linux-foundation.org: fix typo] |
| [akpm@linux-foundation.org: document that smart_scan defaults to on] |
| Link: https://lkml.kernel.org/r/20230926040939.516161-4-shr@devkernel.io |
| Signed-off-by: Stefan Roesch <shr@devkernel.io> |
| Reviewed-by: David Hildenbrand <david@redhat.com> |
| Cc: Johannes Weiner <hannes@cmpxchg.org> |
| Cc: Rik van Riel <riel@surriel.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| Documentation/admin-guide/mm/ksm.rst | 9 +++++++++ |
| 1 file changed, 9 insertions(+) |
| |
| --- a/Documentation/admin-guide/mm/ksm.rst~mm-ksm-document-smart-scan-mode |
| +++ a/Documentation/admin-guide/mm/ksm.rst |
| @@ -155,6 +155,15 @@ stable_node_chains_prune_millisecs |
| scan. It's a noop if not a single KSM page hit the |
| ``max_page_sharing`` yet. |
| |
| +smart_scan |
| + Historically KSM checked every candidate page for each scan. It did |
| + not take into account historic information. When smart scan is |
| + enabled, pages that have previously not been de-duplicated get |
| + skipped. How often these pages are skipped depends on how often |
| + de-duplication has already been tried and failed. By default this |
| + optimization is enabled. The ``pages_skipped`` metric shows how |
| + effective the setting is. |
| + |
| The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``: |
| |
| general_profit |
| _ |
