admin-guide/mm/ksm.rst

8 KSM is a memory-saving de-duplication feature, enabled by CONFIG_KSM=y,
19 content which can be replaced by a single write-protected page (which
47 may suddenly require more memory than is available - possibly failing
48 with EAGAIN, but more probably arousing the Out-Of-Memory killer.
60 will exceed ``vm.max_map_count`` (see Documentation/admin-guide/sysctl/vm.rst).
69 of processing power: some installations will disable KSM for that reason.
84         been set to scan-time.
151         traversals are always schedule friendly themselves.
164         enabled, pages that have previously not been de-duplicated get
166         de-duplication has already been tried and failed. By default this
172         supported: none and scan-time. The default is none. By setting
173         ``advisor_mode`` to scan-time, the scan time advisor is enabled.
242 1) How to determine whether KSM save memory or consume memory in system-wide
245 	general_profit =~ ksm_saved_pages * sizeof(page) - (all_rmap_items) *
256 	process_profit =~ ksm_saved_pages * sizeof(page) -
266 ``ksm_merging_pages`` means a bad madvise-applied policy, so developers or
269 separately 32B on 32-bit CPU architecture and 64B on 64-bit CPU architecture.
270 so if the ``ksm_rmap_items/ksm_merging_pages`` ratio exceeds 64 on 64-bit CPU
271 or exceeds 128 on 32-bit CPU, then the app's madvise policy should be dropped,
290 	cannot do all the locking needed to reconstitute a cross-anon_vma KSM page.
303 scan-time. With none, no advisor is enabled. The default is none.
318 The ``pages_to_scan`` parameter is re-calculated after a scan has been completed.
321 --