Messages in this thread | | | Date | Thu, 29 Sep 2022 11:21:44 +0200 | From | David Hildenbrand <> | Subject | Re: [PATCH 0/3] ksm: fix incorrect count of merged pages when enabling use_zero_pages |
| |
On 29.09.22 04:52, xu.xin.sc@gmail.com wrote: > From: xu xin <xu.xin16@zte.com.cn> > > Before enabling use_zero_pages by setting /sys/kernel/mm/ksm/ > use_zero_pages to 1, pages_sharing of KSM is basically accurate. But > after enabling use_zero_pages, all empty pages that are merged with > kernel zero page are not counted in pages_sharing or pages_shared. > That is because the rmap_items of these ksm zero pages are not > appended to The Stable Tree of KSM. > > We need to add the count of empty pages to let users know how many empty > pages are merged with kernel zero page(s). > > Please see the subsequent patches for details.
Just raising the topic here because it's related to the KSM usage of the shared zero-page:
MADV_UNMERGEABLE and other ways to trigger unsharing will *not* unshare the shared zeropage as placed by KSM (which is against the MADV_UNMERGEABLE documentation at least). It will only unshare actual KSM pages. We might not want want to blindly unshare all shared zeropages in applicable VMAs ... using a dedicated shared zero (KSM) page -- instead of the generic zero page -- might be one way to handle this cleaner.
Would that also fix some of the issues you describe above?
-- Thanks,
David / dhildenb
| |