From: xu xin <xu.xin16@xxxxxxxxxx> Before enabling use_zero_pages by setting /sys/kernel/mm/ksm/ use_zero_pages to 1, pages_sharing of KSM is basically accurate. But when 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 these empty pages are merged with zero-pages then no longer managed by KSM, which leads to two issues at least: 1) 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); see the link: https://lore.kernel.org/lkml/4a3daba6-18f9-d252-697c-197f65578c44@xxxxxxxxxx/ 2) we cannot know how many pages are zero pages placed by KSM when enabling use_zero_pages, which leads to KSM not being transparent with all actual merged pages by KSM. With the patch series, we can unshare zero-pages(KSM-placed) accurately and count ksm zero pages. --- v1->v2: [patch 4/5] fix build warning, mm/ksm.c:550, misleading indentation; statement 'rmap_item->mm->ksm_zero_pages_sharing--;' is not part of the previous 'if'. *** BLURB HERE *** xu xin (5): ksm: abstract the function try_to_get_old_rmap_item ksm: support unsharing zero pages placed by KSM ksm: count all zero pages placed by KSM ksm: count zero pages for each process ksm: add zero_pages_sharing documentation Documentation/admin-guide/mm/ksm.rst | 10 +- fs/proc/base.c | 1 + include/linux/mm_types.h | 7 +- mm/ksm.c | 177 +++++++++++++++++++++------ 4 files changed, 157 insertions(+), 38 deletions(-) -- 2.25.1
