From: xu xin <xu.xin16@xxxxxxxxxx> The core idea of this patch set is to enable users to perceive the number of any pages merged by KSM, regardless of whether use_zero_page switch has been turned on, so that users can know how much free memory increase is really due to their madvise(MERGEABLE) actions. But the problem is, when enabling use_zero_pages, all empty pages will be merged with kernel zero pages instead of with each other as use_zero_pages is disabled, and then these zero-pages are no longer monitored by KSM. The motivations to do this is seen at: https://lore.kernel.org/lkml/202302100915227721315@xxxxxxxxxx/ In one word, we hope to implement the support for KSM-placed zero pages tracking without affecting the feature of use_zero_pages, so that app developer can also benefit from knowing the actual KSM profit by getting KSM-placed zero pages to optimize applications eventually when /sys/kernel/mm/ksm/use_zero_pages is enabled. Change log ---------- v7->v8: (1) Since [1] which fix the bug of pte_mkdirty on sparc64 that makes pte writable, then we can remove the architechture restrictions of our features. (2) Improve the scheme of update ksm_zero_pages: add the handling case when khugepaged replaces a shared zeropage by a THP. [1] https://lore.kernel.org/all/20230411141529.428991-2-david@xxxxxxxxxx/ v6->v7: This is an all-newed version which is different from v6 which relys on KSM's rmap_item. The patch series don't rely on rmap_item but pte_dirty, so the general handling of tracking KSM-placed zero-pages is simplified a lot. For safety, we restrict this feature only to the tested and known-working architechtures (ARM, ARM64, and X86) fow now. xu xin (6): ksm: support unsharing KSM-placed zero pages ksm: count all zero pages placed by KSM ksm: add ksm zero pages for each process ksm: add documentation for ksm zero pages ksm: update the calculation of KSM profit selftest: add a testcase of ksm zero pages Documentation/admin-guide/mm/ksm.rst | 26 +++++--- fs/proc/base.c | 1 + include/linux/ksm.h | 25 ++++++++ include/linux/mm_types.h | 9 ++- mm/khugepaged.c | 3 + mm/ksm.c | 19 +++++- mm/memory.c | 7 ++- tools/testing/selftests/mm/ksm_functional_tests.c | 75 +++++++++++++++++++++++ 8 files changed, 152 insertions(+), 13 deletions(-) -- 2.15.2
