On 30.12.22 02:15, yang.yang29@xxxxxxxxxx wrote:
From: xu xin <xu.xin16@xxxxxxxxxx> As pages_sharing and pages_shared don't include the number of zero pages merged by KSM, 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. In the early days of use_zero_pages, zero-pages was unable to get unshared by the ways like MADV_UNMERGEABLE so it's hard to count how many times one of those zeropages was then unmerged. But now, unsharing KSM-placed zero page accurately has been achieved, so we can easily count both how many times a page full of zeroes was merged with zero-page and how many times one of those pages was then unmerged. and so, it helps to estimate memory demands when each and every shared page could get unshared. So we add zero_pages_sharing under /sys/kernel/mm/ksm/ to show the number of all zero pages placed by KSM. Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx> Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Xuexin Jiang <jiang.xuexin@xxxxxxxxxx> Reviewed-by: Xiaokai Ran <ran.xiaokai@xxxxxxxxxx> Reviewed-by: Yang Yang <yang.yang29@xxxxxxxxxx> v4->v5: fix warning mm/ksm.c:3238:9: warning: no previous prototype for 'zero_pages_sharing_show' [-Wmissing-prototypes]. --- mm/ksm.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index 652c088f9786..72c0722be280 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -276,6 +276,9 @@ static unsigned int zero_checksum __read_mostly; /* Whether to merge empty (zeroed) pages with actual zero pages */ static bool ksm_use_zero_pages __read_mostly; +/* The number of zero pages placed by KSM use_zero_pages */ +static unsigned long ksm_zero_pages_sharing;
Does this count how many zero pages are currently placed or how many rmap items with ZERO_PAGE_FLAG are in the system?
IOW, if someone triggers MADV_DONTNEED on such a zeropage, the counter will not get updated, correct?
-- Thanks, David / dhildenb
