Messages in this thread | | | Date | Wed, 18 Jan 2023 15:30:18 +0100 | Subject | Re: [PATCH v5 3/6] ksm: count all zero pages placed by KSM | From | David Hildenbrand <> |
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On 30.12.22 02:15, yang.yang29@zte.com.cn wrote: > From: xu xin <xu.xin16@zte.com.cn> > > 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@zte.com.cn> > Cc: Claudio Imbrenda <imbrenda@linux.ibm.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Xuexin Jiang <jiang.xuexin@zte.com.cn> > Reviewed-by: Xiaokai Ran <ran.xiaokai@zte.com.cn> > Reviewed-by: Yang Yang <yang.yang29@zte.com.cn> > > 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
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