Re: [PATCH 3/3] mm: add vmstat statistics for madvise_[cold|pageout]

[Minchan Kim]

On Wed, Jan 18, 2023 at 10:11:46AM +0100, Michal Hocko wrote:
> On Tue 17-01-23 15:16:32, Minchan Kim wrote:
> > madvise LRU manipulation APIs need to scan address ranges to find
> > present pages at page table and provides advice hints for them.
> > 
> > Likewise pg[scan/steal] count on vmstat, madvise_pg[scanned/hinted]
> > shows the proactive reclaim efficiency so this patch addes those
> > two statistics in vmstat.
> 
> Please describe the usecase for those new counters.

I wanted to know the proactive reclaim efficieny using MADV_COLD/MDDV_PAGEOUT.
Userspace has several policy which when/which vmas need to be hinted by the call
and they are evolving. I needed to know how effectively their policy works since
the vma ranges are huge(i.e., nr_hinted/nr_scanned).