On Tue, May 10, 2022 at 02:16:07PM -0400, Johannes Weiner wrote:
> Hi Minchan,
>
> The patch looks reasonable to me, but one thing stands out:
>
> On Tue, May 10, 2022 at 10:11:00AM -0700, Minchan Kim wrote:
> > @@ -1391,6 +1391,10 @@ static enum page_references folio_check_references(struct folio *folio,
> > if (vm_flags & VM_LOCKED)
> > return PAGEREF_ACTIVATE;
> >
> > + /* page_referenced didn't work due to lock contention */
> > + if (referenced_ptes == -1)
> > + return PAGEREF_KEEP;
> > +
> > if (referenced_ptes) {
> > /*
> > * All mapped folios start out with page table
>
> This means contended inactive pages get rotated.
>
> > @@ -2492,7 +2496,7 @@ static void shrink_active_list(unsigned long nr_to_scan,
> > }
> >
> > if (folio_referenced(folio, 0, sc->target_mem_cgroup,
> > - &vm_flags)) {
> > + &vm_flags) > 0) {
> > /*
> > * Identify referenced, file-backed active pages and
> > * give them one more trip around the active list. So
>
> This means contended active pages do NOT get rotated.
>
> It's a bit of an arbitrary choice what to do with reclaim candidates
> for which you can get no reference information, but staying consistent
> is likely a good idea. My preference would be to just rotate contended
> pages throughout rather than risk dropping the workingset on the floor.
>
> /* Referenced or rmap lock contention: rotate */
> if (folio_referenced() != 0) {
> ...
>
> What do you think?
Sure, it's good start before adding more heuristic later.
Thanks for the review. I will post v4.
