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?
