Re: [PATCH v2 1/4] mm/vmscan: fix anon-only reclaim evicting file pages when swappiness=max
From: Ridong Chen
Date: Wed Jul 22 2026 - 22:00:33 EST
On 7/21/2026 3:45 PM, Barry Song wrote:
On Mon, Jul 20, 2026 at 12:43 PM Ridong Chen <ridong.chen@xxxxxxxxx> wrote:Eh, shrink_node handles MGLRU global reclaim via a special branch, so we'd have to add the warning at the beginning of shrink_node, but that feels a bit jarring. Let's just go with adding some comments instead.
[...]
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2501,6 +2501,17 @@ static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc,
enum scan_balance scan_balance;
enum lru_list lru;
+ /* Proactive reclaim initiated by userspace for anonymous memory only */
+ if (swappiness == SWAPPINESS_ANON_ONLY) {
+ WARN_ON_ONCE(!sc->proactive);
I feel it's a bit odd that the WARN_ON_ONCE() is placed here. Maybe
adding a short comment would make the intent clearer. For example:
"SWAPPINESS_ANON_ONLY is only allowed for proactive reclaim."
Hi Barry,
I didn't change the original logic in this patch. I agree that adding a
comment would help clarify the intent.
I'll include that in the next version.
I'm not sure whether it would be better to issue this warning earlier,
for example in try_to_free_mem_cgroup_pages(). That said, I don't
feel strongly about this.
Since patch 4 will address the MGLRU issue and could also include this
warning, I think that triggering the warning earlier makes sense and
would be more general. Would it be acceptable to add a separate patch
(e.g., patch 5) for moving the warning? That way, each patch stays
focused on a single logical change.
I'm not quite sure where the best place would be to move it earlier. We
already have two places that perform proactive reclaim:
try_to_free_mem_cgroup_pages() and __node_reclaim(). There are also
other reclaim paths that are not proactive. Since they all eventually call
shrink_node(), would it make more sense to handle it there?
If we can't find a suitable common path, I guess simply adding some comments
to the current patches would be good enough.
--
Best regards
Ridong