On Fri, Aug 31, 2018 at 05:15:39PM -0400, Rik van Riel wrote:

On Fri, 2018-08-31 at 13:34 -0700, Roman Gushchin wrote:

quoted

diff --git a/mm/vmscan.c b/mm/vmscan.c
index fa2c150ab7b9..c910cf6bf606 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -476,6 +476,10 @@ static unsigned long do_shrink_slab(struct

shrink_control *shrinkctl,
 	delta = freeable >> priority;
 	delta *= 4;
 	do_div(delta, shrinker->seeks);
+
+	if (delta == 0 && freeable > 0)
+		delta = min(freeable, batch_size);
+
 	total_scan += delta;
 	if (total_scan < 0) {
 		pr_err("shrink_slab: %pF negative objects to delete
nr=%ld\n",

I agree that we need to shrink slabs with fewer than
4096 objects, but do we want to put more pressure on
a slab the moment it drops below 4096 than we applied
when it had just over 4096 objects on it?

With this patch, a slab with 5000 objects on it will
get 1 item scanned, while a slab with 4000 objects on
it will see shrinker->batch or SHRINK_BATCH objects
scanned every time.

I don't know if this would cause any issues, just
something to ponder.

Hm, fair enough. So, basically we can always do

    delta = max(delta, min(freeable, batch_size));

Does it look better?

If nobody things this is a problem, you can give the
patch my:

Acked-by: Rik van Riel <riel@surriel.com>

Thanks!