LRU maint test fix for second mystery

If an LRU is too large, ACTIVE processing was elided on purpose. However it's
very easy for even moderate write pressure to pass a large number of ACTIVE
items into COLD. This combined with not removing items from COLD immediately
(fixed in another commit) could easily cause very active items to be evicted
along with inactive ones.

With the speedup of the processing thread (with some low-fruit still), it
should be fine to quickly flip items in place.

This opens up a problem under extreme write pressure which overwhelms the
background thread, or extreme re-scanning of large numbers of items.

It might still be valuable to do pressure release or direct reclaim pulling if
COLD gets too large. Performance tests should be done to find the threshold
and experiment.

1 files changed, 8 insertions, 8 deletions

diff --git a/items.c b/items.c
index 0264c32..d3d240f 100644
--- a/items.c
+++ b/items.c
@@ -958,20 +958,20 @@ static int lru_pull_tail(const int orig_id, const int cur_lru,
             case WARM_LRU:
                 if (limit == 0)
                     limit = total_bytes * settings.warm_lru_pct / 100;
-                if (sizes_bytes[id] > limit) {
+                /* Rescue ACTIVE items aggressively */
+                if ((search->it_flags & ITEM_ACTIVE) != 0) {
+                    itemstats[id].moves_within_lru++;
+                    search->it_flags &= ~ITEM_ACTIVE;
+                    do_item_update_nolock(search);
+                    do_item_remove(search);
+                    item_trylock_unlock(hold_lock);
+                } else if (sizes_bytes[id] > limit) {
                     itemstats[id].moves_to_cold++;
                     move_to_lru = COLD_LRU;
                     do_item_unlink_q(search);
                     it = search;
                     removed++;
                     break;
-                } else if ((search->it_flags & ITEM_ACTIVE) != 0) {
-                    /* Only allow ACTIVE relinking if we're not too large. */
-                    itemstats[id].moves_within_lru++;
-                    search->it_flags &= ~ITEM_ACTIVE;
-                    do_item_update_nolock(search);
-                    do_item_remove(search);
-                    item_trylock_unlock(hold_lock);
                 } else {
                     /* Don't want to move to COLD, not active, bail out */
                     it = search;