ZEN: Tune mgLRU to protect cache used in the last second

damentz · intersectRaven · commit c3b33e41465a · 2023-07-01T22:23:05.000+08:00
Although not identical to the le9 patches that protect a byte-amount of cache through tunables, multigenerational LRU now supports protecting cache accessed in the last X milliseconds. In torvalds#218, Yu recommends starting with 1000ms and tuning as needed. This looks like a safe default and turning on this feature should help users that don't know they need it.
diff --git a/mm/vmscan.c b/mm/vmscan.c
@@ -4558,7 +4558,7 @@ static bool lruvec_is_reclaimable(struct lruvec *lruvec, struct scan_control *sc
 }
 
 /* to protect the working set of the last N jiffies */
-static unsigned long lru_gen_min_ttl __read_mostly;
+static unsigned long lru_gen_min_ttl __read_mostly = HZ;
 
 static void lru_gen_age_node(struct pglist_data *pgdat, struct scan_control *sc)
 {

Original file line number	Diff line number	Diff line change
`@@ -4558,7 +4558,7 @@ static bool lruvec_is_reclaimable(struct lruvec lruvec, struct scan_control sc`
`4558`	`4558`	`}`
`4559`	`4559`
`4560`	`4560`	`/* to protect the working set of the last N jiffies */`
`4561`		`-static unsigned long lru_gen_min_ttl __read_mostly;`
	`4561`	`+static unsigned long lru_gen_min_ttl __read_mostly = HZ;`
`4562`	`4562`
`4563`	`4563`	`static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)`
`4564`	`4564`	`{`