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

damentz · Kaz205 · commit e062b6a938b4 · 2022-05-30T16:55:02.000+09:00
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
@@ -4382,7 +4382,7 @@ static bool age_lruvec(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
`@@ -4382,7 +4382,7 @@ static bool age_lruvec(struct lruvec lruvec, struct scan_control sc,`
`4382`	`4382`	`}`
`4383`	`4383`
`4384`	`4384`	`/* to protect the working set of the last N jiffies */`
`4385`		`-static unsigned long lru_gen_min_ttl __read_mostly;`
	`4385`	`+static unsigned long lru_gen_min_ttl __read_mostly = HZ;`
`4386`	`4386`
`4387`	`4387`	`static void lru_gen_age_node(struct pglist_data pgdat, struct scan_control sc)`
`4388`	`4388`	`{`