simple_lmk: React faster to kswapd reclaim events

With the previous change, there would be up to a KSWAPD_LMK_EXPIRES delay before
Simple LMK would react to a kswapd reclaim being needed, and it would still make
it difficult for a kswapd reclaim to occur if an oom reclaim occurred less than
KSWAPD_LMK_EXPIRES ago.

To remedy Simple LMK's slow kswapd reaction time, poll every other jiffy once
kswapd has been running without sleeping for at least KSWAPD_LMK_EXPIRES' worth
of _wall time_. In addition, when a kswapd reclaim is needed, don't disregard it
if an oom reclaim has occurred recently; in other words, kswapd reclaims are
considered to be of high importance and should not be ignored.

Signed-off-by: Sultan Alsawaf <[email protected]>
Signed-off-by: kdrag0n <[email protected]>

drivers/staging/android/simple_lmk.c

@@ -150,7 +150,7 @@ static cputime_t get_kswapd_cputime(void)
 
 static void simple_lmk_reclaim_work(struct work_struct *work)
 {
-	unsigned long mib_freed = 0;
+	unsigned long mib_freed, resched_delay_jiffies = 1;
 	cputime_t kswapd_time_now;
 	u64 delta_us;
 
@@ -162,15 +162,15 @@ static void simple_lmk_reclaim_work(struct work_struct *work)
 	kswapd_start_time = kswapd_time_now;
 
 	mutex_lock(&reclaim_lock);
-	if (time_after_eq(jiffies, last_reclaim_jiffies + KSWAPD_LMK_EXPIRES))
-		mib_freed = do_lmk_reclaim(MIN_FREE_PAGES);
+	mib_freed = do_lmk_reclaim(MIN_FREE_PAGES);
 	mutex_unlock(&reclaim_lock);
 
 	if (mib_freed)
 		pr_info("kswapd: freed %lu MiB\n", mib_freed);
 
+	resched_delay_jiffies = KSWAPD_LMK_EXPIRES;
 reschedule:
-	queue_delayed_work(simple_lmk_wq, &reclaim_work, KSWAPD_LMK_EXPIRES);
+	queue_delayed_work(simple_lmk_wq, &reclaim_work, resched_delay_jiffies);
 }
 
 void simple_lmk_one_reclaim(void)