commit 26614d0076ed87a5306cd256241de7f387d99eec
author Suren Baghdasaryan <surenb@google.com> Thu Sep 19 15:27:21 2019 -0700
committer Suren Baghdasaryan <surenb@google.com> Mon Sep 30 16:54:55 2019 +0000
tree 2dde0470d724ddd615be87e55bc632535e120675
parent 8e4d12838bb90ba1f1c51b1178755e87e40296a0

lmkd: Prevent killing foreground processes due to thrashing

Page cache thrashing affects device performance and by killing a process
we try to stop it. However if the thrashing application is the one which
user is interacting with then lmkd should not kill it even though it might
affect device performance.

Bug: 141286980
Test: SequentialRWTest CTS test
Change-Id: If86c0e7e8ad9adf1816659562151ca083eaa65c4
Signed-off-by: Suren Baghdasaryan <surenb@google.com>

lmkd/lmkd.c

diff --git a/lmkd/lmkd.c b/lmkd/lmkd.c
index b9a7366..2ba3f44 100644
--- a/lmkd/lmkd.c
+++ b/lmkd/lmkd.c
@@ -83,6 +83,8 @@
 #define PROC_STATUS_TGID_FIELD "Tgid:"
 #define LINE_MAX 128
 
+#define PERCEPTIBLE_APP_ADJ 200
+
 /* Android Logger event logtags (see event.logtags) */
 #define MEMINFO_LOG_TAG 10195355
 
@@ -2046,6 +2048,8 @@
     enum reclaim_state reclaim = NO_RECLAIM;
     enum zone_watermark wmark = WMARK_NONE;
     char kill_desc[LINE_MAX];
+    bool cut_thrashing_limit = false;
+    int min_score_adj = 0;
 
     /* Skip while still killing a process */
     if (is_kill_pending()) {
@@ -2164,22 +2168,35 @@
             mi.field.free_swap * page_k, swap_low_threshold * page_k);
     } else if (wmark < WMARK_HIGH && thrashing > thrashing_limit) {
         /* Page cache is thrashing while memory is low */
-        thrashing_limit = (thrashing_limit * (100 - thrashing_limit_decay_pct)) / 100;
         kill_reason = LOW_MEM_AND_THRASHING;
         snprintf(kill_desc, sizeof(kill_desc), "%s watermark is breached and thrashing (%"
             PRId64 "%%)", wmark > WMARK_LOW ? "min" : "low", thrashing);
+        cut_thrashing_limit = true;
+        /* Do not kill perceptible apps because of thrashing */
+        min_score_adj = PERCEPTIBLE_APP_ADJ;
     } else if (reclaim == DIRECT_RECLAIM && thrashing > thrashing_limit) {
         /* Page cache is thrashing while in direct reclaim (mostly happens on lowram devices) */
-        thrashing_limit = (thrashing_limit * (100 - thrashing_limit_decay_pct)) / 100;
         kill_reason = DIRECT_RECL_AND_THRASHING;
         snprintf(kill_desc, sizeof(kill_desc), "device is in direct reclaim and thrashing (%"
             PRId64 "%%)", thrashing);
+        cut_thrashing_limit = true;
+        /* Do not kill perceptible apps because of thrashing */
+        min_score_adj = PERCEPTIBLE_APP_ADJ;
     }
 
     /* Kill a process if necessary */
     if (kill_reason != NONE) {
-        int pages_freed = find_and_kill_process(0, kill_desc);
-        killing = (pages_freed > 0);
+        int pages_freed = find_and_kill_process(min_score_adj, kill_desc);
+        if (pages_freed > 0) {
+            killing = true;
+            if (cut_thrashing_limit) {
+                /*
+                 * Cut thrasing limit by thrashing_limit_decay_pct percentage of the current
+                 * thrashing limit until the system stops thrashing.
+                 */
+                thrashing_limit = (thrashing_limit * (100 - thrashing_limit_decay_pct)) / 100;
+            }
+        }
         meminfo_log(&mi);
     }