lmkd: Do not set soft_limit_in_bytes on high-end devices

Setting memory.soft_limit_in_bytes on high-end devices with large memory
reserves affects performance of memory-hungry applications that have
large workingsets and keep thrashing because of the memory limits imposed.
Limit the usage of memory.soft_limit_in_bytes to low-memory devices only.
Add debug messages for future troubleshooting to capture cases when
vmpressure events are being ignored.

Bug: 78916015
Test: collect vmstat while running a heavy app
Change-Id: Ib4434b96d2be802ef89960b573486eae8d12f198
Merged-In: Ib4434b96d2be802ef89960b573486eae8d12f198
Signed-off-by: Suren Baghdasaryan <surenb@google.com>

lmkd/lmkd.c

@@ -459,6 +459,7 @@ static void cmd_procprio(LMKD_CTRL_PACKET packet) {
     if (use_inkernel_interface)
         return;
 
+    if (low_ram_device) {
         if (params.oomadj >= 900) {
             soft_limit_mult = 0;
         } else if (params.oomadj >= 800) {
@@ -492,6 +493,7 @@ static void cmd_procprio(LMKD_CTRL_PACKET packet) {
              params.uid, params.pid);
         snprintf(val, sizeof(val), "%d", soft_limit_mult * EIGHT_MEGA);
         writefilestring(path, val);
+    }
 
     procp = pid_lookup(params.pid);
     if (!procp) {
@@ -1214,8 +1216,15 @@ static void mp_event_common(int data, uint32_t events __unused) {
             }
         }
 
-        if (min_score_adj == OOM_SCORE_ADJ_MAX + 1)
+        if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
+            if (debug_process_killing) {
+                ALOGI("Ignore %s memory pressure event "
+                      "(free memory=%ldkB, cache=%ldkB, limit=%ldkB)",
+                      level_name[level], other_free * page_k, other_file * page_k,
+                      (long)lowmem_minfree[lowmem_targets_size - 1] * page_k);
+            }
             return;
+        }
 
         /* Free up enough pages to push over the highest minfree level */
         pages_to_free = lowmem_minfree[lowmem_targets_size - 1] -