Android: HowTo設定app不被系統kill掉

有一種方法可以設定app永遠不會被kill，AndroidManifest.xml 中添加:android:persistent="true"
適用於放在/system/app下的app 設定後app提升為系統核心層級，任何情況下不會被kill掉, settings->applications裡面也會屏蔽掉stop操作,設定前 Proc #19: adj=svc  /B 4067b028 255:com.xxx.xxx/10001 (started-services)
# cat /proc/255/oom_adj4設定後 PERS #19: adj=core /F 406291f0 155:com.xxx.xxx/10001 (fixed)

# cat /proc/155/oom_adj-12

 

lowmemorykiller的操作規則比如為

write /sys/module/lowmemorykiller/parameters/adj 0,1,2,4,7,15

write /sys/module/lowmemorykiller/parameters/minfree 2048,3072,4096,6144,7168,8192

 

可以看到，設定persistent後， oom_adj=-12，永遠沒有機會被lowmemorykiller處理

 

android:persistent 

Whether or not the application should remain running at all times — "true" if it should, and "false" if not. The default value is "false". Applications should not normally set this flag; persistence mode is intended only for certain system applications

 

代碼

ActivityManagerService.java    final ProcessRecord addAppLocked(ApplicationInfo info) {        ProcessRecord app = getProcessRecordLocked(info.processName, info.uid);        if (app == null) {            app = newProcessRecordLocked(null, info, null);            mProcessNames.put(info.processName, info.uid, app);            updateLruProcessLocked(app, true, true);        }        if ((info.flags&(ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PERSISTENT))                == (ApplicationInfo.FLAG_SYSTEM|ApplicationInfo.FLAG_PERSISTENT)) {            app.persistent = true;            app.maxAdj = CORE_SERVER_ADJ;        }        if (app.thread == null && mPersistentStartingProcesses.indexOf(app) < 0) {            mPersistentStartingProcesses.add(app);            startProcessLocked(app, "added application", app.processName);        }        return app;    }

可以看到同時符合FLAG_SYSTEM(/system/app目錄)及FLAG_PERSISTENT(android:persistent="true")

的app，設定app.maxAdj = CORE_SERVER_ADJ(-12)，而adj=-12不會被lowmemorykiller處理