【代码】Android: 怎样设置app不被系统k掉

有一种方法可以设置app永远不会被kill，AndroidManifest.xml 中添加:

android:persistent="true"

适用于放在/system/app下的app

设置后app提升为系统核心级别，任何情况下不会被kill掉, settings->applications里面也会屏蔽掉stop操作,
设置前 Proc #19: adj=svc /B 4067b028 255:com.xxx.xxx/10001 (started-services)
# cat /proc/255/oom_adj
4
设置后 PERS #19: adj=core /F 406291f0 155:com.xxx.xxx/10001 (fixed)
# cat /proc/155/oom_adj
-12

lowmemorykiller的操作规则比如为
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，设置persistent后， oom_adj=-12，永远没有机会被lowmemorykiller处理

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

代码

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;    }

可以看到同时符合FLAG_SYSTEM(/system/app目录)及FLAG_PERSISTENT(android:persistent="true")

的app，设置app.maxAdj = CORE_SERVER_ADJ(-12)，而adj=-12不会被lowmemorykiller处理

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