【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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