What is the definition of type A and type B Android services?

Question

While inspecting the Total PSS usage by OOM adjustment via dumpsys meminfo oom I came across the categories "A Services" and "B Services".

Do you know what is the exact meaning of these 2 categories?

Maybe it has something to do with the service's position in the LRU?

Answer 1

the following code is used by AMS to manage processes, you can read it to know more.

https://android.googlesource.com/platform/frameworks/base/+/4f868ed/services/core/java/com/android/server/am/ProcessList.java

Put it simple, About 1/3 processes in the service list are A Services, 2/3 are B Services. In some condition, some A services have big PSS will be taken as B Services.

// The B list of SERVICE_ADJ -- these are the old and decrepit
// services that aren't as shiny and interesting as the ones in the A list.
static final int SERVICE_B_ADJ = 8;


if (adj == ProcessList.SERVICE_ADJ) {
if (doingAll) {
    app.serviceb = mNewNumAServiceProcs > (mNumServiceProcs/3);
    mNewNumServiceProcs++;
    if (!app.serviceb) {
        if (mLastMemoryLevel > ProcessStats.ADJ_MEM_FACTOR_NORMAL
                && app.lastPss >= mProcessList.getCachedRestoreThresholdKb()) {
            app.serviceHighRam = true;
            app.serviceb = true;
        } else {
            mNewNumAServiceProcs++;
        }
    } else {
        app.serviceHighRam = false;
    }
}
if (app.serviceb) {
    adj = ProcessList.SERVICE_B_ADJ;
}

}