ActivityManager.java

/**
     * Returns true if this is a low-RAM device.  Exactly whether a device is low-RAM
     * is ultimately up to the device configuration, but currently it generally means
     * something with 1GB or less of RAM.  This is mostly intended to be used by apps
     * to determine whether they should turn off certain features that require more RAM.
     */
    public boolean isLowRamDevice() {
        return isLowRamDeviceStatic();
    }

    /** @hide */
    public static boolean isLowRamDeviceStatic() {
        return RoSystemProperties.CONFIG_LOW_RAM ||
                (Build.IS_DEBUGGABLE && DEVELOPMENT_FORCE_LOW_RAM);
    }

读取的系统属性：

public static final boolean CONFIG_LOW_RAM =
            SystemProperties.getBoolean("ro.config.low_ram", false);

package com.android.internal.os;

import android.os.SystemProperties;

/**
 * This is a cache of various ro.* properties so that they can be read just once
 * at class init time.
 */
public class RoSystemProperties {
    public static final boolean DEBUGGABLE =
            SystemProperties.getInt("ro.debuggable", 0) == 1;
    public static final int FACTORYTEST =
            SystemProperties.getInt("ro.factorytest", 0);
    public static final String CONTROL_PRIVAPP_PERMISSIONS =
            SystemProperties.get("ro.control_privapp_permissions");

    // ------ ro.config.* -------- //
    public static final boolean CONFIG_AVOID_GFX_ACCEL =
            SystemProperties.getBoolean("ro.config.avoid_gfx_accel", false);
    public static final boolean CONFIG_LOW_RAM =
            SystemProperties.getBoolean("ro.config.low_ram", false);
    public static final boolean CONFIG_SMALL_BATTERY =
            SystemProperties.getBoolean("ro.config.small_battery", false);

    // ------ ro.fw.* ------------ //
    public static final boolean FW_SYSTEM_USER_SPLIT =
            SystemProperties.getBoolean("ro.fw.system_user_split", false);

    // ------ ro.crypto.* -------- //
    public static final String CRYPTO_STATE = SystemProperties.get("ro.crypto.state");
    public static final String CRYPTO_TYPE = SystemProperties.get("ro.crypto.type");
    // These are pseudo-properties
    public static final boolean CRYPTO_ENCRYPTABLE =
            !CRYPTO_STATE.isEmpty() && !"unsupported".equals(CRYPTO_STATE);
    public static final boolean CRYPTO_ENCRYPTED =
            "encrypted".equalsIgnoreCase(CRYPTO_STATE);
    public static final boolean CRYPTO_FILE_ENCRYPTED =
            "file".equalsIgnoreCase(CRYPTO_TYPE);
    public static final boolean CRYPTO_BLOCK_ENCRYPTED =
            "block".equalsIgnoreCase(CRYPTO_TYPE);

    public static final boolean CONTROL_PRIVAPP_PERMISSIONS_LOG =
            "log".equalsIgnoreCase(CONTROL_PRIVAPP_PERMISSIONS);
    public static final boolean CONTROL_PRIVAPP_PERMISSIONS_ENFORCE =
            "enforce".equalsIgnoreCase(CONTROL_PRIVAPP_PERMISSIONS);
    public static final boolean CONTROL_PRIVAPP_PERMISSIONS_DISABLE =
            !CONTROL_PRIVAPP_PERMISSIONS_LOG && !CONTROL_PRIVAPP_PERMISSIONS_ENFORCE;

}