a71-common: Enable zram writeback

Bug: 128889899
Test: Boot to home

Change-Id: I48ae06e54a66a7d6965afbe8db3d2f157cf8a1f4

init/fstab.qcom

@@ -61,4 +61,4 @@ odm	/odm	ext4	ro	wait,logical,first_stage_mount,readahead_size_kb=128
 /devices/platform/soc/a600000.ssusb/a600000.dwc3/xhci-hcd.0.auto*       auto                auto    defaults        voldmanaged=usb:auto
 
 # ZRAM
-/dev/block/zram0                                        none                    swap    defaults        zramsize=50%
+/dev/block/zram0                                        none                    swap    defaults        zramsize=50%,zram_loopback_path=/data/unencrypted/zram_swap,zram_loopback_size=512M

overlay/frameworks/base/core/res/res/values/config.xml

@@ -1469,4 +1469,7 @@
         <item>mobile_foc,30,0,2,-1,true</item>
         <item>mobile_rcs,31,0,2,-1,true</item>
     </string-array>
+
+    <!-- Enable Zram writeback feature to allow unused pages in zram be written to flash. -->
+    <bool name="config_zramWriteback">true</bool>
 </resources>

vendor.prop

@@ -277,5 +277,10 @@ ro.vendor.vibrator_hal.tick_duration=40
 # WiFi
 wifi.aware.interface=wifi-aware0
 
+# Zram
+ro.zram.first_wb_delay_mins=180
+ro.zram.mark_idle_delay_mins=60
+ro.zram.periodic_wb_delay_hours=24
+
 # Zygote
 zygote.critical_window.minute=10