post_boot: Ensure SLAB_STORE_USER is disabled for zram kmem_caches

ZRAM compression uses the linux slub allocator its internal data
structures. If these internal data structure consume a lot of memory,
ZRAM compression may increase memory usage, rather than decrease it
as expected. Decrease the chance of this occuring by ensuring the
SLAB_STORE_USER debug option is disabled.

Change-Id: I4684feda94b7bebacb6218b7f979c95771b0ee10
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>

rootdir/bin/init.qcom.post_boot.sh

@@ -392,6 +392,16 @@ function configure_zram_parameters() {
         else
             echo $zRamSizeBytes > /sys/block/zram0/disksize
         fi
+
+        # ZRAM may use more memory than it saves if SLAB_STORE_USER
+        # debug option is enabled.
+        if [ -e /sys/kernel/slab/zs_handle ]; then
+            echo 0 > /sys/kernel/slab/zs_handle/store_user
+        fi
+        if [ -e /sys/kernel/slab/zspage ]; then
+            echo 0 > /sys/kernel/slab/zspage/store_user
+        fi
+
         mkswap /dev/block/zram0
         swapon /dev/block/zram0 -p 32758
     fi