sudo a2enmod deflate

sudo nano /etc/apache2/conf.d/deflate.conf

<IfModule mod_deflate.c>
   DeflateCompressionLevel 6
   AddOutputFilterByType DEFLATE text/plain
   AddOutputFilterByType DEFLATE text/html
   AddOutputFilterByType DEFLATE text/xml
   AddOutputFilterByType DEFLATE text/css
   AddOutputFilterByType DEFLATE application/xhtml+xml
   AddOutputFilterByType DEFLATE application/xml

Step 1 :

Check if AppArmor is enabled or not. And make sure MySQL profile is enabled too.

sudo apparmor_status

Step 2 :

Create a profile of Apache2.

sudo aa-genprof apache2

sudo nano /etc/apparmor.d/usr.sbin.apache2

Add the following lines within ^DEFAULT_URI bracket.