VARNISH CONFIGURATION

I have installed Varnish on CWPpro version: 0.9.8.1129, Web Servers: nginx-varnish-apache.

Now how can I configure the maximum amount of memory Varnish can use? I did some research but none of those config files mentioned contain memory allocation.

/etc/varnish/conf.d/vhosts/mydomain.conf   for example  has no options for memory allocation

How can I see the cached files, or at least the top cached files?

Thanks

I think I found the config file /usr/lib/systemd/system/varnish.service
and the default value -s malloc,256m   can be replaced to change the allocated memory size

Could not find out how can I see the cached files?