Recently I've installed the version 201704 of alfresco community and comparing to 5.0.d version, the new one is considerable slower than the old one. I did a new config to JVM (JAVA_OPTS="$JAVA_OPTS -Xmx3G") as suggested but it still too slow. Just to open the menu "Admin tools" it's taking between 10 and 12 seconds in the new version, while the old version takes only 3 seconds or less.
I'm using a Linux 64 bits AWS instance, 2 vCPU and 8Gb RAM.
Agree with Markus, CPU is one of the key factors, especially if you don't have SOLR in a separate server or if you are running your database locally. IO may be another factor, if your (local) hard disk is pretty slow (cheap), when SOLR, database and Alfresco repo are competing for IO resources in the same disk. The only thing that it is still quite surprising is that difference between two "close" Alfresco versions.