Are there any reliable performance comparisons between vanilla Drupal 8 versus Drupal 7?
I have searched the web but only find the post "Drupal 7 vs Drupal 8 Performance Comparison", which is far from encouraging.
Drupal Answers is a question and answer site for Drupal developers and administrators. It only takes a minute to sign up.Sign up to join this community
No, there is no reliable comparison, because doing that is almost impossible. There are various reasons for that, one is that D8 vanilla is like D7 vanilla + a whole bunch of modules, especially views.
If you compare a single request on a vanilla installation, then D8 is clearly slower than D7 (even if you add views), quite a bit actually. That might still improve more or less until the release, but it's not going turn around completely.
D8 is just running a lot more code, our own and vendor code like symfony underneath, so that takes more time. The service container also adds quite a bit of overhead.
However, D8 has a number of things that are hopefully going to make more than up for that on real sites
Also keep in mind, if you care about performance, then you're very likely not running vanilla D7/D8 sites, you have large sites with a lot of content. And as mentioned above, D8 brings a lot of tools to help you to make those kind of sites faster. Some things will require work as a developer and need to be done right (just like in D7), but if you do, then I think that D8 can perform pretty well in real world scenarios.
There are a bunch of patches for D8 that should land before it is released. This presentation at the 2015 LA DrupalCon should explain what is happening to make sure D8 is fast.
See here for an example of one of the patches that
is being worked on right now was committed.
See the issue queue for most of the open issues in terms of D8 performance improvements.