Manually compact GC before fork

.travis.yml

@@ -52,6 +52,7 @@ matrix:
     - rvm: ruby-head
       env: jit=yes
     - rvm: truffleruby
+    - rvm: 2.7.0-preview3
 
   allow_failures:
     - rvm: jruby-9.2.9.0

History.md

@@ -4,6 +4,7 @@
   * Add pumactl `thread-backtraces` command to print thread backtraces (#2053)
   * Configuration: `environment` is read from `RAILS_ENV`, if `RACK_ENV` can't be found (#2022)
   * `Puma.stats` now returns a Hash instead of a JSON string (#2086)
+  * `GC.compact` is called before fork if available (#2093)
 
 * Bugfixes
   * Your bugfix goes here (#Github Number)

lib/puma/cluster.rb

@@ -486,6 +486,7 @@ def run
       @master_read, @worker_write = read, @wakeup
 
       @launcher.config.run_hooks :before_fork, nil
+      GC.compact if GC.respond_to?(:compact)
 
       spawn_workers