diff --git a/actionpack/CHANGELOG b/actionpack/CHANGELOG
index 880f5f6320caa684bd2e1e4799816c40a3b4cbdc..7b0ef65172595d417e219f3e2b975d9c61442571 100644
--- a/actionpack/CHANGELOG
+++ b/actionpack/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Performance: patch cgi/session/pstore to require digest/md5 once rather than per #initialize.  #7583 [Stefan Kaes]
+
 * Undeprecate redirect_to with Hash argument and additional url_for parameters.  #7837 [subelsky]
 
 * Cookie session store: ensure that new sessions doesn't reuse data from a deleted session in the same request.  [Jeremy Kemper]
diff --git a/actionpack/lib/action_controller/cgi_ext/pstore_performance_fix.rb b/actionpack/lib/action_controller/cgi_ext/pstore_performance_fix.rb
new file mode 100644
index 0000000000000000000000000000000000000000..ad08fbe7bf5d39574c52664844554758dd069600
--- /dev/null
+++ b/actionpack/lib/action_controller/cgi_ext/pstore_performance_fix.rb
@@ -0,0 +1,30 @@
+# CGI::Session::Pstore.initialize requires 'digest/md5' on every call.
+# This makes sense when spawning processes per request, but is
+# unnecessarily expensive when serving requests from a long-lived
+# process.
+require 'cgi/session'
+require 'cgi/session/pstore'
+require 'digest/md5'
+
+class CGI::Session::Pstore #:nodoc:
+  def initialize(session, option={})
+    dir = option['tmpdir'] || Dir::tmpdir
+    prefix = option['prefix'] || ''
+    id = session.session_id
+    md5 = Digest::MD5.hexdigest(id)[0,16]
+    path = dir+"/"+prefix+md5
+    path.untaint
+    if File::exist?(path)
+      @hash = nil
+    else
+      unless session.new_session
+        raise CGI::Session::NoSession, "uninitialized session"
+      end
+      @hash = {}
+    end
+    @p = ::PStore.new(path)
+    @p.transaction do |p|
+      File.chmod(0600, p.path)
+    end
+  end
+end
diff --git a/actionpack/lib/action_controller/cgi_process.rb b/actionpack/lib/action_controller/cgi_process.rb
index 5712abc7019dadcf0c61bea7455aa8152ff46755..ddcc6003d0335b6598537866fb8e289f5c5ae640 100644
--- a/actionpack/lib/action_controller/cgi_process.rb
+++ b/actionpack/lib/action_controller/cgi_process.rb
@@ -2,6 +2,7 @@
 require 'action_controller/cgi_ext/cookie_performance_fix'
 require 'action_controller/cgi_ext/raw_post_data_fix'
 require 'action_controller/cgi_ext/session_performance_fix'
+require 'action_controller/cgi_ext/pstore_performance_fix'
 require 'action_controller/session/cookie_store'
 
 module ActionController #:nodoc: