Got overhead down from 127 to 85. All tests pass:

  * Tentatively replaced HeaderHash with SimpleHeaderHash, which does not preserve
    case but does handle converting Arrays to Strings in to_hash. This requires
    further discussion.
  * Moved default_charset to ActionDispatch::Response to avoid having to hop over
    to ActionController. Ideally, this would be a constant on AD::Response, but
    some tests expect to be able to change it dynamically and I didn't want to change
    them yet.
  * Completely override #initialize from Rack::Response. Previously, it was creating
    a HeaderHash, and then we were creating an entirely new one. There is no way to
    call super without incurring the overhead of creating a HeaderHash.
  * Override #write from Rack::Response. Its implementation tracks Content-Length,
    and doing so adds additional overhead that could be mooted if other middleware
    changes the body. It is more efficiently done at the top-level server.
  * Change sending_file to an instance_variable instead of header inspection. In
    general, if a state is important, it should be set as a property of the response
    not reconstructed later.
  * Set the Etag to @body instead of .body. AS::Cache.expand_cache_key handles
    Arrays fine, and it's more efficient to let it handle the body parts, since
    it is not forced to create a joined String.
  * If we detect the default cache control case, just set it, rather than setting
    the constituent parts and then running the normal (expensive) code to generate
    the string.

1 files changed, 2 insertions, 1 deletions

diff --git a/actionpack/lib/action_controller/metal/streaming.rb b/actionpack/lib/action_controller/metal/streaming.rb
index 57318e8747..4761763a26 100644
--- a/actionpack/lib/action_controller/metal/streaming.rb
+++ b/actionpack/lib/action_controller/metal/streaming.rb
@@ -145,7 +145,6 @@ module ActionController #:nodoc:
       def send_data(data, options = {}) #:doc:
         logger.info "Sending data #{options[:filename]}" if logger
         send_file_headers! options.merge(:length => data.bytesize)
-        @performed_render = false
         render :status => options[:status], :text => data
       end
 
@@ -175,6 +174,8 @@ module ActionController #:nodoc:
           'Content-Transfer-Encoding' => 'binary'
         )
 
+        response.sending_file = true
+
         # Fix a problem with IE 6.0 on opening downloaded files:
         # If Cache-Control: no-cache is set (which Rails does by default),
         # IE removes the file it just downloaded from its cache immediately