Buffers reuse in chunked filter. There were 2 buffers allocated on each buffer chain sent through chunked filter (one buffer for chunk size, another one for trailing CRLF, about 120 bytes in total on 32-bit platforms). This resulted in large memory consumption with long-lived requests sending many buffer chains. Usual example of problematic scenario is streaming though proxy with proxy_buffering set to off. Introduced buffers reuse reduces memory consumption in the above problematic scenario. See here for initial report: http://mailman.nginx.org/pipermail/nginx/2010-April/019814.html

uwsgi_param  QUERY_STRING       $query_string;
uwsgi_param  REQUEST_METHOD     $request_method;
uwsgi_param  CONTENT_TYPE       $content_type;
uwsgi_param  CONTENT_LENGTH     $content_length;

uwsgi_param  REQUEST_URI        $request_uri;
uwsgi_param  PATH_INFO          $document_uri;
uwsgi_param  DOCUMENT_ROOT      $document_root;
uwsgi_param  SERVER_PROTOCOL    $server_protocol;

uwsgi_param  REMOTE_ADDR        $remote_addr;
uwsgi_param  REMOTE_PORT        $remote_port;
uwsgi_param  SERVER_PORT        $server_port;
uwsgi_param  SERVER_NAME        $server_name;