avoid compiler atom contention

foo.clj

(defn compile-task [^LinkedBlockingDeque deque input-set compiled opts failed]
  (loop [ns-info (.pollFirst deque)]
    (when (and ns-info (not @failed))
      (let [{:keys [requires]} ns-info
            input-set' @input-set]
        (if (every? #(not (contains? input-set' %)) requires)
          (do
            (try
              (let [orig env/*compiler*]
                (binding [env/*compiler* (atom @env/*compiler*)]
                  (swap! compiled conj
                    (-compile (or (:source-file ns-info)
                                (:source-forms ns-info))
                      ; - ns-info -> ns -> cljs file relpath -> js relpath
                      (merge opts
                        {:output-file (comp/rename-to-js
                                        (util/ns->relpath (:ns ns-info)))})))
                  (reset! orig @env/*compiler*)))
              (catch Throwable e
                (util/debug-prn e)
                (reset! failed true)))
            (when-not @failed
              (when-let [ns (:ns ns-info)]
                (swap! input-set disj ns))
              (recur (.pollFirst deque))))
          (do
            (Thread/sleep 10)
            (recur ns-info)))))))