Add some TODO comments for possible poll optimization

src/core/iomgr/pollset_multipoller_with_epoll.c

@@ -180,6 +180,8 @@ static void multipoll_with_epoll_pollset_maybe_work_and_unlock(
   pfds[1].events = POLLIN;
   pfds[1].revents = 0;
 
+  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
+     even going into the blocking annotation if possible */
   GRPC_SCHEDULING_START_BLOCKING_REGION;
   poll_rv = grpc_poll_function(pfds, 2, timeout_ms);
   GRPC_SCHEDULING_END_BLOCKING_REGION;

src/core/iomgr/pollset_multipoller_with_poll_posix.c

@@ -148,6 +148,8 @@ static void multipoll_with_poll_pollset_maybe_work_and_unlock(
                                                POLLOUT, &watchers[i]);
   }
 
+  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
+     even going into the blocking annotation if possible */
   GRPC_SCHEDULING_START_BLOCKING_REGION;
   r = grpc_poll_function(pfds, pfd_count, timeout);
   GRPC_SCHEDULING_END_BLOCKING_REGION;

src/core/iomgr/pollset_posix.c

@@ -467,6 +467,8 @@ static void basic_pollset_maybe_work_and_unlock(grpc_exec_ctx *exec_ctx,
     gpr_mu_unlock(&pollset->mu);
   }
 
+  /* TODO(vpai): Consider first doing a 0 timeout poll here to avoid
+     even going into the blocking annotation if possible */
   /* poll fd count (argument 2) is shortened by one if we have no events
      to poll on - such that it only includes the kicker */
   GRPC_SCHEDULING_START_BLOCKING_REGION;