Reduce contention on lock

Change the fd watcher from being O(active_pollers) to O(1), reducing time spent under the fd->watcher_mu lock, and ultimately scaling us much better.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/core/iomgr/pollset_posix.c b/src/core/iomgr/pollset_posix.c
index b1c2c64a18..b0404b870b 100644
--- a/src/core/iomgr/pollset_posix.c
+++ b/src/core/iomgr/pollset_posix.c
@@ -80,7 +80,9 @@ void grpc_pollset_kick(grpc_pollset *p) {
   }
 }
 
-void grpc_pollset_force_kick(grpc_pollset *p) { grpc_pollset_kick_kick(&p->kick_state); }
+void grpc_pollset_force_kick(grpc_pollset *p) {
+  grpc_pollset_kick_kick(&p->kick_state);
+}
 
 /* global state management */
 
@@ -217,6 +219,7 @@ static int unary_poll_pollset_maybe_work(grpc_pollset *pollset,
                                          int allow_synchronous_callback) {
   struct pollfd pfd[2];
   grpc_fd *fd;
+  grpc_fd_watcher fd_watcher;
   int timeout;
   int r;
 
@@ -249,7 +252,7 @@ static int unary_poll_pollset_maybe_work(grpc_pollset *pollset,
   pollset->counter = 1;
   gpr_mu_unlock(&pollset->mu);
 
-  pfd[1].events = grpc_fd_begin_poll(fd, pollset, POLLIN, POLLOUT);
+  pfd[1].events = grpc_fd_begin_poll(fd, pollset, POLLIN, POLLOUT, &fd_watcher);
 
   r = poll(pfd, GPR_ARRAY_SIZE(pfd), timeout);
   if (r < 0) {
@@ -271,7 +274,7 @@ static int unary_poll_pollset_maybe_work(grpc_pollset *pollset,
   }
 
   grpc_pollset_kick_post_poll(&pollset->kick_state);
-  grpc_fd_end_poll(fd, pollset);
+  grpc_fd_end_poll(&fd_watcher);
 
   gpr_mu_lock(&pollset->mu);
   pollset->counter = 0;