diff --git a/src/core/lib/iomgr/ev_epoll_linux.c b/src/core/lib/iomgr/ev_epoll_linux.c
index 3e13e657d35154b3d5c333c04bda0ad9edaebd2d..3a5f48cb8f0e8c94051f414a791f440fc4e378c4 100644
--- a/src/core/lib/iomgr/ev_epoll_linux.c
+++ b/src/core/lib/iomgr/ev_epoll_linux.c
@@ -40,6 +40,7 @@
#include <assert.h>
#include <errno.h>
+#include <limits.h>
#include <poll.h>
#include <pthread.h>
#include <signal.h>
@@ -62,6 +63,7 @@
#include "src/core/lib/iomgr/workqueue.h"
#include "src/core/lib/profiling/timers.h"
#include "src/core/lib/support/block_annotate.h"
+#include "src/core/lib/support/env.h"
/* TODO: sreek - Move this to init.c and initialize this like other tracers. */
static int grpc_polling_trace = 0; /* Disabled by default */
@@ -73,6 +75,10 @@ static int grpc_polling_trace = 0; /* Disabled by default */
/* Uncomment the following to enable extra checks on poll_object operations */
/* #define PO_DEBUG */
+/* The maximum number of polling threads per polling island. By default no
+ limit */
+static int g_max_pollers_per_pi = INT_MAX;
+
static int grpc_wakeup_signal = -1;
static bool is_grpc_wakeup_signal_initialized = false;
@@ -97,9 +103,6 @@ void grpc_use_signal(int signum) {
}
}
-/* The maximum number of polling threads per polling island */
-#define GRPC_MAX_POLLERS_PER_ISLAND 1
-
struct polling_island;
typedef enum {
@@ -1466,7 +1469,7 @@ static bool maybe_do_workqueue_work(grpc_exec_ctx *exec_ctx,
return false;
}
-/* NOTE: May modify 'now' */
+/* NOTE: This function may modify 'now' */
static bool acquire_polling_lease(grpc_pollset_worker *worker,
polling_island *pi, gpr_timespec deadline,
gpr_timespec *now) {
@@ -1475,7 +1478,7 @@ static bool acquire_polling_lease(grpc_pollset_worker *worker,
gpr_mu_lock(&pi->worker_list_mu); // LOCK
long num_pollers = gpr_atm_no_barrier_load(&pi->poller_count);
- if (num_pollers >= GRPC_MAX_POLLERS_PER_ISLAND) {
+ if (num_pollers >= g_max_pollers_per_pi) {
push_back_worker_node(&pi->worker_list_head, &worker->pi_list_link);
gpr_mu_unlock(&pi->worker_list_mu); // UNLOCK
@@ -1493,20 +1496,21 @@ static bool acquire_polling_lease(grpc_pollset_worker *worker,
if (errno == EAGAIN) {
is_timeout = true;
} else {
- /* TODO: sreek This should not happen. If we see these log messages, it
- * means we are most likely something incorrect in the setup needed for
- * sigwaitinfo/sigtimedwait */
- gpr_log(GPR_ERROR, "Failed with retcode: %d (timeout_ms: %d)", errno,
+ /* NOTE: This should not happen. If we see these log messages, it means
+ we are most likely doing something incorrect in the setup * needed
+ for sigwaitinfo/sigtimedwait */
+ gpr_log(GPR_ERROR,
+ "sigtimedwait failed with retcode: %d (timeout_ms: %d)", errno,
timeout_ms);
}
}
/* Did the worker come out of sigtimedwait due to a thread that just
- * exited epoll and kicking it (in release_polling_lease function). */
+ exited epoll and kicking it (in release_polling_lease function). */
bool is_polling_turn = gpr_atm_acq_load(&worker->is_polling_turn);
/* Did the worker come out of sigtimedwait due to a thread alerting it that
- * some completion event was (likely) available in the completion queue */
+ some completion event was (likely) available in the completion queue */
bool is_kicked = gpr_atm_no_barrier_load(&worker->is_kicked);
if (is_kicked || is_timeout) {
@@ -1522,11 +1526,11 @@ static bool acquire_polling_lease(grpc_pollset_worker *worker,
remove_worker_node(&worker->pi_list_link);
/* It is important to read the num_pollers again under the lock so that we
* have the latest num_pollers value that doesn't change while we are doing
- * the "(num_pollers < GPRC_MAX_POLLERS_PER_ISLAND)" a a few lines below */
+ * the "(num_pollers < g_max_pollers_per_pi)" a a few lines below */
num_pollers = gpr_atm_no_barrier_load(&pi->poller_count);
}
- if (num_pollers < GRPC_MAX_POLLERS_PER_ISLAND) {
+ if (num_pollers < g_max_pollers_per_pi) {
gpr_atm_no_barrier_fetch_add(&pi->poller_count, 1);
is_lease_acquired = true;
}
@@ -1536,7 +1540,7 @@ static bool acquire_polling_lease(grpc_pollset_worker *worker,
}
static void release_polling_lease(polling_island *pi, grpc_error **error) {
- gpr_mu_lock(&pi->worker_list_mu); // Lock
+ gpr_mu_lock(&pi->worker_list_mu);
gpr_atm_no_barrier_fetch_add(&pi->poller_count, -1);
worker_node *node = pop_front_worker_node(&pi->worker_list_head);
@@ -1554,6 +1558,8 @@ static void pollset_do_epoll_pwait(grpc_exec_ctx *exec_ctx, int epoll_fd,
grpc_pollset_worker *worker,
gpr_timespec now, gpr_timespec deadline,
sigset_t *sig_mask, grpc_error **error) {
+ /* Only g_max_pollers_per_pi threads can be doing polling in parallel.
+ If we cannot get a lease, we cannot continue to do epoll_pwait() */
if (!acquire_polling_lease(worker, pi, deadline, &now)) {
return;
}
@@ -1563,6 +1569,7 @@ static void pollset_do_epoll_pwait(grpc_exec_ctx *exec_ctx, int epoll_fd,
char *err_msg;
const char *err_desc = "pollset_work_and_unlock";
+ /* timeout_ms is the time between 'now' and 'deadline' */
int timeout_ms = poll_deadline_to_millis_timeout(deadline, now);
GRPC_SCHEDULING_START_BLOCKING_REGION;
@@ -1570,6 +1577,7 @@ static void pollset_do_epoll_pwait(grpc_exec_ctx *exec_ctx, int epoll_fd,
epoll_pwait(epoll_fd, ep_ev, GRPC_EPOLL_MAX_EVENTS, timeout_ms, sig_mask);
GRPC_SCHEDULING_END_BLOCKING_REGION;
+ /* Give back the lease right away so that some other thread can enter */
release_polling_lease(pi, error);
if (ep_rv < 0) {
@@ -2116,6 +2124,21 @@ static bool is_epoll_available() {
return true;
}
+/* This is mainly for testing purposes. Checks to see if environment variable
+ * GRPC_MAX_POLLERS_PER_PI is set and if so, assigns that value to the */
+static void set_max_pollers_per_island() {
+ char *s = gpr_getenv("GRPC_MAX_POLLERS_PER_PI");
+ if (s) {
+ int max_pollers = (int)strtol(s, NULL, 10);
+ if (max_pollers > 0) {
+ g_max_pollers_per_pi = max_pollers;
+ }
+ }
+
+ gpr_log(GPR_INFO, "Max number of pollers per polling island: %d",
+ g_max_pollers_per_pi);
+}
+
const grpc_event_engine_vtable *grpc_init_epoll_linux(void) {
/* If use of signals is disabled, we cannot use epoll engine*/
if (is_grpc_wakeup_signal_initialized && grpc_wakeup_signal < 0) {
@@ -2134,6 +2157,8 @@ const grpc_event_engine_vtable *grpc_init_epoll_linux(void) {
grpc_use_signal(SIGRTMIN + 6);
}
+ set_max_pollers_per_island();
+
fd_global_init();
if (!GRPC_LOG_IF_ERROR("pollset_global_init", pollset_global_init())) {