DAOS-8781 client: allow polling timeout to be modified via env (#12124)

Introduce a new env variable called D_POLL_TIMEOUT in libdaos
to tune how aggressive the polling on network progress is for synchronous
operation. For asynchronous operations, the caller already passes
a timeout to eq_poll or event_test.
The default value (0) is not changed and means busy polling.
This can be modified to a value in micro-seconds.

Signed-off-by: Johann Lombardi <[email protected]>

Author: johannlombardi

docs/admin/env_variables.md

@@ -68,6 +68,7 @@ Environment variables in this section only apply to the client side.
 |Variable                 |Description|
 |-------------------------|-----------|
 |FI\_MR\_CACHE\_MAX\_COUNT|Enable MR (Memory Registration) caching in OFI layer. Recommended to be set to 0 (disable) when CRT\_DISABLE\_MEM\_PIN is NOT set to 1. INTEGER. Default to unset.|
+|D\_POLL\_TIMEOUT|Polling timeout passed to network progress for synchronous operations. Default to 0 (busy polling), value in micro-seconds otherwise.|
 
 
 ## Debug System (Client & Server)

src/cart/crt_init.c

@@ -71,7 +71,8 @@ dump_envariables(void)
 		"CRT_CTX_SHARE_ADDR", "CRT_CTX_NUM", "D_FI_CONFIG",
 		"FI_UNIVERSE_SIZE", "CRT_ENABLE_MEM_PIN",
 		"FI_OFI_RXM_USE_SRX", "D_LOG_FLUSH", "CRT_MRC_ENABLE",
-		"CRT_SECONDARY_PROVIDER", "D_PROVIDER_AUTH_KEY", "D_PORT_AUTO_ADJUST"};
+		"CRT_SECONDARY_PROVIDER", "D_PROVIDER_AUTH_KEY", "D_PORT_AUTO_ADJUST",
+		"D_POOL_TIMEOUT"};
 
 	D_INFO("-- ENVARS: --\n");
 	for (i = 0; i < ARRAY_SIZE(envars); i++) {

src/client/api/event.c

@@ -20,6 +20,12 @@
 static __thread daos_event_t	ev_thpriv;
 static __thread bool		ev_thpriv_is_init;
 
+/**
+ * Global progress timeout for synchronous operation
+ * busy-polling by default (0), timeout in us otherwise
+ */
+static uint32_t ev_prog_timeout;
+
 #define EQ_WITH_CRT
 
 #if !defined(EQ_WITH_CRT)
@@ -91,6 +97,8 @@ daos_eq_lib_init()
 
 	eq_ref = 1;
 
+	d_getenv_int("D_POLL_TIMEOUT", &ev_prog_timeout);
+
 unlock:
 	D_MUTEX_UNLOCK(&daos_eq_lock);
 	return rc;
@@ -1262,7 +1270,7 @@ daos_event_priv_wait()
 
 	/* Wait on the event to complete */
 	while (evx->evx_status != DAOS_EVS_READY) {
-		rc = crt_progress_cond(evx->evx_ctx, 0, ev_progress_cb, &epa);
+		rc = crt_progress_cond(evx->evx_ctx, ev_prog_timeout, ev_progress_cb, &epa);
 
 		/** progress succeeded, loop can exit if event completed */
 		if (rc == 0) {