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authorRickard Green <[email protected]>2016-06-20 15:51:25 +0200
committerRickard Green <[email protected]>2016-06-22 17:13:45 +0200
commitb71dde8bd94985f5953a1647802ac312a798fe69 (patch)
treed9aa5f8970daaff01d2e925e6fea7727ad233a77 /erts/lib_src/pthread
parent3b7a6ffddc819bf305353a593904cea9e932e7dc (diff)
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Improve accuracy of timeouts using premature timeouts
Improve accuracy of timeouts using a premature timeout then return to sleep with a shorter timeout just before requested timeout. This approach is only used on certain platforms where we know it improves the accuracy of the timeouts, e.g. MacOS X.
Diffstat (limited to 'erts/lib_src/pthread')
-rw-r--r--erts/lib_src/pthread/ethr_event.c74
1 files changed, 56 insertions, 18 deletions
diff --git a/erts/lib_src/pthread/ethr_event.c b/erts/lib_src/pthread/ethr_event.c
index eef88d5002..464875570a 100644
--- a/erts/lib_src/pthread/ethr_event.c
+++ b/erts/lib_src/pthread/ethr_event.c
@@ -184,6 +184,8 @@ return_event_on:
#include <errno.h>
#include <string.h>
+#include "erl_misc_utils.h"
+
#ifdef __DARWIN__
struct ethr_event_fdsets___ {
@@ -346,12 +348,9 @@ wait__(ethr_event *e, int spincount, ethr_sint64_t timeout)
ethr_sint32_t val;
int res, ulres;
int until_yield = ETHR_YIELD_AFTER_BUSY_LOOPS;
- ethr_sint64_t time = 0; /* SHUT UP annoying faulty warning... */
+ ethr_sint64_t time = 0;
#ifdef ETHR_HAVE_ETHR_GET_MONOTONIC_TIME
- ethr_sint64_t start = 0; /* SHUT UP annoying faulty warning... */
-#endif
-#ifdef ETHR_HAVE_PTHREAD_COND_TIMEDWAIT_MONOTONIC
- struct timespec cond_timeout;
+ ethr_sint64_t timeout_time = 0; /* SHUT UP annoying faulty warning... */
#endif
val = ethr_atomic32_read(&e->state);
@@ -365,30 +364,27 @@ wait__(ethr_event *e, int spincount, ethr_sint64_t timeout)
if (timeout == 0)
return ETIMEDOUT;
else {
- time = timeout;
- switch (e->fd[0]) {
- case ETHR_EVENT_INVALID_FD__:
#ifdef ETHR_HAVE_ETHR_GET_MONOTONIC_TIME
- start = ethr_get_monotonic_time();
+ timeout_time = ethr_get_monotonic_time();
+ timeout_time += timeout;
#endif
+ switch (e->fd[0]) {
+ case ETHR_EVENT_INVALID_FD__:
+ time = timeout;
setup_nonblocking_pipe(e);
break;
#ifdef ETHR_HAVE_PTHREAD_COND_TIMEDWAIT_MONOTONIC
case ETHR_EVENT_COND_TIMEDWAIT__:
- time += ethr_get_monotonic_time();
- cond_timeout.tv_sec = time / (1000*1000*1000);
- cond_timeout.tv_nsec = time % (1000*1000*1000);
+ time = -1;
if (spincount == 0)
goto set_event_off_waiter;
break;
#endif
default:
+ time = timeout;
/* Already initialized pipe... */
if (spincount == 0)
goto set_select_timeout;
-#ifdef ETHR_HAVE_ETHR_GET_MONOTONIC_TIME
- start = ethr_get_monotonic_time();
-#endif
break;
}
}
@@ -418,6 +414,9 @@ wait__(ethr_event *e, int spincount, ethr_sint64_t timeout)
|| e->fd[0] == ETHR_EVENT_COND_TIMEDWAIT__
#endif
) {
+#ifdef ETHR_HAVE_PTHREAD_COND_TIMEDWAIT_MONOTONIC
+ struct timespec cond_timeout;
+#endif
set_event_off_waiter:
@@ -446,9 +445,35 @@ wait__(ethr_event *e, int spincount, ethr_sint64_t timeout)
#ifdef ETHR_HAVE_PTHREAD_COND_TIMEDWAIT_MONOTONIC
if (timeout > 0) {
+ if (time != timeout_time) {
+ time = timeout_time;
+
+#if ERTS_USE_PREMATURE_TIMEOUT
+ {
+ ethr_sint64_t rtmo;
+
+ rtmo = timeout_time - ethr_get_monotonic_time();
+ if (rtmo <= 0) {
+ res = ETIMEDOUT;
+ break;
+ }
+ time = timeout_time;
+ time -= ERTS_PREMATURE_TIMEOUT(rtmo, 1000*1000*1000);
+ }
+#endif
+
+ cond_timeout.tv_sec = time / (1000*1000*1000);
+ cond_timeout.tv_nsec = time % (1000*1000*1000);
+ }
res = pthread_cond_timedwait(&e->cnd, &e->mtx, &cond_timeout);
- if (res == EINTR || res == ETIMEDOUT)
+ if (res == EINTR
+ || (res == ETIMEDOUT
+#if ERTS_USE_PREMATURE_TIMEOUT
+ && time == timeout_time
+#endif
+ )) {
break;
+ }
}
else
#endif
@@ -477,7 +502,11 @@ wait__(ethr_event *e, int spincount, ethr_sint64_t timeout)
struct timeval select_timeout;
#ifdef ETHR_HAVE_ETHR_GET_MONOTONIC_TIME
- time -= ethr_get_monotonic_time() - start;
+#if ERTS_USE_PREMATURE_TIMEOUT
+ restart_select:
+#endif
+
+ time = timeout_time - ethr_get_monotonic_time();
if (time <= 0)
return ETIMEDOUT;
#endif
@@ -492,6 +521,11 @@ wait__(ethr_event *e, int spincount, ethr_sint64_t timeout)
*/
time = ((time - 1) / 1000) + 1;
+#if defined(ETHR_HAVE_ETHR_GET_MONOTONIC_TIME) \
+ && ERTS_USE_PREMATURE_TIMEOUT
+ time -= ERTS_PREMATURE_TIMEOUT(time, 1000*1000);
+#endif
+
select_timeout.tv_sec = time / (1000*1000);
select_timeout.tv_usec = time % (1000*1000);
@@ -559,7 +593,11 @@ wait__(ethr_event *e, int spincount, ethr_sint64_t timeout)
val = ethr_atomic32_read(&e->state);
if (val == ETHR_EVENT_ON__)
goto return_event_on;
-
+#if defined(ETHR_HAVE_ETHR_GET_MONOTONIC_TIME) \
+ && ERTS_USE_PREMATURE_TIMEOUT
+ if (res == ETIMEDOUT)
+ goto restart_select; /* Verify timeout */
+#endif
}
return res;