[ovs-dev] [PATCH v5 2/2] Minimize the number of time calls in time_poll()
anton.ivanov at cambridgegreys.com
anton.ivanov at cambridgegreys.com
Wed Aug 4 08:34:19 UTC 2021
From: Anton Ivanov <anton.ivanov at cambridgegreys.com>
time_poll() makes an excessive number of time_msec() calls
which incur a performance penalty.
1. Avoid time_msec() call for timeout calculation when time_poll()
is asked to skip poll()
2. Reuse the time_msec() result from deadline calculation for
last_wakeup and timeout calculation.
Signed-off-by: Anton Ivanov <anton.ivanov at cambridgegreys.com>
---
lib/timeval.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/lib/timeval.c b/lib/timeval.c
index dbfbcb9e6..45a934513 100644
--- a/lib/timeval.c
+++ b/lib/timeval.c
@@ -287,7 +287,7 @@ time_poll(struct pollfd *pollfds, int n_pollfds, HANDLE *handles OVS_UNUSED,
long long int timeout_when, int *elapsed)
{
long long int *last_wakeup = last_wakeup_get();
- long long int start;
+ long long int start, now;
bool quiescent;
int retval = 0;
@@ -297,13 +297,12 @@ time_poll(struct pollfd *pollfds, int n_pollfds, HANDLE *handles OVS_UNUSED,
if (*last_wakeup && !thread_is_pmd()) {
log_poll_interval(*last_wakeup);
}
- start = time_msec();
+ now = start = time_msec();
timeout_when = MIN(timeout_when, deadline);
quiescent = ovsrcu_is_quiescent();
for (;;) {
- long long int now = time_msec();
int time_left;
retval = 0;
@@ -331,6 +330,8 @@ time_poll(struct pollfd *pollfds, int n_pollfds, HANDLE *handles OVS_UNUSED,
*/
if (timeout_when != LLONG_MIN) {
retval = poll(pollfds, n_pollfds, time_left);
+ } else {
+ retval = 0;
}
if (retval < 0) {
retval = -errno;
@@ -357,7 +358,8 @@ time_poll(struct pollfd *pollfds, int n_pollfds, HANDLE *handles OVS_UNUSED,
ovsrcu_quiesce_end();
}
- if (deadline <= time_msec()) {
+ now = time_msec();
+ if (deadline <= now) {
#ifndef _WIN32
fatal_signal_handler(SIGALRM);
#else
@@ -374,7 +376,7 @@ time_poll(struct pollfd *pollfds, int n_pollfds, HANDLE *handles OVS_UNUSED,
break;
}
}
- *last_wakeup = time_msec();
+ *last_wakeup = now;
refresh_rusage();
*elapsed = *last_wakeup - start;
return retval;
--
2.20.1
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