From e860fc4a48605a9c3f9cb12782ef92a6bc855e2b Mon Sep 17 00:00:00 2001
From: Marek Vavrusa <marek.vavrusa@nic.cz>
Date: Tue, 8 May 2012 18:31:57 +0200
Subject: [PATCH] Set affinity of the UDP threads to specific cores on Linux.
Partial core overlap was implemented to prevent stalls and
better utilization of free cores by the scheduler. Not portable.
---
configure.ac | 2 +-
src/knot/server/dthreads.c | 51 ++++++++++++++++++++++++++++++++---
src/knot/server/dthreads.h | 33 ++++++++++++++++++++++-
src/knot/server/udp-handler.c | 26 ++++++++++++++++++
4 files changed, 106 insertions(+), 6 deletions(-)
diff --git a/configure.ac b/configure.ac
index 2e481c5dd7..2e869a7fee 100644
--- a/configure.ac
+++ b/configure.ac
@@ -164,7 +164,7 @@ AC_DEFINE([DSFMT_MEXP], [521], [DSFMT parameters.])
# Checks for library functions.
AC_FUNC_FORK
AC_FUNC_MMAP
-AC_CHECK_FUNCS([gethostbyname gettimeofday clock_gettime memalign memmove memset munmap regcomp pselect select socket sqrt strcasecmp strchr strdup strerror strncasecmp strtol strtoul poll epoll_wait kqueue setgroups sendmmsg madvise])
+AC_CHECK_FUNCS([gethostbyname gettimeofday clock_gettime memalign memmove memset munmap regcomp pselect select socket sqrt strcasecmp strchr strdup strerror strncasecmp strtol strtoul poll epoll_wait kqueue setgroups sendmmsg madvise pthread_setaffinity_np])
AC_CONFIG_FILES([Makefile
samples/Makefile
diff --git a/src/knot/server/dthreads.c b/src/knot/server/dthreads.c
index 4e2b490fbc..fcf732293d 100644
--- a/src/knot/server/dthreads.c
+++ b/src/knot/server/dthreads.c
@@ -854,6 +854,25 @@ int dt_stop(dt_unit_t *unit)
// return KNOTD_EOK;
//}
+int dt_setaffinity(dthread_t *thread, cpu_set_t *mask)
+{
+ if (thread == NULL || mask == NULL) {
+ return KNOTD_EINVAL;
+ }
+
+#ifdef HAVE_PTHREAD_SETAFFINITY_NP
+ pthread_t tid = pthread_self();
+ int ret = pthread_setaffinity_np(tid, sizeof(cpu_set_t), mask);
+ if (ret < 0) {
+ return KNOTD_ERROR;
+ }
+#else
+ return KNOTD_ENOTSUP;
+#endif
+
+ return KNOTD_EOK;
+}
+
int dt_repurpose(dthread_t *thread, runnable_t runnable, void *data)
{
// Check
@@ -963,14 +982,22 @@ int dt_compact(dt_unit_t *unit)
return KNOTD_EOK;
}
-int dt_optimal_size()
+int dt_online_cpus()
{
+ int ret = -1;
#ifdef _SC_NPROCESSORS_ONLN
- int ret = (int) sysconf(_SC_NPROCESSORS_ONLN);
- if (ret >= 1) {
+ ret = (int) sysconf(_SC_NPROCESSORS_ONLN);
+#endif
+ return ret;
+}
+
+int dt_optimal_size()
+{
+ int ret = dt_online_cpus();
+ if (ret > 0) {
return ret + CPU_ESTIMATE_MAGIC;
}
-#endif
+
dbg_dt("dthreads: failed to fetch the number of online CPUs.");
return DEFAULT_THR_COUNT;
}
@@ -993,6 +1020,22 @@ int dt_is_cancelled(dthread_t *thread)
return ret;
}
+unsigned dt_get_id(dthread_t *thread)
+{
+ if (thread == NULL || thread->unit == NULL) {
+ return 0;
+ }
+
+ dt_unit_t *unit = thread->unit;
+ for(unsigned tid = 0; tid < unit->size; ++tid) {
+ if (thread == unit->threads[tid]) {
+ return tid;
+ }
+ }
+
+ return 0;
+}
+
int dt_unit_lock(dt_unit_t *unit)
{
// Check input
diff --git a/src/knot/server/dthreads.h b/src/knot/server/dthreads.h
index 2347e1da76..08ee80bc14 100644
--- a/src/knot/server/dthreads.h
+++ b/src/knot/server/dthreads.h
@@ -250,6 +250,17 @@ int dt_stop(dt_unit_t *unit);
*/
//int dt_setprio(dthread_t *thread, int prio);
+/*!
+ * \brief Set thread affinity to masked CPU's.
+ *
+ * \param thread Target thread instance.
+ * \param mask CPU mask.
+ *
+ * \retval KNOTD_EOK on success.
+ * \retval KNOTD_EINVAL on invalid parameters.
+ */
+int dt_setaffinity(dthread_t *thread, cpu_set_t *mask);
+
/*!
* \brief Set thread to execute another runnable.
*
@@ -306,10 +317,18 @@ int dt_cancel(dthread_t *thread);
*/
int dt_compact(dt_unit_t *unit);
+/*!
+ * \brief Return number of online processors.
+ *
+ * \retval Number of online CPU's if success.
+ * \retval <0 on failure.
+ */
+int dt_online_cpus();
+
/*!
* \brief Return optimal number of threads for instance.
*
- * It is estimated as NUM_CPUs + 1.
+ * It is estimated as NUM_CPUs + CONSTANT.
* Fallback is DEFAULT_THR_COUNT (\see common.h).
*
* \return Number of threads.
@@ -328,6 +347,18 @@ int dt_optimal_size();
*/
int dt_is_cancelled(dthread_t *thread);
+
+/*!
+ * \brief Return thread index in threading unit.
+ *
+ * \note Returns 0 when thread doesn't have a unit.
+ *
+ * \param thread Target thread instance.
+ *
+ * \return Thread index.
+ */
+unsigned dt_get_id(dthread_t *thread);
+
/*!
* \brief Lock unit to prevent parallel operations which could alter unit
* at the same time.
diff --git a/src/knot/server/udp-handler.c b/src/knot/server/udp-handler.c
index 6fbf6a2d3e..72671b0d92 100644
--- a/src/knot/server/udp-handler.c
+++ b/src/knot/server/udp-handler.c
@@ -201,6 +201,19 @@ static inline int udp_master_recvfrom(dthread_t *thread, stat_t *thread_stat)
return KNOTD_EINVAL;
}
+ /* Set CPU affinity to improve load distribution on multicore systems.
+ * Partial overlapping mask to be nice to scheduler.
+ */
+ int cpcount = dt_online_cpus();
+ if (cpcount > 0) {
+ unsigned tid = dt_get_id(thread);
+ cpu_set_t cpus;
+ CPU_ZERO(&cpus);
+ CPU_SET(tid % cpcount, &cpus);
+ CPU_SET((tid + 1) % cpcount, &cpus);
+ dt_setaffinity(thread, &cpus);
+ }
+
knot_nameserver_t *ns = h->server->nameserver;
/* Initialize remote party address. */
@@ -388,6 +401,19 @@ static inline int udp_master_recvmmsg(dthread_t *thread, stat_t *thread_stat)
msgs[i].msg_hdr.msg_name = addrs[i].ptr;
msgs[i].msg_hdr.msg_namelen = addrs[i].len;
}
+
+ /* Set CPU affinity to improve load distribution on multicore systems.
+ * Partial overlapping mask to be nice to scheduler.
+ */
+ int cpcount = dt_online_cpus();
+ if (cpcount > 0) {
+ unsigned tid = dt_get_id(thread);
+ cpu_set_t cpus;
+ CPU_ZERO(&cpus);
+ CPU_SET(tid % cpcount, &cpus);
+ CPU_SET((tid + 1) % cpcount, &cpus);
+ dt_setaffinity(thread, &cpus);
+ }
/* Loop until all data is read. */
ssize_t n = 0;
--
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