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diff --git a/sys/kern/subr_gtaskqueue.c b/sys/kern/subr_gtaskqueue.c
--- a/sys/kern/subr_gtaskqueue.c
+++ b/sys/kern/subr_gtaskqueue.c
@@ -342,14 +342,14 @@
struct epoch_tracker et;
struct gtaskqueue_busy tb;
struct gtask *gtask;
- bool in_net_epoch;
+ unsigned int epochtasks;
KASSERT(queue != NULL, ("tq is NULL"));
TQ_ASSERT_LOCKED(queue);
tb.tb_running = NULL;
LIST_INSERT_HEAD(&queue->tq_active, &tb, tb_link);
- in_net_epoch = false;
+ epochtasks = 0;
while ((gtask = STAILQ_FIRST(&queue->tq_queue)) != NULL) {
STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
gtask->ta_flags &= ~TASK_ENQUEUED;
@@ -358,19 +358,23 @@
TQ_UNLOCK(queue);
KASSERT(gtask->ta_func != NULL, ("task->ta_func is NULL"));
- if (!in_net_epoch && TASK_IS_NET(gtask)) {
- in_net_epoch = true;
- NET_EPOCH_ENTER(et);
- } else if (in_net_epoch && !TASK_IS_NET(gtask)) {
+ if (TASK_IS_NET(gtask)) {
+ if (epochtasks++ == 0)
+ NET_EPOCH_ENTER(et);
+ } else if (epochtasks > 0) {
NET_EPOCH_EXIT(et);
- in_net_epoch = false;
+ epochtasks = 0;
}
gtask->ta_func(gtask->ta_context);
+ if (epochtasks > net_epoch_task_limit) {
+ NET_EPOCH_EXIT(et);
+ epochtasks = 0;
+ }
TQ_LOCK(queue);
wakeup(gtask);
}
- if (in_net_epoch)
+ if (epochtasks > 0)
NET_EPOCH_EXIT(et);
LIST_REMOVE(&tb, tb_link);
}
diff --git a/sys/kern/subr_taskqueue.c b/sys/kern/subr_taskqueue.c
--- a/sys/kern/subr_taskqueue.c
+++ b/sys/kern/subr_taskqueue.c
@@ -43,6 +43,7 @@
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/stdarg.h>
+#include <sys/sysctl.h>
#include <sys/taskqueue.h>
#include <sys/unistd.h>
@@ -78,6 +79,19 @@
void *tq_cb_contexts[TASKQUEUE_NUM_CALLBACKS];
};
+static SYSCTL_NODE(_kern, OID_AUTO, taskqueue, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
+ "taskqueue information");
+
+/*
+ * Limit on the number of tasks that may be run in a single epoch section.
+ * It's profitable to batch tasks together, but there must be a bound in order
+ * to maintain system liveness.
+ */
+unsigned int net_epoch_task_limit = 8;
+SYSCTL_UINT(_kern_taskqueue, OID_AUTO, net_epoch_task_limit, CTLFLAG_RWTUN,
+ &net_epoch_task_limit, 0,
+ "Maximum number of tasks to run in an epoch section");
+
#define TQ_FLAGS_ACTIVE (1 << 0)
#define TQ_FLAGS_BLOCKED (1 << 1)
#define TQ_FLAGS_UNLOCKED_ENQUEUE (1 << 2)
@@ -486,15 +500,15 @@
struct epoch_tracker et;
struct taskqueue_busy tb;
struct task *task;
- bool in_net_epoch;
+ unsigned int epochtasks;
int pending;
KASSERT(queue != NULL, ("tq is NULL"));
TQ_ASSERT_LOCKED(queue);
tb.tb_running = NULL;
LIST_INSERT_HEAD(&queue->tq_active, &tb, tb_link);
- in_net_epoch = false;
+ epochtasks = 0;
while ((task = STAILQ_FIRST(&queue->tq_queue)) != NULL) {
STAILQ_REMOVE_HEAD(&queue->tq_queue, ta_link);
if (queue->tq_hint == task)
@@ -507,19 +521,23 @@
TQ_UNLOCK(queue);
KASSERT(task->ta_func != NULL, ("task->ta_func is NULL"));
- if (!in_net_epoch && TASK_IS_NET(task)) {
- in_net_epoch = true;
- NET_EPOCH_ENTER(et);
- } else if (in_net_epoch && !TASK_IS_NET(task)) {
+ if (TASK_IS_NET(task)) {
+ if (epochtasks++ == 0)
+ NET_EPOCH_ENTER(et);
+ } else if (epochtasks > 0) {
NET_EPOCH_EXIT(et);
- in_net_epoch = false;
+ epochtasks = 0;
}
task->ta_func(task->ta_context, pending);
+ if (epochtasks > net_epoch_task_limit) {
+ NET_EPOCH_EXIT(et);
+ epochtasks = 0;
+ }
TQ_LOCK(queue);
wakeup(task);
}
- if (in_net_epoch)
+ if (epochtasks > 0)
NET_EPOCH_EXIT(et);
LIST_REMOVE(&tb, tb_link);
}
diff --git a/sys/sys/taskqueue.h b/sys/sys/taskqueue.h
--- a/sys/sys/taskqueue.h
+++ b/sys/sys/taskqueue.h
@@ -221,4 +221,6 @@
*/
TASKQUEUE_DECLARE(bus);
+extern unsigned int net_epoch_task_limit;
+
#endif /* !_SYS_TASKQUEUE_H_ */

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