llc: Calculate the average queuing delay of the LLC queues
Use a formula like it is used with TCP. This can help to make
decisions about if frames should be dropped or not at the time
we enqueue them.
This code will store two timeval structs in fron the of the
actual data and compute the average at the time of the dequeue.
diff --git a/src/llc.cpp b/src/llc.cpp
index c557584..2d295f8 100644
--- a/src/llc.cpp
+++ b/src/llc.cpp
@@ -78,14 +78,34 @@
{
INIT_LLIST_HEAD(&queue);
m_queue_size = 0;
+ m_avg_queue_delay = 0;
reset();
}
+#define ALPHA 0.5f
+
struct msgb *gprs_llc::dequeue()
{
- if (m_queue_size > 0)
- m_queue_size -= 1;
- return msgb_dequeue(&queue);
+ struct msgb *msg;
+ struct timeval *tv, tv_now, tv_result;
+ uint32_t lifetime;
+
+
+ msg = msgb_dequeue(&queue);
+ if (!msg)
+ return NULL;
+
+ m_queue_size -= 1;
+
+ /* take the second time */
+ gettimeofday(&tv_now, NULL);
+ tv = (struct timeval *)&msg->data[sizeof(*tv)];
+ timersub(&tv_now, tv, &tv_result);
+
+ lifetime = tv_result.tv_sec*1000 + tv_result.tv_usec/1000;
+ m_avg_queue_delay = m_avg_queue_delay * ALPHA + lifetime * (1-ALPHA);
+
+ return msg;
}
diff --git a/src/llc.h b/src/llc.h
index f29c929..1f0c114 100644
--- a/src/llc.h
+++ b/src/llc.h
@@ -55,6 +55,7 @@
uint16_t m_length; /* len of current DL LLC_frame, 0 == no frame */
struct llist_head queue; /* queued LLC DL data */
+ uint32_t m_avg_queue_delay; /* Average delay of data going through the queue */
size_t m_queue_size;
};
diff --git a/src/tbf.cpp b/src/tbf.cpp
index 4c0e845..5d7e4ef 100644
--- a/src/tbf.cpp
+++ b/src/tbf.cpp
@@ -100,12 +100,14 @@
/* the TBF exists, so we must write it in the queue
* we prepend lifetime in front of PDU */
struct timeval *tv;
- struct msgb *llc_msg = msgb_alloc(len + sizeof(*tv),
+ struct msgb *llc_msg = msgb_alloc(len + sizeof(*tv) * 2,
"llc_pdu_queue");
if (!llc_msg)
return -ENOMEM;
tv = (struct timeval *)msgb_put(llc_msg, sizeof(*tv));
gprs_llc::calc_pdu_lifetime(bts, pdu_delay_csec, tv);
+ tv = (struct timeval *)msgb_put(llc_msg, sizeof(*tv));
+ gettimeofday(tv, NULL);
memcpy(msgb_put(llc_msg, len), data, len);
m_llc.enqueue(llc_msg);
tbf_update_ms_class(this, ms_class);
@@ -633,6 +635,7 @@
while ((msg = m_llc.dequeue())) {
tv = (struct timeval *)msg->data;
msgb_pull(msg, sizeof(*tv));
+ msgb_pull(msg, sizeof(*tv));
if (gprs_llc::is_frame_expired(&tv_now, tv)) {
LOGP(DRLCMACDL, LOGL_NOTICE, "%s Discarding LLC PDU "