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osmo-pcu
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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.
This commit is contained in:
Daniel Willmann 2013-12-04 18:11:47 +01:00 committed by Holger Hans Peter Freyther
parent a42b2ad5ed
commit 9c623892f5
3 changed files with 28 additions and 4 deletions
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26
src/llc.cpp
View File

@ -78,14 +78,34 @@ void gprs_llc::init()
{
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;
}

1
src/llc.h
View File

@ -55,6 +55,7 @@ struct gprs_llc {
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;
};

5
src/tbf.cpp
View File

@ -100,12 +100,14 @@ int gprs_rlcmac_tbf::append_data(const uint8_t ms_class,
/* 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 @@ struct msgb *gprs_rlcmac_tbf::llc_dequeue(bssgp_bvc_ctx *bctx)
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 "