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Encoder Pace setter / Traffic Shaper based on remaining free WiFi Tx_buffer free slots #450

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Encoder Pace setter / Traffic Shaper based on remaining free WiFi Tx_buffer free slots #450

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46 changes: 44 additions & 2 deletions src/tx.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -674,6 +674,24 @@ uint32_t extract_rxq_overflow(struct msghdr *msg)

void data_source(unique_ptr<Transmitter> &t, vector<int> &rx_fd, int control_fd, int fec_timeout, bool mirror, int log_interval)
{
int FEC_K = 0, FEC_N = 0;
int max_tx_buffer_size=64;
int treshold = 32;
// --- SHARED MEMORY INIT to read TxBuffer free slots---
volatile int *shared_wifi_free_cnt = nullptr;
int stats_fd = open("/dev/wifi_tx_buffer_free_frames", O_RDONLY);
if (stats_fd >= 0) {
void* mmap_ptr = mmap(NULL, 4096, PROT_READ, MAP_SHARED, stats_fd, 0);
if (mmap_ptr != MAP_FAILED) {
shared_wifi_free_cnt = (volatile int *)mmap_ptr;
WFB_INFO("TxBuffer Counter found!\r\n");
t->get_fec(FEC_K, FEC_N);
}
close(stats_fd); // The mapping persists after closing FD
}else
WFB_INFO(" NO TxBuffer Counter /dev/wifi_tx_buffer_free_frames\r\n");
// --- END SHARED MEMORY INIT ---

int nfds = rx_fd.size();
assert(nfds > 0);

Expand All @@ -700,6 +718,7 @@ void data_source(unique_ptr<Transmitter> &t, vector<int> &rx_fd, int control_fd,
uint32_t count_b_injected = 0; // successfully injected bytes (include additional fec packets)
uint32_t count_p_dropped = 0; // dropped due to rxq overflows or injection timeout
uint32_t count_p_truncated = 0; // injected large packets that were truncated
uint32_t count_p_wait_tx_buffer = 0;
int start_fd_idx = 0;

for(;;)
Expand All @@ -726,8 +745,8 @@ void data_source(unique_ptr<Transmitter> &t, vector<int> &rx_fd, int control_fd,
{
t->dump_stats(cur_ts, count_p_injected, count_p_dropped, count_b_injected);

IPC_MSG("%" PRIu64 "\tPKT\t%u:%u:%u:%u:%u:%u:%u\n",
cur_ts, count_p_fec_timeouts, count_p_incoming, count_b_incoming, count_p_injected, count_b_injected, count_p_dropped, count_p_truncated);
IPC_MSG("%" PRIu64 "\tPKT\t%u:%u:%u:%u:%u:%u:%u:%u\n",
cur_ts, count_p_fec_timeouts, count_p_incoming, count_b_incoming, count_p_injected, count_b_injected, count_p_dropped, count_p_truncated, count_p_wait_tx_buffer);
IPC_MSG_SEND();

if(count_p_dropped)
Expand All @@ -747,6 +766,7 @@ void data_source(unique_ptr<Transmitter> &t, vector<int> &rx_fd, int control_fd,
count_b_injected = 0;
count_p_dropped = 0;
count_p_truncated = 0;
count_p_wait_tx_buffer=0;

log_send_ts = cur_ts + log_interval - ((cur_ts - log_send_ts) % log_interval);
}
Expand Down Expand Up @@ -1002,6 +1022,23 @@ void data_source(unique_ptr<Transmitter> &t, vector<int> &rx_fd, int control_fd,
session_key_announce_ts = cur_ts + SESSION_KEY_ANNOUNCE_MSEC;
}


//Check TxBuffer only if exposed by the driver
if (stats_fd>0 && t->fragment_idx == 0 && shared_wifi_free_cnt != nullptr) {
//This can tune how aggressively we will control the encoder to slow down.
//Higher possible treshold wil force it slow down and drop frames more often.
//Lower treshold will increase jitter&delay, but with less dropped frames
treshold=max_tx_buffer_size - 1 * FEC_N; //Force CBR aggressively
//treshold= FEC_N;//max efficiency but more jitter

max_tx_buffer_size = std::max(max_tx_buffer_size, (int)*shared_wifi_free_cnt);//adjust max_tx_buffer_size if bigger
while (*shared_wifi_free_cnt <= treshold) {//buffer is usually 64, so 32 is a good compromise
// Driver is congested. Sleep for roughly 5-10ms. // This is long enough for the Linux scheduler to actually work and for the WiFi card to clear a chunk of its buffer.
usleep(5000);
count_p_wait_tx_buffer++;
}
}

t->send_packet(buf, rsize, 0);

if (cur_ts >= log_send_ts) // log timeout expired
Expand All @@ -1022,6 +1059,11 @@ void data_source(unique_ptr<Transmitter> &t, vector<int> &rx_fd, int control_fd,
fec_close_ts = get_time_ms() + fec_timeout;
}
}
// Clean up shared memory link
if (shared_wifi_free_cnt != nullptr) {
munmap((void*)shared_wifi_free_cnt, 4096);
shared_wifi_free_cnt = nullptr;
}
}


Expand Down
4 changes: 2 additions & 2 deletions src/tx.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,7 @@ class Transmitter
virtual void dump_stats(uint64_t ts, uint32_t &injected_packets, uint32_t &dropped_packets, uint32_t &injected_bytes) = 0;
virtual void update_radiotap_header(radiotap_header_t &radiotap_header) = 0;
virtual radiotap_header_t get_radiotap_header(void) = 0;
uint8_t fragment_idx;
protected:
virtual void inject_packet(const uint8_t *buf, size_t size) = 0;
virtual void set_mark(uint32_t idx) = 0;
Expand All @@ -95,8 +96,7 @@ class Transmitter
fec_t* fec_p;
int fec_k; // RS number of primary fragments in block
int fec_n; // RS total number of fragments in block
uint64_t block_idx; // (block_idx << 8) + fragment_idx = nonce (64bit)
uint8_t fragment_idx;
uint64_t block_idx; // (block_idx << 8) + fragment_idx = nonce (64bit)
uint8_t** block;
size_t max_packet_size;
const uint64_t epoch; // Packets from old epoch will be discarded
Expand Down
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