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Fix: eliminate false epoch drop reports on TX sessions #1478

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Fix: eliminate false epoch drop reports on TX sessions #1478

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403e47c
Fix: eliminate false epoch drop reports on TX sessions
Sakoram Apr 3, 2026
96de579
Test: add epoch drop tests for st20p, st30p, st40p TX sessions
Sakoram Apr 3, 2026
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49 changes: 16 additions & 33 deletions lib/src/st2110/st_tx_ancillary_session.c
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Original file line number Diff line number Diff line change
Expand Up @@ -278,14 +278,6 @@ static int tx_ancillary_session_init_pacing(struct st_tx_ancillary_session_impl*
return 0;
}

static int tx_ancillary_session_init_pacing_epoch(
struct mtl_main_impl* impl, struct st_tx_ancillary_session_impl* s) {
uint64_t ptp_time = mt_get_ptp_time(impl, MTL_PORT_P);
struct st_tx_ancillary_session_pacing* pacing = &s->pacing;
pacing->cur_epochs = ptp_time / pacing->frame_time;
return 0;
}

static inline uint64_t tx_ancillary_pacing_time(
struct st_tx_ancillary_session_pacing* pacing, uint64_t epochs) {
return nextafter(epochs * pacing->frame_time, INFINITY);
Expand Down Expand Up @@ -344,7 +336,13 @@ static inline uint64_t tx_ancillary_calc_epoch(struct st_tx_ancillary_session_im
uint64_t cur_tai, uint64_t required_tai) {
struct st_tx_ancillary_session_pacing* pacing = &s->pacing;
uint64_t current_epoch = cur_tai / pacing->frame_time;
uint64_t next_free_epoch = pacing->cur_epochs + 1;
/*
* cur_epochs is 0 before the first frame (zero-initialized struct).
* Real PTP-derived epochs are ~10^11, so 0 is a safe "uninitialized" sentinel.
* On first call, start from current_epoch to avoid a false epoch_drop.
*/
uint64_t next_free_epoch =
likely(pacing->cur_epochs) ? pacing->cur_epochs + 1 : current_epoch;
uint64_t epoch = next_free_epoch;

if (required_tai) {
Expand All @@ -365,14 +363,16 @@ static inline uint64_t tx_ancillary_calc_epoch(struct st_tx_ancillary_session_im
} else {
dbg("%s(%d), frame is late, current_epoch %" PRIu64 " next_free_epoch %" PRIu64 "\n",
__func__, s->idx, current_epoch, next_free_epoch);
ST_SESSION_STAT_ADD(s, port_user_stats.common, stat_epoch_drop,
(current_epoch - next_free_epoch));

if (s->ops.notify_frame_late) {
s->ops.notify_frame_late(s->ops.priv, current_epoch - next_free_epoch);
if (!required_tai) {
ST_SESSION_STAT_ADD(s, port_user_stats.common, stat_epoch_drop,
(current_epoch - next_free_epoch));
if (s->ops.notify_frame_late) {
s->ops.notify_frame_late(s->ops.priv, current_epoch - next_free_epoch);
}
epoch = current_epoch;
}

epoch = current_epoch;
/* when required_tai is set, keep user-derived epoch — scheduler jitter
* does not mean the user dropped epochs */
}

return epoch;
Expand Down Expand Up @@ -448,22 +448,6 @@ static int tx_ancillary_session_init(struct st_tx_ancillary_sessions_mgr* mgr,
return 0;
}

static int tx_ancillary_sessions_tasklet_start(void* priv) {
struct st_tx_ancillary_sessions_mgr* mgr = priv;
struct mtl_main_impl* impl = mgr->parent;
struct st_tx_ancillary_session_impl* s;

for (int sidx = 0; sidx < mgr->max_idx; sidx++) {
s = tx_ancillary_session_get(mgr, sidx);
if (!s) continue;

tx_ancillary_session_init_pacing_epoch(impl, s);
tx_ancillary_session_put(mgr, sidx);
}

return 0;
}

static int tx_ancillary_session_update_redundant(struct st_tx_ancillary_session_impl* s,
struct rte_mbuf* pkt_r) {
struct mt_udp_hdr* hdr = rte_pktmbuf_mtod(pkt_r, struct mt_udp_hdr*);
Expand Down Expand Up @@ -1918,7 +1902,6 @@ static int tx_ancillary_sessions_mgr_init(struct mtl_main_impl* impl,
memset(&ops, 0x0, sizeof(ops));
ops.priv = mgr;
ops.name = "tx_ancillary_sessions_mgr";
ops.start = tx_ancillary_sessions_tasklet_start;
ops.handler = tx_ancillary_sessions_tasklet_handler;

mgr->tasklet = mtl_sch_register_tasklet(sch, &ops);
Expand Down
41 changes: 13 additions & 28 deletions lib/src/st2110/st_tx_audio_session.c
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Original file line number Diff line number Diff line change
Expand Up @@ -219,14 +219,6 @@ static int tx_audio_session_init_pacing(struct st_tx_audio_session_impl* s) {
return 0;
}

static int tx_audio_session_init_pacing_epoch(struct mtl_main_impl* impl,
struct st_tx_audio_session_impl* s) {
uint64_t ptp_time = mt_get_ptp_time(impl, MTL_PORT_P);
struct st_tx_audio_session_pacing* pacing = &s->pacing;
pacing->cur_epochs = ptp_time / pacing->trs;
return 0;
}

static inline double tx_audio_pacing_time(struct st_tx_audio_session_pacing* pacing,
uint64_t epochs) {
return epochs * pacing->trs;
Expand Down Expand Up @@ -268,7 +260,7 @@ static int tx_audio_session_sync_pacing(struct mtl_main_impl* impl,
long double pkt_time = pacing->trs;
/* always use MTL_PORT_P for ptp now */
uint64_t ptp_time = mt_get_ptp_time(impl, MTL_PORT_P);
uint64_t next_epochs = pacing->cur_epochs + 1;
uint64_t next_epochs;
uint64_t epochs;
double to_epoch;
uint64_t ptp_epochs;
Expand All @@ -286,6 +278,13 @@ static int tx_audio_session_sync_pacing(struct mtl_main_impl* impl,
epochs = ptp_time / pkt_time;
}

/*
* cur_epochs is 0 before the first frame (zero-initialized struct).
* Real PTP-derived epochs are ~10^11, so 0 is a safe "uninitialized" sentinel.
* On first call, start from ptp-derived epoch to avoid a false epoch_drop.
*/
next_epochs = likely(pacing->cur_epochs) ? pacing->cur_epochs + 1 : epochs;

dbg("%s(%d), epochs %" PRIu64 " %" PRIu64 "\n", __func__, s->idx, epochs,
pacing->cur_epochs);
if (epochs <= pacing->cur_epochs) {
Expand Down Expand Up @@ -325,8 +324,11 @@ static int tx_audio_session_sync_pacing(struct mtl_main_impl* impl,
}

if (epochs > next_epochs) {
ST_SESSION_STAT_ADD(s, port_user_stats.common, stat_epoch_drop,
(epochs - next_epochs));
/* skip drop accounting when user controls pacing — epoch jumps are intentional */
if (!required_tai) {
ST_SESSION_STAT_ADD(s, port_user_stats.common, stat_epoch_drop,
(epochs - next_epochs));
}
}

if (epochs < next_epochs) {
Expand Down Expand Up @@ -395,22 +397,6 @@ static int tx_audio_session_init(struct st_tx_audio_sessions_mgr* mgr,
return 0;
}

static int tx_audio_sessions_tasklet_start(void* priv) {
struct st_tx_audio_sessions_mgr* mgr = priv;
struct mtl_main_impl* impl = mgr->parent;
struct st_tx_audio_session_impl* s;

for (int sidx = 0; sidx < mgr->max_idx; sidx++) {
s = tx_audio_session_get(mgr, sidx);
if (!s) continue;

tx_audio_session_init_pacing_epoch(impl, s);
tx_audio_session_put(mgr, sidx);
}

return 0;
}

static int tx_audio_session_update_redundant(struct st_tx_audio_session_impl* s,
struct rte_mbuf* pkt_r) {
struct mt_udp_hdr* hdr = rte_pktmbuf_mtod(pkt_r, struct mt_udp_hdr*);
Expand Down Expand Up @@ -2433,7 +2419,6 @@ static int tx_audio_sessions_mgr_init(struct mtl_main_impl* impl,
memset(&ops, 0x0, sizeof(ops));
ops.priv = mgr;
ops.name = "tx_audio_sessions";
ops.start = tx_audio_sessions_tasklet_start;
ops.handler = tx_audio_sessions_tasklet;

mgr->tasklet = mtl_sch_register_tasklet(sch, &ops);
Expand Down
37 changes: 10 additions & 27 deletions lib/src/st2110/st_tx_fastmetadata_session.c
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Original file line number Diff line number Diff line change
Expand Up @@ -215,14 +215,6 @@ static int tx_fastmetadata_session_init_pacing(
return 0;
}

static int tx_fastmetadata_session_init_pacing_epoch(
struct mtl_main_impl* impl, struct st_tx_fastmetadata_session_impl* s) {
uint64_t ptp_time = mt_get_ptp_time(impl, MTL_PORT_P);
struct st_tx_fastmetadata_session_pacing* pacing = &s->pacing;
pacing->cur_epochs = ptp_time / pacing->frame_time;
return 0;
}

static inline double tx_fastmetadata_pacing_time(
struct st_tx_fastmetadata_session_pacing* pacing, uint64_t epochs) {
return epochs * pacing->frame_time;
Expand Down Expand Up @@ -264,7 +256,7 @@ static int tx_fastmetadata_session_sync_pacing(struct mtl_main_impl* impl,
double frame_time = pacing->frame_time;
/* always use MTL_PORT_P for ptp now */
uint64_t ptp_time = mt_get_ptp_time(impl, MTL_PORT_P);
uint64_t next_epochs = pacing->cur_epochs + 1;
uint64_t next_epochs;
uint64_t epochs;
double to_epoch;
bool interlaced = s->ops.interlaced;
Expand All @@ -281,6 +273,13 @@ static int tx_fastmetadata_session_sync_pacing(struct mtl_main_impl* impl,
epochs = ptp_time / frame_time;
}

/*
* cur_epochs is 0 before the first frame (zero-initialized struct).
* Real PTP-derived epochs are ~10^11, so 0 is a safe "uninitialized" sentinel.
* On first call, start from ptp-derived epoch to avoid a false epoch_drop.
*/
next_epochs = likely(pacing->cur_epochs) ? pacing->cur_epochs + 1 : epochs;

dbg("%s(%d), epochs %" PRIu64 " %" PRIu64 "\n", __func__, s->idx, epochs,
pacing->cur_epochs);
if (epochs <= pacing->cur_epochs) {
Expand All @@ -306,7 +305,8 @@ static int tx_fastmetadata_session_sync_pacing(struct mtl_main_impl* impl,
to_epoch = 0; /* send asap */
}

if (epochs > next_epochs) s->stat_epoch_drop += (epochs - next_epochs);
/* skip drop accounting when user controls pacing — epoch jumps are intentional */
if (epochs > next_epochs && !required_tai) s->stat_epoch_drop += (epochs - next_epochs);
if (epochs < next_epochs) {
ST_SESSION_STAT_ADD(s, port_user_stats.common, stat_epoch_onward,
(next_epochs - epochs));
Expand Down Expand Up @@ -355,22 +355,6 @@ static int tx_fastmetadata_session_init(struct st_tx_fastmetadata_sessions_mgr*
return 0;
}

static int tx_fastmetadata_sessions_tasklet_start(void* priv) {
struct st_tx_fastmetadata_sessions_mgr* mgr = priv;
struct mtl_main_impl* impl = mgr->parent;
struct st_tx_fastmetadata_session_impl* s;

for (int sidx = 0; sidx < mgr->max_idx; sidx++) {
s = tx_fastmetadata_session_get(mgr, sidx);
if (!s) continue;

tx_fastmetadata_session_init_pacing_epoch(impl, s);
tx_fastmetadata_session_put(mgr, sidx);
}

return 0;
}

static int tx_fastmetadata_session_update_redundant(
struct st_tx_fastmetadata_session_impl* s, struct rte_mbuf* pkt_r) {
struct mt_udp_hdr* hdr = rte_pktmbuf_mtod(pkt_r, struct mt_udp_hdr*);
Expand Down Expand Up @@ -1678,7 +1662,6 @@ static int tx_fastmetadata_sessions_mgr_init(
memset(&ops, 0x0, sizeof(ops));
ops.priv = mgr;
ops.name = "tx_fastmetadata_sessions_mgr";
ops.start = tx_fastmetadata_sessions_tasklet_start;
ops.handler = tx_fastmetadata_sessions_tasklet_handler;

mgr->tasklet = mtl_sch_register_tasklet(sch, &ops);
Expand Down
35 changes: 16 additions & 19 deletions lib/src/st2110/st_tx_video_session.c
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Original file line number Diff line number Diff line change
Expand Up @@ -604,14 +604,6 @@ static int tv_init_pacing(struct mtl_main_impl* impl,
return 0;
}

static int tv_init_pacing_epoch(struct mtl_main_impl* impl,
struct st_tx_video_session_impl* s) {
uint64_t ptp_time = mt_get_ptp_time(impl, MTL_PORT_P);
struct st_tx_video_pacing* pacing = &s->pacing;
pacing->cur_epochs = ptp_time / pacing->frame_time;
return 0;
}

static void validate_user_timestamp(struct st_tx_video_session_impl* s,
uint64_t requested_frame_count,
uint64_t current_frame_count) {
Expand All @@ -633,7 +625,13 @@ static inline uint64_t calc_frame_count_since_epoch(struct st_tx_video_session_i
uint64_t cur_tai,
uint64_t required_tai) {
uint64_t frame_count_tai = cur_tai / s->pacing.frame_time;
uint64_t next_free_frame_slot = s->pacing.cur_epochs + 1;
/*
* cur_epochs is 0 before the first frame (zero-initialized struct).
* Real PTP-derived epochs are ~10^11, so 0 is a safe "uninitialized" sentinel.
* On first call, start from frame_count_tai to avoid a false epoch_drop.
*/
uint64_t next_free_frame_slot =
likely(s->pacing.cur_epochs) ? s->pacing.cur_epochs + 1 : frame_count_tai;
uint64_t frame_count;

if (required_tai) {
Expand Down Expand Up @@ -661,14 +659,16 @@ static inline uint64_t calc_frame_count_since_epoch(struct st_tx_video_session_i
dbg("%s(%d), frame is late, frame_count_tai %" PRIu64 " next_free_frame_slot %" PRIu64
"\n",
__func__, s->idx, frame_count_tai, next_free_frame_slot);
ST_SESSION_STAT_ADD(s, port_user_stats.common, stat_epoch_drop,
(frame_count_tai - next_free_frame_slot));

if (s->ops.notify_frame_late) {
s->ops.notify_frame_late(s->ops.priv, frame_count_tai - next_free_frame_slot);
if (!required_tai) {
ST_SESSION_STAT_ADD(s, port_user_stats.common, stat_epoch_drop,
(frame_count_tai - next_free_frame_slot));
if (s->ops.notify_frame_late) {
s->ops.notify_frame_late(s->ops.priv, frame_count_tai - next_free_frame_slot);
}
frame_count = frame_count_tai;
}

frame_count = frame_count_tai;
/* when required_tai is set, keep user-derived frame_count — scheduler jitter
* does not mean the user dropped epochs */
}

return frame_count;
Expand Down Expand Up @@ -1746,8 +1746,6 @@ static int tv_tasklet_start(void* priv) {
for (int i = 0; i < s->ops.num_port; i++) {
s->last_burst_succ_time_tsc[i] = mt_get_tsc(impl);
}
/* calculate the pacing epoch */
tv_init_pacing_epoch(impl, s);
tx_video_session_put(mgr, sidx);
}

Expand Down Expand Up @@ -3359,7 +3357,6 @@ static int tv_attach(struct mtl_main_impl* impl, struct st_tx_video_sessions_mgr
s->last_burst_succ_time_tsc[i] = mt_get_tsc(impl);
}

tv_init_pacing_epoch(impl, s);
s->active = true;

info("%s(%d), len %d(%d) total %d each line %d type %d flags 0x%x, %s\n", __func__, idx,
Expand Down
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