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rtl_sdr_fm: add batch operations and thread scheduling

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This commit is contained in:
arancormonk
2025-09-03 15:58:33 -04:00
parent 7dd9cd7566
commit 0decc5934c
1 changed files with 69 additions and 0 deletions
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69
src/rtl_sdr_fm.cpp
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@@ -26,6 +26,7 @@
#include <string.h>
#include <pthread.h>
#include <unistd.h>
#include <sched.h>
#include <atomic>
#include <rtl-sdr.h>
#include "dsd.h"
@@ -170,6 +171,64 @@ struct controller_state controller;
#define safe_cond_signal(n, m) pthread_mutex_lock(m); pthread_cond_signal(n); pthread_mutex_unlock(m)
#define safe_cond_wait(n, m) pthread_mutex_lock(m); pthread_cond_wait(n, m); pthread_mutex_unlock(m)
/* =====================
Thread Scheduling Helpers (optional realtime/affinity)
===================== */
static void maybe_set_thread_realtime_and_affinity(const char *role)
{
const char *enable = getenv("DSD_FME_RT_SCHED");
if (!enable || enable[0] != '1') {
return;
}
/* Optional: role-specific priority (1..99) for SCHED_FIFO */
int policy = SCHED_FIFO;
struct sched_param sp;
int pmax = sched_get_priority_max(policy);
int pmin = sched_get_priority_min(policy);
int def = (pmax > 10) ? (pmax - 10) : pmax; /* default near top, but safe */
char envname[64];
sp.sched_priority = def;
if (role) {
/* e.g., DSD_FME_RT_PRIO_DEMOD, DSD_FME_RT_PRIO_DONGLE */
snprintf(envname, sizeof(envname), "DSD_FME_RT_PRIO_%s", role);
const char *prio_str = getenv(envname);
if (prio_str && prio_str[0] != '\0') {
int pr = atoi(prio_str);
if (pr < pmin) pr = pmin;
if (pr > pmax) pr = pmax;
sp.sched_priority = pr;
}
}
if (pthread_setschedparam(pthread_self(), policy, &sp) != 0) {
fprintf(stderr, "WARNING: Failed to set %s thread to SCHED_FIFO (needs CAP_SYS_NICE).\n", role ? role : "RT");
} else {
fprintf(stderr, "%s thread SCHED_FIFO priority set to %d.\n", role ? role : "RT", sp.sched_priority);
}
/* Optional: role-specific CPU affinity: DSD_FME_CPU_DEMOD / DSD_FME_CPU_DONGLE */
if (role) {
snprintf(envname, sizeof(envname), "DSD_FME_CPU_%s", role);
const char *cpu_str = getenv(envname);
if (cpu_str && cpu_str[0] != '\0') {
int cpu = atoi(cpu_str);
if (cpu >= 0) {
cpu_set_t cpuset;
CPU_ZERO(&cpuset);
CPU_SET((unsigned)cpu, &cpuset);
if (pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset) != 0) {
fprintf(stderr, "WARNING: Failed to set CPU affinity for %s thread to CPU %d.\n", role, cpu);
} else {
fprintf(stderr, "%s thread pinned to CPU %d.\n", role, cpu);
}
}
}
}
}
/* =====================
SPSC Ring Buffer (output path)
===================== */
@@ -798,6 +857,14 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
int i;
struct dongle_state *s = static_cast<dongle_state*>(ctx);
struct demod_state *d = s->demod_target;
/* One-time: ensure the USB callback thread gets RT scheduling/affinity if enabled */
{
static std::atomic<int> usb_sched_applied{0};
int expected = 0;
if (usb_sched_applied.compare_exchange_strong(expected, 1)) {
maybe_set_thread_realtime_and_affinity("USB");
}
}
if (exitflag) {
return;}
@@ -826,6 +893,7 @@ static void rtlsdr_callback(unsigned char *buf, uint32_t len, void *ctx)
static void *dongle_thread_fn(void *arg)
{
struct dongle_state *s = static_cast<dongle_state*>(arg);
maybe_set_thread_realtime_and_affinity("DONGLE");
rtlsdr_read_async(s->dev, rtlsdr_callback, s, 16, s->buf_len);
return 0;
}
@@ -834,6 +902,7 @@ static void *demod_thread_fn(void *arg)
{
struct demod_state *d = static_cast<demod_state*>(arg);
struct output_state *o = d->output_target;
maybe_set_thread_realtime_and_affinity("DEMOD");
while (!exitflag) {
safe_cond_wait(&d->ready, &d->ready_m);
/* Consume from last fully-written input buffer */