From 7a0ca85a90e432072a5c31f81ddff06d3406aa8f Mon Sep 17 00:00:00 2001
From: Oliver Jowett <oliver@mutability.co.uk>
Date: Mon, 29 Sep 2014 23:04:58 +0100
Subject: [PATCH] Measure CPU used by the sample processing thread.

---
 Makefile   |  2 +-
 dump1090.c | 10 ++++++++++
 dump1090.h |  3 +++
 mode_s.c   | 14 ++++++++++++++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 6bfe9ee..672ada2 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ EXTRACFLAGS=-DHTMLPATH=\"$(SHAREDIR)\"
 endif
 
 CFLAGS=-O2 -g -Wall -W `pkg-config --cflags librtlsdr`
-LIBS=`pkg-config --libs librtlsdr` -lpthread -lm
+LIBS=`pkg-config --libs librtlsdr` -lpthread -lm -lrt
 CC=gcc
 
 
diff --git a/dump1090.c b/dump1090.c
index 64087f1..39898e3 100644
--- a/dump1090.c
+++ b/dump1090.c
@@ -507,6 +507,13 @@ static void display_stats(void) {
     printf("%d sample blocks processed\n",                    Modes.stat_blocks_processed);
     printf("%d sample blocks dropped\n",                      Modes.stat_blocks_dropped);
 
+    if (Modes.stat_blocks_processed > 0) {
+        long cpu_millis = (long)Modes.stat_cputime.tv_sec*1000L + Modes.stat_cputime.tv_nsec/1000000L;
+        long sample_millis = Modes.stat_blocks_processed * MODES_ASYNC_BUF_SAMPLES / (Modes.oversample ? 2400 : 2000);
+        printf("%ld ms CPU time used to process %ld ms samples, %.1f%% load\n",
+               cpu_millis, sample_millis, 100.0 * cpu_millis / sample_millis);
+    }
+
     printf("%d ModeA/C detected\n",                           Modes.stat_ModeAC);
     printf("%d Mode-S preambles with poor correlation\n",     Modes.stat_preamble_no_correlation);
     printf("%d Mode-S preambles with noise in the quiet period\n", Modes.stat_preamble_not_quiet);
@@ -549,6 +556,9 @@ static void display_stats(void) {
     printf("%d total usable messages\n",                      Modes.stat_goodcrc + Modes.stat_ph_goodcrc + Modes.stat_fixed + Modes.stat_ph_fixed);
     fflush(stdout);
 
+    Modes.stat_cputime.tv_sec = 0;
+    Modes.stat_cputime.tv_nsec = 0;
+
     Modes.stat_blocks_processed =
         Modes.stat_blocks_dropped = 0;
 
diff --git a/dump1090.h b/dump1090.h
index 97d3ef8..7b9deba 100644
--- a/dump1090.h
+++ b/dump1090.h
@@ -57,6 +57,7 @@
     #include <ctype.h>
     #include <sys/stat.h>
     #include <sys/ioctl.h>
+    #include <time.h>
     #include "rtl-sdr.h"
     #include "anet.h"
 #else
@@ -387,6 +388,8 @@ struct {                             // Internal state
 
     unsigned int stat_blocks_processed;
     unsigned int stat_blocks_dropped;
+
+    struct timespec stat_cputime;
 } Modes;
 
 // The struct we use to store information about a decoded message.
diff --git a/mode_s.c b/mode_s.c
index 20428b6..9dcd7a2 100644
--- a/mode_s.c
+++ b/mode_s.c
@@ -2082,6 +2082,9 @@ void detectModeS_oversample(uint16_t *m, uint32_t mlen) {
     unsigned char msg[MODES_LONG_MSG_BYTES], *pMsg;
     uint32_t j;
 
+    struct timespec cpu_start_time, cpu_end_time;
+    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &cpu_start_time);
+
     memset(&mm, 0, sizeof(mm));
 
     for (j = 0; j < mlen; j++) {
@@ -2412,6 +2415,17 @@ void detectModeS_oversample(uint16_t *m, uint32_t mlen) {
         }
     }
 
+    clock_gettime(CLOCK_THREAD_CPUTIME_ID, &cpu_end_time);
+    Modes.stat_cputime.tv_sec += (cpu_end_time.tv_sec - cpu_start_time.tv_sec);
+    Modes.stat_cputime.tv_nsec += (cpu_end_time.tv_nsec - cpu_start_time.tv_nsec);
+    if (Modes.stat_cputime.tv_nsec < 0) {
+        Modes.stat_cputime.tv_nsec += 1000000000L;
+        Modes.stat_cputime.tv_sec--;
+    } else if (Modes.stat_cputime.tv_nsec > 1000000000L) {
+        Modes.stat_cputime.tv_nsec -= 1000000000L;
+        Modes.stat_cputime.tv_sec++;
+    }
+
     //Send any remaining partial raw buffers now
     if (Modes.rawOutUsed || Modes.beastOutUsed)
       {