AP_Logger: handle instance types in rate limiting

libraries/AP_Logger/AP_Logger_Backend.cpp

@@ -3,6 +3,7 @@
 #include "LoggerMessageWriter.h"
 
 #include <AP_InternalError/AP_InternalError.h>
+#include <AP_Scheduler/AP_Scheduler.h>
 
 extern const AP_HAL::HAL& hal;
 
@@ -672,5 +673,20 @@ bool AP_Logger_RateLimiter::should_log(uint8_t msgid)
             return true;
         }
     }
-    return should_log_streaming(msgid);
+
+    // if we've already decided on sending this msgid in this tick then use the
+    // same decision again
+    const uint16_t sched_ticks = AP::scheduler().ticks();
+    if (sched_ticks == last_sched_count[msgid]) {
+        return last_return.get(msgid);
+    }
+    last_sched_count[msgid] = sched_ticks;
+
+    bool ret = should_log_streaming(msgid);
+    if (ret) {
+        last_return.set(msgid);
+    } else {
+        last_return.clear(msgid);
+    }
+    return ret;
 }

libraries/AP_Logger/AP_Logger_Backend.h

@@ -23,8 +23,17 @@ private:
     // time in ms we last sent this message
     uint16_t last_send_ms[256];
 
-    // mask of message types that are not streaming
+    // the last scheduler counter when we sent a msg.  this allows us
+    // to detect when we are sending a multi-instance message
+    uint16_t last_sched_count[256];
+
+    // mask of message types that are not streaming. This is a cache
+    // to avoid costly calls to structure_for_msg_type
     Bitmask<256> not_streaming;
+
+    // result of last decision for a message. Used for multi-instance
+    // handling
+    Bitmask<256> last_return;
 };
 
 class AP_Logger_Backend