From 045daaf191f94fb124f5d232d6935566cca81e91 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <andrew@tridgell.net>
Date: Wed, 1 Dec 2021 21:25:46 +1100
Subject: [PATCH] AP_Logger: speed up logging of crash_dump.bin

dump 450k crash log in about 1 minute
---
 libraries/AP_Logger/AP_Logger.cpp | 20 +++++++++++++++++---
 libraries/AP_Logger/AP_Logger.h   |  2 ++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/libraries/AP_Logger/AP_Logger.cpp b/libraries/AP_Logger/AP_Logger.cpp
index f834e16900..aba112ad51 100644
--- a/libraries/AP_Logger/AP_Logger.cpp
+++ b/libraries/AP_Logger/AP_Logger.cpp
@@ -1312,9 +1312,7 @@ void AP_Logger::io_thread(void)
             hal.util->log_stack_info();
         }
 #if HAL_LOGGER_FILE_CONTENTS_ENABLED
-        if (counter % 100 == 0) {
-            file_content_update();
-        }
+        file_content_update();
 #endif
     }
 }
@@ -1442,6 +1440,18 @@ void AP_Logger::file_content_update(void)
         return;
     }
 
+    /* this function is called at max 1kHz. We don't want to saturate
+       the logging with file data, so we reduce the frequency of 64
+       byte file writes by a factor of 100. For the file
+       crash_dump.bin we dump 10x faster so we get it in a reasonable
+       time (full dump of 450k in about 1 minute)
+    */
+    file_content.counter++;
+    const uint8_t frequency = file_content.fast?10:100;
+    if (file_content.counter % frequency != 0) {
+        return;
+    }
+
     // remove a file structure from the linked list
     auto remove_from_list = [this,file]()
     { 
@@ -1458,11 +1468,15 @@ void AP_Logger::file_content_update(void)
     if (file_content.fd == -1) {
         // open a new file
         file_content.fd  = AP::FS().open(file->filename, O_RDONLY);
+        file_content.fast = strncmp(file->filename, "@SYS/crash_dump", 15) == 0;
         if (file_content.fd == -1) {
             remove_from_list();
             return;
         }
         file_content.offset = 0;
+        if (file_content.fast) {
+            GCS_SEND_TEXT(MAV_SEVERITY_INFO, "Logging %s", file->filename);
+        }
     }
 
     struct log_File pkt {
diff --git a/libraries/AP_Logger/AP_Logger.h b/libraries/AP_Logger/AP_Logger.h
index 7be276a04c..e3075e4de4 100644
--- a/libraries/AP_Logger/AP_Logger.h
+++ b/libraries/AP_Logger/AP_Logger.h
@@ -559,6 +559,8 @@ private:
         struct file_list *head, *tail;
         int fd;
         uint32_t offset;
+        bool fast;
+        uint8_t counter;
         HAL_Semaphore sem;
     } file_content;
     void file_content_update(void);