From 4519aa886774f693f9e2fc28242c98d9fa1a57e8 Mon Sep 17 00:00:00 2001
From: Andrew Tridgell <tridge@samba.org>
Date: Thu, 2 Jan 2014 22:04:22 +1100
Subject: [PATCH] DataFlash: only fsync every 10 seconds

prevents too much work in SITL
---
 libraries/DataFlash/DataFlash_File.cpp | 5 ++++-
 libraries/DataFlash/DataFlash_File.h   | 1 +
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/libraries/DataFlash/DataFlash_File.cpp b/libraries/DataFlash/DataFlash_File.cpp
index b13e39b0f2..6d7f8bd61e 100644
--- a/libraries/DataFlash/DataFlash_File.cpp
+++ b/libraries/DataFlash/DataFlash_File.cpp
@@ -531,8 +531,11 @@ void DataFlash_File::_io_timer(void)
         _write_fd = -1;
         _initialised = false;
     } else {
-        ::fsync(_write_fd);
         BUF_ADVANCEHEAD(_writebuf, nwritten);
+        if (hal.scheduler->millis() - last_fsync_ms > 10000) {
+            last_fsync_ms = hal.scheduler->millis();
+            ::fsync(_write_fd);            
+        }
     }
 }
 
diff --git a/libraries/DataFlash/DataFlash_File.h b/libraries/DataFlash/DataFlash_File.h
index 03fbf55aad..ea5a001da6 100644
--- a/libraries/DataFlash/DataFlash_File.h
+++ b/libraries/DataFlash/DataFlash_File.h
@@ -49,6 +49,7 @@ private:
     uint32_t _read_offset;
     volatile bool _initialised;
     const char *_log_directory;
+    uint32_t last_fsync_ms;
 
     /*
       read a block