From a75db1286dd34cc10ebf32f6694307f30ca28496 Mon Sep 17 00:00:00 2001
From: Daniel Agar <daniel@agar.ca>
Date: Mon, 26 Aug 2024 13:24:39 -0400
Subject: [PATCH] logger: automatically limit buffer size to largest available
 free chunk (NuttX only)

---
 src/modules/logger/log_writer_file.cpp | 40 +++++++++++++++++++++-----
 src/modules/logger/log_writer_file.h   |  6 ++--
 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/src/modules/logger/log_writer_file.cpp b/src/modules/logger/log_writer_file.cpp
index 50d5cf7f45..2001baf2f6 100644
--- a/src/modules/logger/log_writer_file.cpp
+++ b/src/modules/logger/log_writer_file.cpp
@@ -42,9 +42,11 @@
 #include <px4_platform_common/posix.h>
 #include <px4_platform_common/crypto.h>
 #include <px4_platform_common/log.h>
-#ifdef __PX4_NUTTX
-#include <systemlib/hardfault_log.h>
-#endif /* __PX4_NUTTX */
+
+#if defined(__PX4_NUTTX)
+# include <malloc.h>
+# include <systemlib/hardfault_log.h>
+#endif // __PX4_NUTTX
 
 using namespace time_literals;
 
@@ -60,11 +62,13 @@ LogWriterFile::LogWriterFile(size_t buffer_size)
 	//We always write larger chunks (orb messages) to the buffer, so the buffer
 	//needs to be larger than the minimum write chunk (300 is somewhat arbitrary)
 	{
-		math::max(buffer_size, _min_write_chunk + 300),
+		buffer_size,
+		_min_write_chunk + 300,
 		perf_alloc(PC_ELAPSED, "logger_sd_write"), perf_alloc(PC_ELAPSED, "logger_sd_fsync")},
 
 	{
 		300, // buffer size for the mission log (can be kept fairly small)
+		1,
 		perf_alloc(PC_ELAPSED, "logger_sd_write_mission"), perf_alloc(PC_ELAPSED, "logger_sd_fsync_mission")}
 }
 {
@@ -590,9 +594,12 @@ const char *log_type_str(LogType type)
 	return "unknown";
 }
 
-LogWriterFile::LogFileBuffer::LogFileBuffer(size_t log_buffer_size, perf_counter_t perf_write,
-		perf_counter_t perf_fsync)
-	: _buffer_size(log_buffer_size), _perf_write(perf_write), _perf_fsync(perf_fsync)
+LogWriterFile::LogFileBuffer::LogFileBuffer(size_t log_buffer_desired_size, size_t log_buffer_min_size,
+		perf_counter_t perf_write, perf_counter_t perf_fsync) :
+	_buffer_size(log_buffer_desired_size),
+	_buffer_size_min(log_buffer_min_size),
+	_perf_write(perf_write),
+	_perf_fsync(perf_fsync)
 {
 }
 
@@ -660,6 +667,25 @@ bool LogWriterFile::LogFileBuffer::start_log(const char *filename)
 	}
 
 	if (_buffer == nullptr) {
+		_buffer_size = math::max(_buffer_size, _buffer_size_min);
+
+#if defined(__PX4_NUTTX)
+		struct mallinfo alloc_info = mallinfo();
+
+		// reduced to largest available free chunk, but leave at least 1 kB available
+		static constexpr ssize_t one_kb = 1024;
+		const ssize_t reduced_buffer_size = math::max((alloc_info.mxordblk - one_kb) / one_kb * one_kb,
+						    (ssize_t)_buffer_size_min);
+
+		if ((reduced_buffer_size > 0) && ((ssize_t)_buffer_size > reduced_buffer_size)) {
+			PX4_WARN("requested buffer size %dB limited to available %dB (available plus 1 kB margin)",
+				 _buffer_size, reduced_buffer_size);
+
+			_buffer_size = reduced_buffer_size;
+		}
+
+#endif // __PX4_NUTTX
+
 		_buffer = (uint8_t *) px4_cache_aligned_alloc(_buffer_size);
 
 		if (_buffer == nullptr) {
diff --git a/src/modules/logger/log_writer_file.h b/src/modules/logger/log_writer_file.h
index 757f69de25..7654878938 100644
--- a/src/modules/logger/log_writer_file.h
+++ b/src/modules/logger/log_writer_file.h
@@ -169,7 +169,8 @@ private:
 	class LogFileBuffer
 	{
 	public:
-		LogFileBuffer(size_t log_buffer_size, perf_counter_t perf_write, perf_counter_t perf_fsync);
+		LogFileBuffer(size_t log_buffer_desired_size, size_t log_buffer_min_size,
+			      perf_counter_t perf_write, perf_counter_t perf_fsync);
 
 		~LogFileBuffer();
 
@@ -203,7 +204,8 @@ private:
 		bool _should_run = false;
 		px4::atomic_bool _had_write_error{false};
 	private:
-		const size_t _buffer_size;
+		size_t _buffer_size;
+		const size_t _buffer_size_min;
 		int	_fd = -1;
 		uint8_t *_buffer = nullptr;
 		size_t _head = 0; ///< next position to write to