diff --git a/runtime/vm/log.cc b/runtime/vm/log.cc
index 83b99b20f07..c7c4c2ffe9a 100644
--- a/runtime/vm/log.cc
+++ b/runtime/vm/log.cc
@@ -12,6 +12,15 @@ namespace dart {
 
 DEFINE_FLAG(bool, force_log_flush, false, "Always flush log messages.");
 
+// The following flag is useful when debugging on Android, since
+// adb logcat truncates messages that are "too long" (and always
+// flushing would result in too many short messages).
+DEFINE_FLAG(
+    int,
+    force_log_flush_at_size,
+    0,
+    "Flush log messages when buffer exceeds given size (disabled when 0).");
+
 DEFINE_FLAG(charp,
             isolate_log_filter,
             NULL,
@@ -80,7 +89,7 @@ void Log::VPrint(const char* format, va_list args) {
   }
   free(buffer);
 
-  if ((manual_flush_ == 0) || FLAG_force_log_flush) {
+  if (ShouldFlush()) {
     Flush();
   }
 }
@@ -161,6 +170,12 @@ void Log::DisableManualFlush(const intptr_t cursor) {
   }
 }
 
+bool Log::ShouldFlush() const {
+  return ((manual_flush_ == 0) || FLAG_force_log_flush ||
+          ((FLAG_force_log_flush_at_size > 0) &&
+           (cursor() > FLAG_force_log_flush_at_size)));
+}
+
 void LogBlock::Initialize() {
   log_->EnableManualFlush();
 }
diff --git a/runtime/vm/log.h b/runtime/vm/log.h
index 8c851a436a2..c18d6f58673 100644
--- a/runtime/vm/log.h
+++ b/runtime/vm/log.h
@@ -54,6 +54,9 @@ class Log {
   void EnableManualFlush();
   void DisableManualFlush(const intptr_t cursor);
 
+  // Returns true when flush is required.
+  bool ShouldFlush() const;
+
   // Returns false if we should drop log messages related to 'isolate'.
   static bool ShouldLogForIsolate(const Isolate* isolate);