Merge "Add a README.md for async_safe"
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+# async_safe logging
+
+This library provides an async_safe implementation for formatting and writing log messages to logd.
+
+Note that the liblog implementation connects a single socket to logd and uses a RWLock to manage
+it among threads, whereas these functions connect to liblog for each log message. While it's
+beneficial to have this lock-free and therefore async_safe mechanism to write to logd, connecting
+a socket for each message does not scale well under load. It was also determined to be too
+costly to connect a socket for each thread as some processes, such as system_server, have over 100
+threads. Therefore, we maintain these two separate mechanisms.