am b10e562b: Merge "Introduce a mechanism to trace boot sequence."

* commit 'b10e562b4cb5ffd6f02ab891d40644b581ad5d47':
  Introduce a mechanism to trace boot sequence.

init/readme.txt

@@ -377,6 +377,29 @@ system_server: 15350 15150 (-200)
 bootanimation ends at: 33790 31230 (-2560)
 
 
+Systrace
+--------
+Systrace [1] can be used for obtaining performance analysis reports during boot
+time on userdebug or eng builds.
+Here is an example of trace events of "wm" and "am" categories:
+
+  $ANDROID_BUILD_TOP/external/chromium-trace/systrace.py wm am --boot
+
+This command will cause the device to reboot. After the device is rebooted and
+the boot sequence has finished, the trace report is obtained from the device
+and written as trace.html on the host by hitting Ctrl+C.
+
+LIMITATION
+Recording trace events is started after persistent properties are loaded, so
+the trace events that are emitted before that are not recorded. Several
+services such as vold, surfaceflinger, and servicemanager are affected by this
+limitation since they are started before persistent properties are loaded.
+Zygote initialization and the processes that are forked from the zygote are not
+affected.
+
+[1] http://developer.android.com/tools/help/systrace.html
+
+
 Debugging init
 --------------
 By default, programs executed by init will drop stdout and stderr into

rootdir/init.rc

@@ -259,6 +259,7 @@ on post-fs-data
     chmod 0660 /data/misc/wifi/wpa_supplicant.conf
     mkdir /data/local 0751 root root
     mkdir /data/misc/media 0700 media media
+    mkdir /data/misc/boottrace 0771 system shell
 
     # For security reasons, /data/local/tmp should always be empty.
     # Do not place files or directories in /data/local/tmp

rootdir/init.trace.rc

@@ -33,3 +33,11 @@ on boot
 # Allow only the shell group to read and truncate the kernel trace.
     chown root shell /sys/kernel/debug/tracing/trace
     chmod 0660 /sys/kernel/debug/tracing/trace
+
+on property:persist.debug.atrace.boottrace=1
+    start boottrace
+
+# Run atrace with the categories written in a file
+service boottrace /system/bin/atrace --async_start -f /data/misc/boottrace/categories
+    disabled
+    oneshot