system/core: Add initial implementation of the bootstat command.

The bootstat command enables the measurement and logging of boot time
metrics
for GMS devices.

BUG:21724738
Change-Id: I331456dd38a60fb4ef24a4d5320909dbad30db66

1 files changed, 47 insertions, 0 deletions

diff --git a/bootstat/README.md b/bootstat/README.md
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+# bootstat #
+
+The bootstat command records boot events (e.g., `firmware_loaded`,
+`boot_complete`) and the relative time at which these events occurred. The
+command also aggregates boot event metrics locally and logs the metrics for
+analysis.
+
+    Usage: bootstat [options]
+    options include:
+      -d              Dump the boot event records to the console.
+      -h              Show this help.
+      -l              Log all metrics to logstorage.
+      -r              Record the relative time of a named boot event.
+
+## Relative time ##
+
+The timestamp recorded by bootstat is the uptime of the system, i.e., the
+number of seconds since the system booted.
+
+## Recording boot events ##
+
+To record the relative time of an event during the boot phase, call `bootstat`
+with the `-r` option and the name of the boot event.
+
+    $ bootstat -r boot_complete
+
+The relative time at which the command runs is recorded along with the name of
+the boot event to be persisted.
+
+## Logging boot events ##
+
+To log the persisted boot events, call `bootstat` with the `-l` option.
+
+    $ bootstat -l
+
+bootstat logs all boot events recorded using the `-r` option to the EventLog
+using the Tron histogram. On GMS devices these logs are uploaded via Clearcut
+for aggregation and analysis.
+
+## Printing boot events ##
+
+To print the set of persisted boot events, call `bootstat` with the `-p` option.
+
+    $ bootstat -p
+    Boot events:
+    ------------
+    boot_complete   71
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