Coalesce input events that arrive faster than 333Hz. (DO NOT MERGE)

Some drivers report individual finger updates one at a time
instead of all at once.  When 10 fingers are down, this can
cause the framework to have to handle 10 times as many events
each with 10 times as much data.  Applications like
PointerLocation would get significantly bogged down by all
of the redundant samples.

This change coalesces samples that are closely spaced in time,
before they are dispatched, as part of the motion event batching
protocol.

Increased the size of the InputChannel shared memory buffer so
that applications can catch up faster if they accumulate a
backlog of samples.

Change-Id: Ibc6abf8af027d9003011ac75caa12941080caba3

1 files changed, 17 insertions, 0 deletions

diff --git a/services/input/EventHub.cpp b/services/input/EventHub.cpp
index 7625adb14108..d80abe895b5f 100644
--- a/services/input/EventHub.cpp
+++ b/services/input/EventHub.cpp
@@ -539,7 +539,24 @@ size_t EventHub::getEvents(int timeoutMillis, RawEvent* buffer, size_t bufferSiz
                                 (int) iev.time.tv_sec, (int) iev.time.tv_usec,
                                 iev.type, iev.code, iev.value);
 
+#ifdef HAVE_POSIX_CLOCKS
+                        // Use the time specified in the event instead of the current time
+                        // so that downstream code can get more accurate estimates of
+                        // event dispatch latency from the time the event is enqueued onto
+                        // the evdev client buffer.
+                        //
+                        // The event's timestamp fortuitously uses the same monotonic clock
+                        // time base as the rest of Android.  The kernel event device driver
+                        // (drivers/input/evdev.c) obtains timestamps using ktime_get_ts().
+                        // The systemTime(SYSTEM_TIME_MONOTONIC) function we use everywhere
+                        // calls clock_gettime(CLOCK_MONOTONIC) which is implemented as a
+                        // system call that also queries ktime_get_ts().
+                        event->when = nsecs_t(iev.time.tv_sec) * 1000000000LL
+                                + nsecs_t(iev.time.tv_usec) * 1000LL;
+                        LOGV("event time %lld, now %lld", event->when, now);
+#else
                         event->when = now;
+#endif
                         event->deviceId = deviceId;
                         event->type = iev.type;
                         event->scanCode = iev.code;