Better systrace slices for application startup.
This change adds three new timeslices :
- PostFork : As soon as possible after the app forks from the
zygote. Can be used in conjunction with the system_server
"Start proc:" event to derive an upper bound on fork() and
zygote overhead.
- RuntimeInit & ActivityThreadMain for ZygoteInit#runtimeInit
and ActivityThread#main.
ActivityThread#handleBindApplication and higher level functions
are already well instrumented in systrace. handleBindApplication
should occur immediately after ActivityThread#main.
Note that we use the Activity manager tag to make it easier to
correlate these new events with surrounding events (Start proc
and handleBindApplication) that are already using the AM tag.
bug: 21632700
Change-Id: Ibc01f1721f962c913f3c02a51763b6feb1eb6a4d
diff --git a/core/java/com/android/internal/os/Zygote.java b/core/java/com/android/internal/os/Zygote.java
index 1e7ee5a..4f6d781 100644
--- a/core/java/com/android/internal/os/Zygote.java
+++ b/core/java/com/android/internal/os/Zygote.java
@@ -17,6 +17,7 @@
package com.android.internal.os;
+import android.os.Trace;
import dalvik.system.ZygoteHooks;
import android.system.ErrnoException;
import android.system.Os;
@@ -88,6 +89,13 @@
int pid = nativeForkAndSpecialize(
uid, gid, gids, debugFlags, rlimits, mountExternal, seInfo, niceName, fdsToClose,
instructionSet, appDataDir);
+ // Enable tracing as soon as possible for the child process.
+ if (pid == 0) {
+ Trace.setTracingEnabled(true);
+
+ // Note that this event ends at the end of handleChildProc,
+ Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "PostFork");
+ }
VM_HOOKS.postForkCommon();
return pid;
}
@@ -124,6 +132,10 @@
VM_HOOKS.preFork();
int pid = nativeForkSystemServer(
uid, gid, gids, debugFlags, rlimits, permittedCapabilities, effectiveCapabilities);
+ // Enable tracing as soon as we enter the system_server.
+ if (pid == 0) {
+ Trace.setTracingEnabled(true);
+ }
VM_HOOKS.postForkCommon();
return pid;
}