Tweaks to perf jitdump support

runtime/vm/os_linux.cc

Index: runtime/vm/os_linux.cc
diff --git a/runtime/vm/os_linux.cc b/runtime/vm/os_linux.cc
index 1e6398ad48f6676c05eb28d0b718f658ad9c7c54..efa2c56dd4c8812fd621a41946b7d90880997166 100644
--- a/runtime/vm/os_linux.cc
+++ b/runtime/vm/os_linux.cc
@@ -152,11 +152,11 @@ class JitdumpCodeObserver : public CodeObserver {
       return;
     }
     // The Jitdump code observer writes all jitted code into
-    // /tmp/jit-<pid>.dump, we open the file once on initialization and close
+    // ./perf-<pid>.jitdump, we open the file once on initialization and close
     // it when the VM is going down.
     {
       // Open the file.
-      const char* format = "/tmp/jit-%" Pd ".dump";
+      const char* format = "perf-%" Pd ".jitdump";

[Vyacheslav Egorov (Google), 2014/08/20 20:14:39]

perf is writing output into perf.data so I think we should just remove the PID
mangling altogether here.

       intptr_t pid = getpid();
       intptr_t len = OS::SNPrint(NULL, 0, format, pid);
       char* filename = new char[len + 1];