relayfs changes needed

[Gui,Jian]

> So if this is the case, I'm wondering if maybe the right thing to do is
> to remove all sequence numbers, formatting, and merging in the transport
> layer for relayfs and simply let it run full-speed dumping data into
> per-cpu files. This gives the highest performance and moves the
> responsibility for any merging or other postprocessing to the
> application layer, where it can be done most efficiently. So some script
> (or program) will invoke systemtap, and on exit, take the binary data
> files and process them. Systemtap will not timestamp, sequence, or
> otherwise process the data. 
> 
How about adding an option to control this? 
e.g.
  "stap -b -K a.stp" will write to relayfs buffer directly, remove all 
sequence numbers and keep the pre-cpu files;
  "stap -b a.stp" will also write to relayfs buffer directly, but 
still keep current plain ascii sequencing scheme and merge pre-cpu files
to probe.out as it does now.

I think it can keep the convenience of current sequencing method 
in cases where ascii tracing is good enough, and also keep the
performance advantage of relayfs.