Re: architecture paper draft

[William Cohen <wcohen at redhat dot com>]

Chen, Brad wrote:
> Vara has identified two basic kinds of taps:
> - program-counter based
> - interrupt based

Additional ones to think about:

-data memory locations accesses
	track changes to value or determine functions modifying val

	use hardware support in processor to watch location


-taps based on function pointers in data structures
	lots of the ABIs in the kernel use data structures to describe operations.

> These makes sense from the perspective of the Systemtap 
> implementor. From the perspective of the script writer, 
> they will likely be thinking about source-code constructs 
> rather than machine code:
> - procedures (before, after, etc.). This is the "systemtapset", right?
> - source-code features (call sites, line numbers, labels)
> - software events (synchronous)
> - hardware events (asynchronous)
> I think the first three would be program-counter based and
> the fourth would be interrupt based. So part of the design 
> ought to be considering both the implementation perspective 
> and the constructs that script writers would think about.
>
> A third type I'd add to Vara's list is "compound taps".
> For example, a subset of scheduler-related taps from the 
> systemtapset might be used as a part of the scheduler
> tap set. You might also have a compound tap that was a
> existing tap plus a condition, such as a procstatechange()
> event when NewState==PROC_READY.
>
> Brad