Re: [patch 2/3] Latencytop instrumentations part 1

[Arjan van de Ven]

Frank Ch. Eigler wrote:
> Hi -
>
> On Fri, Jan 18, 2008 at 02:33:34PM -0800, Arjan van de Ven wrote:
> > [...]
> > > Can you suggest of some reason why all this instrumentation could
> > > not be in the form of standard markers (perhaps conditionally
> > > compiled out if necessary)?
> > sure. Every instrumentation you see is of the nested kind (since the lowest level
> > of nesting is already automatic via wchan).
> > If markers can provide me the following semantics, I'd be MORE than happy to use markers:
> > [...]
> > If markers can provide that semantics ... you sold me.
>
> Further to what acme said, markers are semantics-free.  Callback
> functions that implement your entry & exit semantics can be attached
> at run time, at your pleasure.  (So can systemtap probes, for that
> matter.)  The main difference would be that these callback functions
> would have manage the per-thread LIFO data structures themselves,
> instead of allocating backpointers on the kernel stack.  (Bonus marks
> for not modifying task_struct. :-)

modifying task struct to have storage space is no big deal...
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/