Re: comments on Performance Counters for Linux (PCL)

From: Peter Zijlstra
Date: Fri May 29 2009 - 16:33:22 EST

On Thu, 2009-05-28 at 18:25 +0200, Peter Zijlstra wrote:
> > 10/ Group event buffer entry
> >
> > This is activated by setting the PERF_RECORD_GROUP in the record_type
> > field. With this bit set, the values of the other members of the
> > group are stored sequentially in the buffer. To help figure out which
> > value corresponds to which event, the current implementation also
> > stores the raw encoding of the event.
> >
> > The event encoding does not help figure out which event the value refers
> > to. There can be multiple events with the same code. This does fit the
> > API model where events are identified by file descriptors.
> >
> > The file descriptor must be provided and not the raw encoding.
> OK, sounds sensible.

This can't actually be done, fds can change, and there is no struct
file* to fd map.

If the config isn't good enough, the best we could do is something
unique per instance.

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