Re: [PATCH 1/2] perf tools: Add reference timestamp to perf header

From: Frederic Weisbecker
Date: Mon Dec 13 2010 - 12:15:48 EST


On Mon, Dec 13, 2010 at 06:11:29PM +0100, Peter Zijlstra wrote:
> On Mon, 2010-12-13 at 18:09 +0100, Frederic Weisbecker wrote:
> >
> >
> > Right, but Peter wanted us to get rid of these user events types.
>
> Yes they suck.
>
> > I guess we can't really do this as new perf tools must be able
> > to support old perf files.
>
> Preferably, yes, but I don't see why we can't break the data file format
> if we've got good reasons to.

IMO we should prioritize the backward compatibility over some little code sanity.
It's worth a very small range of values to reserve in the kernel and we are done.

> > So this should be the last one to add. Something like PERF_RECORD_GEN_EVT
> > that has a field in its headers containing a sub-type which can be this
> > wall clock but can also host about everything in the future.
> >
> > This way we don't propagate more the possible overlap with the kernel.
>
> I don't see why we should add more, that's going the wrong direction.

This must be the last one.
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