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SubjectRe: [RFC][PATCH] perf tools: Merge trace.info content into perf.data

* Ingo Molnar <mingo@elte.hu> wrote:

> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
>
> > Hi,
> >
> > Here is an attempt to remove the trace.info file. It works well for
> > me, the reason for it to be an RFC is that I have doubts about the
> > backward compatibility.
> >
> > A file created by perf after his patch is unsupported by previous
> > version because the size of the headers have increased.
>
> That's OK i think in terms of trace.info - trace.info was a temporary
> hack to begin with.
>
> > That said, it's two new fields that have been added in the end of the
> > headers, and those could be ignored by previous versions if they just
> > handled the dynamic header size and then ignore the unknow part. The
> > offsets guarantee the compatibility.
>
> Yes, that's how it should work.
>
> > But previous versions handle the header size using its static size,
> > not dynamic, then it's not backward compatible.
> >
> > Anyway, I'm not sure exactly how to handle that.
>
> That's a bug in the previous version - mind doing a standalone fix for
> that so we can mark it Cc: stable?

Meanwhile i've applied your two patches - they are clear steps forward.
We'll need the -stable fix so that the new perf.data can be read. (and
even that only affects -R afaics - so normal perf record / perf report
is compatible.)

Btw., we also need a patch for new perf to read older perf.data files
[non-trace.info ones], as those are not working either:

$ perf report
Fatal: incompatible file format

( We dont want to push it - i.e. i dont think we need to support old
perf.data + trace.info combos. )

Ingo


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