Re: [Question] perf header: Why the HEADER_EVENT_DESC is needed?

From: Stephane Eranian
Date: Sat Jul 21 2012 - 13:16:08 EST

On Sat, Jul 21, 2012 at 1:11 PM, Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> Hi Stephane,
> I wonder why we need to save the event descriptions in the feature area
> of file header. Since the perf_event_attr, its ids and the event name
> are already saved in the header, it seems a duplicate work to do that.
> For printing the information, we might reuse those info or evlist
> directly IMHO.
> Am I missing something?

Unfortunately, I think you are.

There event names are not saved in header.c except indirectly by write_cmdline.
But more importantly, event_desc makes it possible to connect an event name as
passed on the cmdline with the corresponding attr struct.

Furthermore, it is also present in pipe mode, with the patch I posted
months ago.

Finally, you cannot arbitrarily remove features like this. We do have
tools that do
rely on the presence of EVENT_DESC.
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