Re: [PATCH V7 13/17] perf, x86: enable LBR callstack when recording callchain

[Peter Zijlstra]

On Wed, Nov 05, 2014 at 03:53:34PM +0000, Liang, Kan wrote:
> > I don't think it would be very hard to modify the patch set to make that 3rd
> > mode visible. Just need to make that new PERF_RECORD_* type visible to
> > user and modify the compatibility checks.
> 
> It's not hard. But LBR is not an independent callchain options. It's better to be
> a supplement of FP. Otherwise, it may confuse the user. He enables the
> BRANCH_CALL_STACK, but the data is partly or even not at all from hardware.

What the user sees is up to userspace. It should not be forced by the
kernel/user interface.
--
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/