Re: [PATCH 1/6] perf, x86: Basic Haswell LBR call stack support

From: Peter Zijlstra
Date: Tue Oct 23 2012 - 06:11:42 EST


On Tue, 2012-10-23 at 13:41 +0800, Yan, Zheng wrote:
> On 10/22/2012 06:35 PM, Peter Zijlstra wrote:
> > On Mon, 2012-10-22 at 14:11 +0800, Yan, Zheng wrote:
> >> --- a/include/uapi/linux/perf_event.h
> >> +++ b/include/uapi/linux/perf_event.h
> >> @@ -160,8 +160,9 @@ enum perf_branch_sample_type {
> >> PERF_SAMPLE_BRANCH_ABORT = 1U << 7, /* transaction aborts */
> >> PERF_SAMPLE_BRANCH_INTX = 1U << 8, /* in transaction (flag) */
> >> PERF_SAMPLE_BRANCH_NOTX = 1U << 9, /* not in transaction (flag) */
> >> + PERF_SAMPLE_BRANCH_CALL_STACK = 1U << 10, /* call stack */
> >>
> >> - PERF_SAMPLE_BRANCH_MAX = 1U << 10, /* non-ABI */
> >> + PERF_SAMPLE_BRANCH_MAX = 1U << 11, /* non-ABI */
> >> };
> >
> > You add an ABI sample type without mentioning it in your changelog.. I
> > think I'll stop reading here.
> >
> Ok, I will add the ABI change to the change log. Do you think we should hide this
> branch sample type from user?

Possibly not, I haven't really thought about it. But never hide an ABI
change. Explicitly mention it and preferably explain why you felt it
needed to extend the ABI.
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