Re: [PATCH V4 10/16] perf, core: simplify need branch stack check

[Stephane Eranian]

On Wed, Jul 2, 2014 at 12:57 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Mon, Jun 30, 2014 at 04:50:47PM +0800, Yan, Zheng wrote:
>> event->attr.branch_sample_type is non-zero no matter branch stack
>> is enabled explicitly or is enabled implicitly. we can use it to
>> replace intel_pmu_needs_lbr_smpl(). This avoids duplicating code
>> that implicitly enables the LBR.
>
> How so? I grep'ed for a minute but could not find what you're referring
> to.

If !(attr->sample_type & PERF_SAMPLE_BRANCH_STACK), then
event->attr.branch_type = 0. If the sample_type is set, then branch_type
is necessarily non-zero.
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