Re: [PATCH] perf/x86/intel/pt: Allow disabling branch tracing

Alexander Shishkin
2017-02-06T16:06:14Z

Andi Kleen <andi@firstfloor.org> writes:

> Alexander Shishkin <alexander.shishkin@linux.intel.com> writes:
>
>> Now that Intel PT supports more types of trace content than just branch
>> tracing, it may be useful to allow the user to disable branch tracing
>> when it is not needed.
>>
>> The special case is BDW, where not setting BranchEn is not supported.
>>
>> This is slightly trickier than necessary, because up to this moment
>> the driver has been setting BranchEn automatically and the userspace
>> assumes as much. Instead of reversing the semantics of BranchEn, we
>> introduce a 'passthrough' bit, which will forego the default and allow
>> the user to set BranchEn to their heart's content.
>
> cpu/passthrough=1,branchen=1/ seems far uglier/more complicanted to me
> than the original cpu/nobranch=1/

It's /passthrough=1,branch=0/ or simply /passthrough=1/.

Regards,
--
Alex