[PATCH] x86: Add --enable-rdtscp-in-benchtests

[Siddhesh Poyarekar]

On 23/10/18 4:28 PM, H.J. Lu wrote:
> On 10/23/18, Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
>> On 23/10/18 2:34 PM, Florian Weimer wrote:
>>> Shouldn't the benchtests use clock_gettime anyway, to avoid issues in
>>> case the TSC is not synchronized across cores?
>>
>> There's an option USE_CLOCK_GETTIME to make benchtests do that, but
>> otherwise it uses the hp_timing bits by default.
> 
> I want something better that rdtsc and very low overhead since some bench
> tests only last a few cycles.  Adding lfence may make timing data look like
> noise.

Is the configure option necessary?  You could just add a Makefile option 
in benchtests similar to USE_CLOCK_GETTIME and then document it in 
benchtests/README.

Siddhesh